ORC1

Existing Annotations Review

Core Functions

ORC1 specifically recognizes and binds ARS consensus sequences (ACS) at chromosomal replication origins through its DBD domain. This is the initiating event for all replication origin function.

Molecular Function:

DNA replication origin binding

Directly Involved In:

DNA replication initiation

Supporting Evidence:

PMID:16824194
Reconstitution of Saccharomyces cerevisiae prereplicative complex assembly in vitro

ORC1 catalyzes ATP hydrolysis, which provides the energy for conformational changes required for origin binding, MCM loading, and complex assembly during pre-RC formation at G1.

Molecular Function:

ATP hydrolysis activity

Directly Involved In:

pre-replicative complex assembly involved in nuclear cell cycle DNA replication

In Complex:

nuclear origin of replication recognition complex

Supporting Evidence:

file:yeast/ORC1/ORC1-deep-research-falcon.md
Orc1 is the only ORC subunit experimentally demonstrated to have ATPase activity

ORC1s BAH domain mediates specific nucleosome binding, which facilitates proper nucleosome positioning at replication origins and coordinates chromatin organization with replication initiation.

Molecular Function:

nucleosome binding

Directly Involved In:

nucleosome organization

Supporting Evidence:

PMID:31263106
Structure and function of the Orc1 BAH-nucleosome complex

References

GO_REF:0000002

Gene Ontology annotation through association of InterPro records with GO terms

GO_REF:0000033

Annotation inferences using phylogenetic trees

GO_REF:0000043

Gene Ontology annotation based on UniProtKB/Swiss-Prot keyword mapping

GO_REF:0000044

Gene Ontology annotation based on UniProtKB/Swiss-Prot Subcellular Location vocabulary mapping, accompanied by conservative changes to GO terms applied by UniProt

GO_REF:0000117

Electronic Gene Ontology annotations created by ARBA machine learning models

GO_REF:0000120

Combined Automated Annotation using Multiple IEA Methods

PMID:8622770

Role of interactions between the origin recognition complex and SIR1 in transcriptional silencing.

PMID:9038340

Coordinate binding of ATP and origin DNA regulates the ATPase activity of the origin recognition complex.

PMID:9335335

Components and dynamics of DNA replication complexes in S. cerevisiae: redistribution of MCM proteins and Cdc45p during S phase.

PMID:9372948

Architecture of the yeast origin recognition complex bound to origins of DNA replication.

PMID:9554851

Formation of a preinitiation complex by S-phase cyclin CDK-dependent loading of Cdc45p onto chromatin.

PMID:11168584

Interactions between Mcm10p and other replication factors are required for proper initiation and elongation of chromosomal DNA replication in Saccharomyces cerevisiae.

PMID:12897051

Differential DNA affinity specifies roles for the origin recognition complex in budding yeast heterochromatin.

PMID:16429126

Proteome survey reveals modularity of the yeast cell machinery.

PMID:16554755

Global landscape of protein complexes in the yeast Saccharomyces cerevisiae.

PMID:16581798

Structure and function of the Saccharomyces cerevisiae Sir3 BAH domain.

PMID:16716188

Cell cycle execution point analysis of ORC function and characterization of the checkpoint response to ORC inactivation in Saccharomyces cerevisiae.

PMID:16824194

Reconstitution of Saccharomyces cerevisiae prereplicative complex assembly in vitro.

PMID:17825064

Interaction between ORC and Cdt1p of Saccharomyces cerevisiae.

PMID:17825065

Yeast two-hybrid analysis of the origin recognition complex of Saccharomyces cerevisiae: interaction between subunits and identification of binding proteins.

PMID:18647841

The architecture of the DNA replication origin recognition complex in Saccharomyces cerevisiae.

PMID:21179020

Defining the budding yeast chromatin-associated interactome.

PMID:22405012

Cdc6-induced conformational changes in ORC bound to origin DNA revealed by cryo-electron microscopy.

PMID:27107014

An inter-species protein-protein interaction network across vast evolutionary distance.

PMID:31263106

Structure and function of the Orc1 BAH-nucleosome complex.

PMID:37020028

Establishment and function of chromatin organization at replication origins.

PMID:37968396

The social and structural architecture of the yeast protein interactome.

Reactome:R-SCE-9749345

CDT1-mediated loading of MCM2-7 to replication origin in budding yeast

Reactome:R-SCE-9749381

ATP-dependent release of CDT1 from the OCCM complex in budding yeast

Reactome:R-SCE-9749401

CTD1-mediated formation of MCM2-7 double hexamers at the replication origins in budding yeast

file:yeast/ORC1/ORC1-deep-research-falcon.md

Falcon deep research report on ORC1 (yeast)

Orc1 (YML065W; UniProt P54784) is the largest, ~914-aa subunit of the heterohexameric origin recognition complex (ORC, Orc1-6), with an N-terminal BAH domain and a C-terminal AAA+ ATPase region.

"encodes **Origin Recognition Complex subunit 1 (Orc1)**, a ~914-aa protein that is part of the heterohexameric ORC (Orc1–6)"
Orc1 has two separable functional modules: an AAA+ initiator module for ATP-dependent origin recognition/licensing, and an N-terminal BAH chromatin-binding module that mediates nucleosome binding and recruitment to silencing-associated chromatin.

"an **AAA+ initiator module** contributing to ATP-dependent origin recognition/licensing, and an N-terminal **BAH chromatin-binding module** that mediates nucleosome binding and recruitment to silencing-associated chromatin sites"
Orc1 is the only ORC subunit experimentally demonstrated to have ATPase activity, and ATP binding by Orc1 is required for ORC DNA binding, while ATP hydrolysis is not always required for the binding step itself.

"Functional evidence further indicates that **ATP binding by Orc1 is required for ORC DNA binding**, while ATP hydrolysis is not always required for the binding step itself"
ORC binds sequence-defined ARS elements and, with Cdc6 and Cdt1, loads MCM2-7 to form the pre-replicative complex; in early G1 ORC recruits Cdc6 then Cdt1-MCM2-7, loading MCM one hexamer at a time into a head-to-head double hexamer.

"In early G1, ORC (including Orc1) recruits **Cdc6**, then **Cdt1–MCM2–7**, loading MCM one hexamer at a time to form a head-to-head MCM double hexamer"
The Orc1 BAH-nucleosome complex was solved at 3.3 Angstrom, with BAH making extensive contacts to core histones and burying ~1590 square Angstrom of surface; unlike Sir3, Orc1 BAH does not strongly discriminate H4K16 acetylation state.

"A structural study determined the Orc1 BAH–nucleosome complex at **3.3 Å** and reported that Orc1 BAH forms extensive contacts with core histones, **burying ~1590 Å²** of surface"
At HM silencers, the Orc1 BAH domain binds silencer elements and recruits Sir1, which helps recruit the Sir2/Sir3/Sir4 silencing machinery to nucleate heterochromatin.

"Orc1 BAH binds at DNA silencer elements and recruits **Sir1**, which then helps recruit the Sir2/Sir3/Sir4 silencing machinery"
Orc1's origin-binding and silencing-locus-binding determinants are genetically separable: deletion of the BAH domain abolishes binding at silencing-associated sites but Orc1 remains bound to replication origins.

"Orc1 lacking the BAH domain is **lost from silencing-associated sites but remains bound to replication origins**"
Orc1 BAH-nucleosome interactions protect rDNA border integrity during meiosis; reduced Orc1-BAH affinity is associated with increased double-strand breaks.

"Orc1 BAH–nucleosome interactions contribute to genome stability at rDNA borders during meiosis; reduced Orc1-BAH affinity is associated with increased double-strand breaks"
Licensing (MCM loading) is restricted to early G1; after G1, CDK-dependent phosphorylation inhibits re-licensing to prevent rereplication.

"the **licensing reaction (MCM loading)** is concentrated in **early G1**; after G1, **CDK-dependent phosphorylation** inhibits re-licensing to prevent rereplication"
Budding yeast uses sequence-specific ORC recognition at ARS elements, whereas human ORC is more strongly guided by chromatin landscape, so lineage-specific features (e.g. the Orc4 insertion helix) should not be naively extrapolated.

"yeast uses sequence-specific ORC recognition at ARSs, whereas human ORC is more strongly guided by chromatin landscape"

Suggested Experiments

Experiment: Structural analysis of ORC1 bound to both origin DNA and nucleosomes simultaneously to understand coordination

Type: Structural biology (Cryo-EM, X-ray crystallography)

Experiment: Single-molecule studies of MCM loading kinetics with wild-type versus nucleosome-binding deficient ORC1

Type: Biophysics

Experiment: Quantitative analysis of SIR protein recruitment and heterochromatin spreading at silent loci versus origin binding sites

Type: Quantitative cell biology

Deep Research

Falcon

(ORC1-deep-research-falcon.md)

this with annotations you find in gene/protein databases, but these can be outdated or inaccurate. Falcon Edison Scientific Literature 41 citations 1 artifacts 2026-05-30T10:25:02.793323

Edison artifact artifact-00 (text/markdown)

The research report should be a detailed narrative explaining the function, biological processes, and localization of the gene product. Citations should be given for all claims.

You should prioritize authoritative reviews and primary scientific literature when conducting research. You can supplement
this with annotations you find in gene/protein databases, but these can be outdated or inaccurate.

We are specifically interested in the primary function of the gene - for enzymes, what reaction is catalyzed, and what is the substrate specificity? For transporters, what is the substrate? For structural proteins or adapters, what is the broader structural role? For signaling molecules, what is the role in the pathway.

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We are also interested in the signaling or biochemical pathways in which the gene functions. We are less interested in broad pleiotropic effects, except where these elucidate the precise role.

Include evidence where possible. We are interested in both experimental evidence as well as inference from structure, evolution, or bioinformatic analysis. Precise studies should be prioritized over high-throughput, where available.

Research Report: Functional Annotation of ORC1 (UniProt P54784; ORC1/YML065W) in Saccharomyces cerevisiae (S288c)

1) Verification of correct gene/protein target

The literature synthesized here matches the UniProt-provided identity: S. cerevisiae ORC1 (YML065W; UniProt P54784) encodes Origin Recognition Complex subunit 1 (Orc1), a ~914-aa protein that is part of the heterohexameric ORC (Orc1–6) and contains an N-terminal BAH (bromo-adjacent homology) domain and a C-terminal AAA+ ATPase region with a winged-helix domain (WHD) consistent with ORC1-family initiators. This domain architecture and function are repeatedly stated or implied across structural, genome-wide mapping, and mechanistic licensing studies (ioannes2019structureandfunction pages 1-2, chappleboim2024orderedanddisordered pages 1-1, chacin2023establishmentandfunction pages 19-22).

2) Key concepts and definitions (current understanding)

Origin Recognition Complex (ORC) and origin licensing

In eukaryotes, replication origins are “licensed” in G1 by assembling a pre-replicative complex (pre-RC), whose central event is loading the MCM2–7 helicase onto double-stranded DNA as a head-to-head double hexamer (MCM-DH). In budding yeast, ORC binds sequence-defined ARS elements and, together with Cdc6 and Cdt1, loads MCM2–7 to form the pre-RC (tye2023theoriginrecognition pages 1-2). ORC is a large (~400 kDa) heterohexamer (Orc1–6) that recognizes a replication-origin DNA consensus (ARS consensus sequence, ACS) and acts as the platform that seeds helicase loading and replication initiation (parker2017mechanismsandregulation pages 4-6, tye2023theoriginrecognition pages 2-4).

ARS/ACS elements

Budding-yeast replication origins (ARSs) contain a characteristic ~17 bp ARS consensus sequence (ACS); the essential core is often described as an ~11 bp motif (WTTTATRTTTW) (tye2023theoriginrecognition pages 2-4). In a recent review, >400 ARSs are noted genome-wide, with 249 described as having canonical features (tye2023theoriginrecognition pages 2-4).

Orc1 modularity: AAA+ initiator vs BAH chromatin adapter

A key concept for functional annotation is that Orc1 has separable modules: (i) an AAA+ initiator module contributing to ATP-dependent origin recognition/licensing, and (ii) an N-terminal BAH chromatin-binding module that mediates nucleosome binding and recruitment to silencing-associated chromatin sites (chappleboim2024orderedanddisordered pages 5-5, ioannes2019structureandfunction pages 1-2).

3) Primary molecular functions of Orc1 (substrates, activities, and mechanism)

3.1 ATPase and ATP-dependent origin recognition (substrate: ATP; macromolecular substrate: origin dsDNA)

Orc1 is part of the AAA+ ATPase-containing ORC core; mechanistic reviews summarize that Orc1 is the only ORC subunit experimentally demonstrated to have ATPase activity, and that canonical AAA+ features (Walker A/B, arginine finger, composite active sites) help coordinate ATP binding/hydrolysis within initiator assemblies (parker2017mechanismsandregulation pages 4-6). Functional evidence further indicates that ATP binding by Orc1 is required for ORC DNA binding, while ATP hydrolysis is not always required for the binding step itself (geissenhoner2004theroleof pages 25-28). Together, these support a model where Orc1’s ATP-bound state is critical for stable, specific ORC–origin association and for engaging the co-loader Cdc6 during licensing (geissenhoner2004theroleof pages 25-28, parker2017mechanismsandregulation pages 4-6).

High-resolution cryo-EM structures of the ORC·DNA·Cdc6 intermediate provide direct mechanistic detail about ATPase-site configuration: the Orc1·Orc4 ATPase site and Cdc6·Orc1 composite site can adopt inactive/pre-hydrolysis configurations that require additional activation for catalysis, consistent with a regulated ATPase cycle during helicase recruitment/loading (schmidt2022amechanismof pages 1-2).

3.2 DNA binding and origin architecture (substrate: specific dsDNA motifs and local DNA shape)

Budding yeast ORC recognizes origins largely via sequence-defined elements. A 2023 review reports that yeast ORC bound to 72 bp of ARS305 DNA (ACS + B1) was solved at 3.0 Å by cryo-EM, with Orc1–5 encircling DNA; Orc6 is positioned away from the main DNA-encircling module (tye2023theoriginrecognition pages 2-4). The same review describes base-specific and non-specific components of DNA recognition: Orc1 and Orc2 contribute minor-groove interactions (e.g., Orc1 basic patch), while the Orc4 insertion helix (IH) inserts into the major groove and underlies much of the sequence specificity in budding yeast (tye2023theoriginrecognition pages 2-4).

A major 2024 advance is the genome-scale dissection of ORC DNA-binding determinants by mapping 38 designed ORC mutants. This work shows that origin binding can depend on distinct Orc1 disordered basic patches and on Orc4 IH, and that origins can be partitioned into two dominant motif variants with different binding requirements (chappleboim2024orderedanddisordered pages 1-1). Specifically, replication origins contain a 17 bp motif, and origin binding in vivo can require Orc1-BP4 and Orc4-IH for one motif class, while another class can use Orc1-BP3 in place of Orc4-IH (chappleboim2024orderedanddisordered pages 1-1).

3.3 Pre-RC assembly and helicase loading (interactions: Cdc6, Cdt1–Mcm2–7)

In early G1, ORC (including Orc1) recruits Cdc6, then Cdt1–MCM2–7, loading MCM one hexamer at a time to form a head-to-head MCM double hexamer (tye2023theoriginrecognition pages 1-2). Structural and mechanistic work indicates that ORC bends DNA at origin elements in a manner that helps align and insert DNA into the MCM ring during formation of helicase-loading intermediates (tye2023theoriginrecognition pages 2-4, schmidt2022amechanismof pages 1-2). The ORC·DNA·Cdc6 ring architecture and its regulation by conformational switches (including an autoinhibited state involving Orc6) are described by cryo-EM structures at ~2.5–2.7 Å resolution (schmidt2022amechanismof pages 1-2).

4) Orc1 roles in chromatin biology and transcriptional silencing (BAH domain)

4.1 Orc1 BAH domain binds nucleosomes (substrate: nucleosome core particle / histone tails)

A central experimentally supported non-enzymatic function of Orc1 is nucleosome binding through the BAH domain. A structural study determined the Orc1 BAH–nucleosome complex at 3.3 Å and reported that Orc1 BAH forms extensive contacts with core histones, burying ~1590 Å² of surface (ioannes2019structureandfunction pages 1-2). Importantly, Orc1 differs from its paralog Sir3 in that Orc1 BAH does not strongly discriminate between acetylated and non-acetylated H4K16, consistent with a chromatin-binding role across eu- and heterochromatin (ioannes2019structureandfunction pages 1-2). Sequence similarity between Orc1 and Sir3 BAH domains is reported as 48% identity / 67% similarity (ioannes2019structureandfunction pages 1-2).

Recent genome-wide functional mapping provides in vivo support for the modularity of Orc1 targeting: Orc1 lacking the BAH domain is lost from silencing-associated sites but remains bound to replication origins, whereas an isolated Orc1 N-terminal tail (~375 aa; containing BAH) is sufficient for strong binding at silencing-associated sites (chappleboim2024orderedanddisordered pages 5-5). A peer-reviewed 2024 study further states that at silencing-associated loci lacking the canonical origin motif, ORC binding and activity are “fully explained” by the BAH domain (chappleboim2024orderedanddisordered pages 1-1).

4.2 Sir1 recruitment and HM silencing

At the silent mating-type loci, Orc1’s BAH domain plays a mechanistic role in nucleating silenced chromatin. Orc1 BAH binds at DNA silencer elements and recruits Sir1, which then helps recruit the Sir2/Sir3/Sir4 silencing machinery (ioannes2019structureandfunction pages 1-2). Structure-guided mutagenesis in a classic EMBO Journal study identified a specific helical insertion within the Orc1 BAH domain that confers Sir1-binding specificity; mutants disrupting this region phenocopied sir1Δ, producing strong defects in silencing readouts (colony color and mating-pheromone “shmooing”) with quantitative changes (e.g., ~80% resistance to α-factor and ~14–20% shmooing versus >90% shmooing in controls) (zhang2002structureandfunction pages 2-3).

4.3 Telomeres and silent chromatin architecture beyond silencers

ORC’s role in silencing extends beyond a single silencer-bound nucleation site. ChIP-based evidence indicates ORC can associate throughout the internal regions of HMR, including sequences lacking canonical ACS, and that this association depends on Sir proteins and silent chromatin context (ozaydın2010expandedrolesof pages 1-2). Orc1’s BAH domain and Orc1–Sir1 interaction are proposed contributors to this broader association and to silent chromatin architecture (ozaydın2010expandedrolesof pages 12-13, ozaydın2010expandedrolesof pages 1-2). Telomeric silencing is reported to depend on Orc1’s BAH domain and on N-terminal acetylation of Orc1 by NatA-Ard, linking a post-translational modification to silencing function (ioannes2019structureandfunction pages 1-2).

4.4 rDNA border integrity (meiosis)

In addition to replication and silencing, Orc1 BAH–nucleosome interactions contribute to genome stability at rDNA borders during meiosis; reduced Orc1-BAH affinity is associated with increased double-strand breaks, implying that direct nucleosome binding is required for this protective function (ioannes2019structureandfunction pages 1-2). In one source, the rDNA locus is described as a tandem array of ~100–200 copies of a 9.1 kb repeat, with ~20% active origins (geissenhoner2004theroleof pages 25-28).

5) Cellular localization and cell-cycle regulation

Chromatin association across the cell cycle and G1-restricted licensing

Multiple lines of evidence support that ORC is a chromatin-bound initiator that can remain associated with origin DNA across the cell cycle. One source states ORC binds ACS sites distributed genome-wide and “remains bound throughout the cell cycle,” with Orc1 ATP binding required for DNA binding (geissenhoner2004theroleof pages 25-28). Functionally, the licensing reaction (MCM loading) is concentrated in early G1; after G1, CDK-dependent phosphorylation inhibits re-licensing to prevent rereplication (tye2023theoriginrecognition pages 1-2).

Recent regulatory mechanisms (2024)

Recent work emphasizes that regulation of licensing involves intrinsically disordered regulatory elements within ORC subunits (including but not limited to Orc1). A 2024 Nature Communications study identifies an Orc2 N-terminal IDR segment (residues 176–200) whose mutation impairs ATP hydrolysis in later helicase-loading transitions and blocks formation of downstream intermediates (wu2024replicationlicensingregulated pages 1-2). A 2024 preprint proposes that CDK phosphorylation of an Orc2 IDR blocks formation of a key MCM–ORC intermediate required for second-hexamer loading, shaping origin architecture and explaining how certain origins can partially escape CDK inhibition (lim2024cellcycleregulation pages 1-2).

6) Recent developments and latest research (priority 2023–2024)

6.1 High-resolution structural era integrated with genome-wide mutant mapping

A prominent 2023 theme is the integration of high-resolution cryo-EM structures with genetic and biochemical reconstitution, enabling explicit structural hypotheses about origin selection and helicase loading (tye2023theoriginrecognition pages 2-4, tye2023theoriginrecognition pages 1-2). In 2024, this structural understanding is complemented by genome-wide mutant binding maps demonstrating that ORC’s DNA-binding logic is modular and context-dependent: disordered Orc1 basic patches contribute to motif-specific origin binding, while Orc1 BAH explains binding at non-origin silencing-associated loci (chappleboim2024orderedanddisordered pages 1-1).

6.2 Distinguishing replication-origin binding from silencing-associated binding

A clear recent advance is the experimental separation of Orc1’s origin-binding determinants from its silencing-locus determinants. In vivo, loss of BAH abolishes binding at silencing-associated loci but not at origins, while origin binding can be strongly reduced by deletion of Orc1-BP4 (which is also reported essential for growth) (chappleboim2024orderedanddisordered pages 5-5). This supports the modern view that ORC uses different interfaces for “replication origin” versus “silent chromatin” genomic occupancy (chappleboim2024orderedanddisordered pages 5-5, chappleboim2024orderedanddisordered pages 1-1).

7) Current applications and real-world implementations

In vitro reconstitution of replication initiation steps: Recent reviews emphasize that the yeast replisome assembly process (including ORC-dependent licensing) has been reconstituted in vitro using purified yeast proteins, enabling controlled mechanistic dissection and direct testing of mutants and regulatory signals (tye2023theoriginrecognition pages 1-2).
Genome-wide ORC binding logic as an engineering/interpretation tool: The 2024 ORC mutant-binding atlas provides a blueprint for predicting which origin classes depend on specific DNA-contacting modules (e.g., Orc1-BP4 vs Orc4-IH) and which chromatin loci depend on Orc1 BAH, supporting rational perturbations of origin usage and silent-chromatin nucleation in yeast systems biology and synthetic biology workflows (chappleboim2024orderedanddisordered pages 1-1, chappleboim2024orderedanddisordered pages 5-5).
Replication stress and genome stability frameworks: Disruption of origin recognition modules (e.g., Orc4 IH deletion) is associated with prolonged G2 and Rad53 phosphorylation (checkpoint activation), tying ORC-mediated origin selection to genome integrity; yeast ORC remains a key model for understanding replication stress mechanisms relevant to disease biology (tye2023theoriginrecognition pages 2-4, tye2023theoriginrecognition pages 1-2).

8) Expert synthesis and authoritative perspectives

A recent review explicitly contrasts yeast and human origin selection strategies: yeast uses sequence-specific ORC recognition at ARSs, whereas human ORC is more strongly guided by chromatin landscape, and pre-RCs can form distant from ORC binding sites (tye2023theoriginrecognition pages 1-2). This comparative framing supports an expert consensus that budding yeast ORC (and Orc1) remains the clearest mechanistic paradigm for origin licensing because origin sequences are compact and experimentally tractable, while also highlighting which features (e.g., Orc4 insertion helix) are lineage-specific and thus should not be naively extrapolated (tye2023theoriginrecognition pages 2-4, tye2023theoriginrecognition pages 1-2).

9) Key statistics and data points (from cited studies)

ORC complex size: ~400 kDa (parker2017mechanismsandregulation pages 4-6).
Origin motif length: ACS ~17 bp; essential core often described as 11 bp (tye2023theoriginrecognition pages 2-4).
Number of origins/ARSs: >400 ARSs, 249 canonical-feature ARSs (tye2023theoriginrecognition pages 2-4).
Cryo-EM resolution (ORC–DNA): 3.0 Å (ORC bound to 72 bp ARS305 DNA) (tye2023theoriginrecognition pages 2-4).
Cryo-EM resolution (ORC·DNA·Cdc6 intermediates): ~2.5–2.7 Å (schmidt2022amechanismof pages 1-2).
Orc1 BAH–nucleosome structure: 3.3 Å; ~1590 Å² buried interface (ioannes2019structureandfunction pages 1-2).
Orc1/Sir3 BAH similarity: 48% identity; 67% similarity (ioannes2019structureandfunction pages 1-2).
rDNA locus: ~100–200 tandem repeats of 9.1 kb; ~20% active origins in one cited description (geissenhoner2004theroleof pages 25-28).
Quantitative silencing phenotypes for Orc1 BAH mutants: Orc1 “H insertion” mutant (orc1m1) yields ~80% α-factor resistance and ~14–20% shmooing, similar to sir1Δ, compared with >90% shmooing for wild type-like controls (zhang2002structureandfunction pages 2-3).

10) Summary functional annotation (evidence-backed)

Orc1 (ORC1/YML065W; UniProt P54784) is a chromatin-associated initiator protein and the largest subunit of ORC that (i) supports ATP-dependent, sequence-specific origin recognition and pre-RC assembly through AAA+ initiator mechanisms, DNA bending, and regulated ATPase-site configurations that coordinate recruitment/loading of Cdc6 and MCM2–7 (tye2023theoriginrecognition pages 2-4, schmidt2022amechanismof pages 1-2, parker2017mechanismsandregulation pages 4-6), and (ii) mediates chromatin/nucleosome interactions and transcriptional silencing via its N-terminal BAH domain, which binds nucleosomes, recruits Sir1 at HM silencers, contributes to telomeric silencing (including via NatA-mediated acetylation), and supports rDNA border integrity during meiosis (ioannes2019structureandfunction pages 1-2, zhang2002structureandfunction pages 2-3, chappleboim2024orderedanddisordered pages 5-5).

Evidence limitations (explicitly noted)

Within the retrieved evidence set, Orc1’s ATPase function is described qualitatively and structurally, but explicit kinetic parameters (e.g., kcat/Km for Orc1 ATP hydrolysis) were not captured in the available excerpts; answering that precisely would require targeted retrieval of dedicated biochemical enzymology papers beyond the current set (parker2017mechanismsandregulation pages 4-6, schmidt2022amechanismof pages 1-2).

Embedded summary table

Functional aspect	Key mechanistic details	Quantitative/data points	Key recent sources (date; URL)
Origin licensing	Orc1 is the largest ORC subunit in the six-subunit origin recognition complex that binds budding-yeast replication origins in an ATP-dependent manner. In early G1, ORC with Cdc6 recruits Cdt1-Mcm2-7 and loads a head-to-head MCM double hexamer to form the pre-replicative complex; cryo-EM work shows ORC bends origin DNA and positions it for helicase loading. Orc1 contributes DNA-contacting/basic elements within the ORC-DNA interface and participates in the ATPase architecture that coordinates loading. (tye2023theoriginrecognition pages 1-2, schmidt2022amechanismof pages 1-2, tye2023theoriginrecognition pages 2-4)	ARS consensus sequence (ACS) is 17 bp; essential core often described as 11 bp (WTTTATRTTTW). >400 ARSs identified genome-wide, with 249 canonical features noted in the review. Yeast ORC bound to 72 bp of ARS305 (ACS+B1) solved at 3.0 Å; ORC-Cdc6-DNA intermediates reported at ~2.5-2.7 Å. (tye2023theoriginrecognition pages 1-2, tye2023theoriginrecognition pages 2-4, schmidt2022amechanismof pages 1-2)	Tye & Zhai, 2023, Biology (Dec 2023): https://doi.org/10.3390/biology13010013 ; Feng et al., 2021, Nat Commun (Jun 2021): https://doi.org/10.1038/s41467-021-24199-1 ; Schmidt et al., 2022, Nat Commun (Feb 2022): https://doi.org/10.1038/s41467-022-28695-w
ATPase / DNA binding	Orc1 belongs to the AAA+ ATPase-containing ORC core; reviews identify Orc1 as the only ORC subunit experimentally demonstrated to have ATPase activity. The Orc1-Orc4 and Cdc6-Orc1 composite ATPase sites are central to origin licensing, and ATP binding is required for origin-specific DNA binding and MCM loading. DNA recognition combines base-specific and backbone contacts: Orc1 basic patches engage the DNA minor groove, while Orc4 insertion helix contacts the major groove. Genome-wide mutagenesis shows different Orc1 basic patches contribute differentially across origin classes. (parker2017mechanismsandregulation pages 4-6, schmidt2022amechanismof pages 1-2, chappleboim2024orderedanddisordered pages 1-1, tye2023theoriginrecognition pages 2-4)	ORC is ~400 kDa. Cryo-EM structural work used truncated Orc1 residues 355-914 for some ORC-DNA analyses. Orc1-BP4 modeled at aa 356-373; MD used a 20-nt ARS segment. Genome-wide study tested 38 designed ORC mutants and analyzed top 150 bound origins within 300-bp windows. (parker2017mechanismsandregulation pages 4-6, chappleboim2024orderedanddisordered pages 1-1, chappleboim2024orderedanddisordered pages 3-4)	Chappleboim et al., 2024, Nucleic Acids Res (Apr 2024): https://doi.org/10.1093/nar/gkae249 ; Tye & Zhai, 2023, Biology (Dec 2023): https://doi.org/10.3390/biology13010013 ; Parker et al., 2017, Crit Rev Biochem Mol Biol (Jan 2017): https://doi.org/10.1080/10409238.2016.1274717
Chromatin / BAH nucleosome binding	The N-terminal BAH domain of Orc1 is a chromatin-binding module distinct from the AAA+ region. Structural work shows Orc1 BAH binds the nucleosome core directly, contacting histones H2A/H2B/H3/H4 and helping target ORC to a class of origins and chromatin sites. Unlike Sir3, Orc1 BAH does not strongly discriminate H4K16 acetylation state, consistent with function in both eu- and heterochromatin. Recent genome-wide work shows BAH is dispensable for binding at canonical origins but essential for binding/activity at silencing-associated loci lacking the canonical motif. (ioannes2019structureandfunction pages 1-2, chappleboim2024orderedanddisordereda pages 3-5, chappleboim2024orderedanddisordered pages 12-12, tye2023theoriginrecognition pages 6-8)	Orc1 is 914 aa. Orc1 BAH-nucleosome structure solved at 3.3 Å and buries ~1590 Å² of surface. Orc1/Sir3 BAH similarity reported as 48% identity and 67% similarity. An isolated ~375-aa Orc1 N-terminal tail containing BAH retained strong binding to silencing-associated loci. (ioannes2019structureandfunction pages 1-2, chappleboim2024orderedanddisordereda pages 3-5, chacin2023establishmentandfunction pages 19-22)	Chappleboim et al., 2024, Nucleic Acids Res (Apr 2024): https://doi.org/10.1093/nar/gkae249 ; De Ioannes et al., 2019, Nat Commun (Jul 2019): https://doi.org/10.1038/s41467-019-10609-y ; Tye & Zhai, 2023, Biology (Dec 2023): https://doi.org/10.3390/biology13010013
Silencing / heterochromatin	Beyond replication, Orc1 has a well-established silencing role through its BAH domain. At HM silencers, Orc1 BAH helps recruit Sir1 and nucleate SIR-mediated heterochromatin. Structural/functional studies also support Orc1 roles at telomeres and in protecting rDNA borders during meiosis through direct chromatin interactions. Recent in vivo mapping indicates silencing-associated ORC sites lacking the replication motif are explained largely by BAH-mediated targeting. (ioannes2019structureandfunction pages 1-2, chappleboim2024orderedanddisordereda pages 3-5, chappleboim2024orderedanddisordered pages 12-12)	HM silencing-associated sites can retain Orc1 N-tail/BAH binding even when canonical origin-like recognition is absent. rDNA arrays are reported as ~100-200 copies of a 9.1 kb repeat, with only ~20% of repeats functioning as active origins in one cited source. (chappleboim2024orderedanddisordereda pages 3-5, geissenhoner2004theroleof pages 25-28)	Dhillon & Kamakaka, 2024, Epigenetics & Chromatin (Sep 2024): https://doi.org/10.1186/s13072-024-00553-7 ; De Ioannes et al., 2019, Nat Commun (Jul 2019): https://doi.org/10.1038/s41467-019-10609-y ; Hou et al., 2005, PNAS (Jun 2005): https://doi.org/10.1073/pnas.0503525102 ; Zhang et al., 2002, EMBO J (Sep 2002): https://doi.org/10.1093/emboj/cdf468
Regulation	ORC activity is cell-cycle regulated to permit licensing only in G1. CDK-dependent phosphorylation inhibits re-licensing after G1. Recent work highlights regulatory intrinsically disordered regions (IDRs): Orc2 contains a short linear motif/IDR segment needed for MO intermediate formation and second-hexamer loading, and CDK phosphorylation of this IDR blocks MO and double-hexamer assembly. Separate structural work identified an autoinhibitory ORC-Cdc6-DNA state in which Orc6 blocks productive MCM docking. These studies place Orc1 within a broader ORC regulatory network controlling helicase loading and preventing rereplication. (tye2023theoriginrecognition pages 1-2, lim2024cellcycleregulation pages 1-2, wu2024replicationlicensingregulated pages 1-2, schmidt2022amechanismof pages 1-2)	Orc2 IDR segment 176-200, with key residue I194, is essential; Orc2 CDK phosphosites include S206, T217, T219. Origins with two high-affinity ORC sites can bypass the MO-dependent pathway and partially escape CDK inhibition. Orc4 insertion helix is a 19-aa insertion; deleting it yields viable cells with prolonged G2 and Rad53 phosphorylation. (lim2024cellcycleregulation pages 1-2, wu2024replicationlicensingregulated pages 1-2, tye2023theoriginrecognition pages 2-4)	Wu et al., 2024, Nat Commun (Sep 2024): https://doi.org/10.1038/s41467-024-52408-0 ; Lim et al., 2024, bioRxiv (Jan 2024): https://doi.org/10.1101/2024.01.10.575016 ; Schmidt et al., 2022, Nat Commun (Feb 2022): https://doi.org/10.1038/s41467-022-28695-w ; Tye & Zhai, 2023, Biology (Dec 2023): https://doi.org/10.3390/biology13010013

Table: This table summarizes the main experimentally supported functions of Saccharomyces cerevisiae Orc1, separating its replication-initiation, ATPase/DNA-binding, chromatin-binding, silencing, and regulatory roles. It emphasizes recent 2023-2024 studies while retaining seminal mechanistic papers for context.

References

(ioannes2019structureandfunction pages 1-2): Pablo De Ioannes, Victor A. Leon, Zheng Kuang, Miao Wang, Jef D. Boeke, Andreas Hochwagen, and Karim-Jean Armache. Structure and function of the orc1 bah-nucleosome complex. Nature Communications, Jul 2019. URL: https://doi.org/10.1038/s41467-019-10609-y, doi:10.1038/s41467-019-10609-y. This article has 52 citations and is from a highest quality peer-reviewed journal.
(chappleboim2024orderedanddisordered pages 1-1): Michal Chappleboim, Segev Naveh-Tassa, Miri Carmi, Yaakov Levy, and Naama Barkai. Ordered and disordered regions of the origin recognition complex direct differential in vivo binding at distinct motif sequences. Nucleic Acids Research, 52:5720-5731, Apr 2024. URL: https://doi.org/10.1093/nar/gkae249, doi:10.1093/nar/gkae249. This article has 7 citations and is from a highest quality peer-reviewed journal.
(chacin2023establishmentandfunction pages 19-22): Erika Chacin. Establishment and function of nucleosome organization at eukaryotic chromosome replication origins. Dissertation, Jan 2023. URL: https://doi.org/10.5282/edoc.33330, doi:10.5282/edoc.33330. This article has 0 citations.
(tye2023theoriginrecognition pages 1-2): Bik-Kwoon Tye and Yuanliang Zhai. The origin recognition complex: from origin selection to replication licensing in yeast and humans. Biology, 13:13, Dec 2023. URL: https://doi.org/10.3390/biology13010013, doi:10.3390/biology13010013. This article has 10 citations.
(parker2017mechanismsandregulation pages 4-6): Matthew W. Parker, Michael R. Botchan, and James M. Berger. Mechanisms and regulation of dna replication initiation in eukaryotes. Critical Reviews in Biochemistry and Molecular Biology, 52:107-144, Jan 2017. URL: https://doi.org/10.1080/10409238.2016.1274717, doi:10.1080/10409238.2016.1274717. This article has 244 citations and is from a peer-reviewed journal.
(tye2023theoriginrecognition pages 2-4): Bik-Kwoon Tye and Yuanliang Zhai. The origin recognition complex: from origin selection to replication licensing in yeast and humans. Biology, 13:13, Dec 2023. URL: https://doi.org/10.3390/biology13010013, doi:10.3390/biology13010013. This article has 10 citations.
(chappleboim2024orderedanddisordered pages 5-5): Michal Chappleboim, Segev Naveh-Tassa, Miri Carmi, Yaakov Levy, and Naama Barkai. Ordered and disordered regions of the origin recognition complex direct differential in vivo binding at distinct motif sequences. Nucleic Acids Research, 52:5720-5731, Apr 2024. URL: https://doi.org/10.1093/nar/gkae249, doi:10.1093/nar/gkae249. This article has 7 citations and is from a highest quality peer-reviewed journal.
(geissenhoner2004theroleof pages 25-28): Antje Geißenhöner. The role of the n-terminal acetyltransferase nata in transcriptional silencing in saccharomyces cerevisiae. ArXiv, Oct 2004. URL: https://doi.org/10.18452/15123, doi:10.18452/15123. This article has 0 citations.
(schmidt2022amechanismof pages 1-2): Jan Marten Schmidt, Ran Yang, Ashish Kumar, Olivia Hunker, Jan Seebacher, and Franziska Bleichert. A mechanism of origin licensing control through autoinhibition of s. cerevisiae orc·dna·cdc6. Nature Communications, Feb 2022. URL: https://doi.org/10.1038/s41467-022-28695-w, doi:10.1038/s41467-022-28695-w. This article has 23 citations and is from a highest quality peer-reviewed journal.
(zhang2002structureandfunction pages 2-3): Zhiguo Zhang, M. Hayashi, O. Merkel, B. Stillman, and R. Xu. Structure and function of the bah‐containing domain of orc1p in epigenetic silencing. The EMBO Journal, 21:4600-4611, Sep 2002. URL: https://doi.org/10.1093/emboj/cdf468, doi:10.1093/emboj/cdf468. This article has 143 citations.
(ozaydın2010expandedrolesof pages 1-2): Bilge Özaydın and Jasper Rine. Expanded roles of the origin recognition complex in the architecture and function of silenced chromatin in saccharomyces cerevisiae. Feb 2010. URL: https://doi.org/10.1128/mcb.00614-09, doi:10.1128/mcb.00614-09. This article has 29 citations and is from a domain leading peer-reviewed journal.
(ozaydın2010expandedrolesof pages 12-13): Bilge Özaydın and Jasper Rine. Expanded roles of the origin recognition complex in the architecture and function of silenced chromatin in saccharomyces cerevisiae. Feb 2010. URL: https://doi.org/10.1128/mcb.00614-09, doi:10.1128/mcb.00614-09. This article has 29 citations and is from a domain leading peer-reviewed journal.
(wu2024replicationlicensingregulated pages 1-2): Yue Wu, Qiongdan Zhang, Yuhan Lin, Wai Hei Lam, and Yuanliang Zhai. Replication licensing regulated by a short linear motif within an intrinsically disordered region of origin recognition complex. Nature Communications, Sep 2024. URL: https://doi.org/10.1038/s41467-024-52408-0, doi:10.1038/s41467-024-52408-0. This article has 5 citations and is from a highest quality peer-reviewed journal.
(lim2024cellcycleregulation pages 1-2): Chew Theng Lim, Thomas C.R. Miller, Kang Wei Tan, Saurabh Talele, Anne Early, Philip East, Humberto Sánchez, Nynke H. Dekker, Alessandro Costa, and John F.X. Diffley. Cell cycle regulation has shaped budding yeast replication origin structure and function. bioRxiv, Jan 2024. URL: https://doi.org/10.1101/2024.01.10.575016, doi:10.1101/2024.01.10.575016. This article has 9 citations.
(chappleboim2024orderedanddisordered pages 3-4): Michal Chappleboim, Segev Naveh-Tassa, Miri Carmi, Yaakov Levy, and Naama Barkai. Ordered and disordered regions of the origin recognition complex direct differential in vivo binding at distinct motif sequences. Nucleic Acids Research, 52:5720-5731, Apr 2024. URL: https://doi.org/10.1093/nar/gkae249, doi:10.1093/nar/gkae249. This article has 7 citations and is from a highest quality peer-reviewed journal.
(chappleboim2024orderedanddisordereda pages 3-5): Michal Chappleboim, Segev Naveh-Tassa, Miri Carmi, Yaakov Levy, and Naama Barkai. Ordered and disordered regions of the origin recognition complex (orc) combine to direct in-vivo binding at symmetric and non-symmetric motif sequences. bioRxiv, Jan 2024. URL: https://doi.org/10.1101/2024.01.27.577596, doi:10.1101/2024.01.27.577596. This article has 0 citations.
(chappleboim2024orderedanddisordered pages 12-12): Michal Chappleboim, Segev Naveh-Tassa, Miri Carmi, Yaakov Levy, and Naama Barkai. Ordered and disordered regions of the origin recognition complex direct differential in vivo binding at distinct motif sequences. Nucleic Acids Research, 52:5720-5731, Apr 2024. URL: https://doi.org/10.1093/nar/gkae249, doi:10.1093/nar/gkae249. This article has 7 citations and is from a highest quality peer-reviewed journal.
(tye2023theoriginrecognition pages 6-8): Bik-Kwoon Tye and Yuanliang Zhai. The origin recognition complex: from origin selection to replication licensing in yeast and humans. Biology, 13:13, Dec 2023. URL: https://doi.org/10.3390/biology13010013, doi:10.3390/biology13010013. This article has 10 citations.

Artifacts

Edison artifact artifact-00

Citations

tye2023theoriginrecognition pages 1-2
tye2023theoriginrecognition pages 2-4
parker2017mechanismsandregulation pages 4-6
geissenhoner2004theroleof pages 25-28
schmidt2022amechanismof pages 1-2
chappleboim2024orderedanddisordered pages 1-1
ioannes2019structureandfunction pages 1-2
chappleboim2024orderedanddisordered pages 5-5
zhang2002structureandfunction pages 2-3
ozaydın2010expandedrolesof pages 1-2
wu2024replicationlicensingregulated pages 1-2
lim2024cellcycleregulation pages 1-2
chacin2023establishmentandfunction pages 19-22
ozaydın2010expandedrolesof pages 12-13
chappleboim2024orderedanddisordered pages 3-4
chappleboim2024orderedanddisordereda pages 3-5
chappleboim2024orderedanddisordered pages 12-12
tye2023theoriginrecognition pages 6-8
https://doi.org/10.3390/biology13010013
https://doi.org/10.1038/s41467-021-24199-1
https://doi.org/10.1038/s41467-022-28695-w
https://doi.org/10.1093/nar/gkae249
https://doi.org/10.1080/10409238.2016.1274717
https://doi.org/10.1038/s41467-019-10609-y
https://doi.org/10.1186/s13072-024-00553-7
https://doi.org/10.1073/pnas.0503525102
https://doi.org/10.1093/emboj/cdf468
https://doi.org/10.1038/s41467-024-52408-0
https://doi.org/10.1101/2024.01.10.575016
https://doi.org/10.1038/s41467-019-10609-y,
https://doi.org/10.1093/nar/gkae249,
https://doi.org/10.5282/edoc.33330,
https://doi.org/10.3390/biology13010013,
https://doi.org/10.1080/10409238.2016.1274717,
https://doi.org/10.18452/15123,
https://doi.org/10.1038/s41467-022-28695-w,
https://doi.org/10.1093/emboj/cdf468,
https://doi.org/10.1128/mcb.00614-09,
https://doi.org/10.1038/s41467-024-52408-0,
https://doi.org/10.1101/2024.01.10.575016,
https://doi.org/10.1101/2024.01.27.577596,

📄 View Raw YAML

id: P54784
gene_symbol: ORC1
aliases:
  - YML065W
product_type: PROTEIN
status: INITIALIZED
taxon:
  id: NCBITaxon:559292
  label: Saccharomyces cerevisiae
description: 'Origin recognition complex subunit 1 (ORC1) is the 120 kDa catalytic subunit of the ORC complex, essential for DNA replication initiation and mating-type transcriptional silencing. ORC1 recognizes and binds ARS consensus sequences at replication origins, recruits MCM2-7 loading factors during G1, and interacts with SIR proteins to establish heterochromatin at silent mating loci. The protein contains an N-terminal BAH (bromo-adjacent homology) domain for nucleosome binding and a C-terminal AAA+ ATPase domain for ATP-dependent chromatin remodeling.'
existing_annotations:
- term:
    id: GO:0006270
    label: DNA replication initiation
  evidence_type: IBA
  original_reference_id: GO_REF:0000033
  review:
    summary: 'IBA annotation well-supported by experimental evidence and phylogenetic orthology. ORC1 is essential for G1/S loading of MCM complexes and formation of the pre-replicative complex.'
    action: ACCEPT
    reason: 'Core function. Multiple experimental studies (IDA, IMP, NAS) confirm ORC1s role in DNA replication initiation through pre-replicative complex assembly and MCM loading.'
    additional_reference_ids:
      - file:yeast/ORC1/ORC1-deep-research-falcon.md
    supported_by:
      - reference_id: PMID:16824194
        supporting_text: 'Reconstitution of Saccharomyces cerevisiae prereplicative complex assembly in vitro'
      - reference_id: file:yeast/ORC1/ORC1-deep-research-falcon.md
        supporting_text: |-
          In early G1, ORC (including Orc1) recruits **Cdc6**, then **Cdt1–MCM2–7**, loading MCM one hexamer at a time to form a head-to-head MCM double hexamer
- term:
    id: GO:0003688
    label: DNA replication origin binding
  evidence_type: IBA
  original_reference_id: GO_REF:0000033
  review:
    summary: 'IBA annotation reflects the fundamental mechanism by which ORC1 initiates DNA replication through recognition of ARS consensus sequences.'
    action: ACCEPT
    reason: 'Core molecular function. ORC1 specifically binds ARS consensus sequences (ACS) at replication origins. This is well-established experimentally (IDA evidence PMID:16824194).'
    additional_reference_ids:
      - file:yeast/ORC1/ORC1-deep-research-falcon.md
    supported_by:
      - reference_id: PMID:16824194
        supporting_text: 'Reconstitution of Saccharomyces cerevisiae prereplicative complex assembly in vitro'
      - reference_id: file:yeast/ORC1/ORC1-deep-research-falcon.md
        supporting_text: |-
          recognizes a replication-origin DNA consensus (ARS consensus sequence, ACS) and acts as the platform that seeds helicase loading and replication initiation
- term:
    id: GO:0033314
    label: mitotic DNA replication checkpoint signaling
  evidence_type: IBA
  original_reference_id: GO_REF:0000033
  review:
    summary: 'IBA annotation inferred from phylogenetic orthology. ORC1 is involved in checkpoint responses to aberrant replication.'
    action: KEEP_AS_NON_CORE
    reason: 'While ORC1 is involved in replication checkpoint signaling, this is peripheral to its primary role in replication initiation. The checkpoint function is largely indirect through replication failure surveillance. IBA annotations are conservative and this may represent a non-essential secondary function.'
    supported_by:
      - reference_id: PMID:16716188
        supporting_text: 'Cell cycle execution point analysis of ORC function and characterization of the checkpoint response to ORC inactivation in Saccharomyces cerevisiae'
- term:
    id: GO:0005664
    label: nuclear origin of replication recognition complex
  evidence_type: IBA
  original_reference_id: GO_REF:0000033
  review:
    summary: 'IBA annotation correctly identifies ORC1 as part of the ORC complex, a multi-subunit assembly.'
    action: ACCEPT
    reason: 'Accurate. ORC1 is a core structural component of the ORC complex. Experimentally validated (IDA, IMP evidence).'
    additional_reference_ids:
      - file:yeast/ORC1/ORC1-deep-research-falcon.md
    supported_by:
      - reference_id: PMID:9372948
        supporting_text: 'Architecture of the yeast origin recognition complex bound to origins of DNA replication'
      - reference_id: file:yeast/ORC1/ORC1-deep-research-falcon.md
        supporting_text: |-
          ORC is a large (~400 kDa) heterohexamer (Orc1–6) that recognizes a replication-origin DNA consensus
- term:
    id: GO:0000166
    label: nucleotide binding
  evidence_type: IEA
  original_reference_id: GO_REF:0000043
  review:
    summary: 'IEA annotation based on UniProtKB keyword mapping. ORC1 contains AAA+ ATPase domain with ATP binding capability.'
    action: KEEP_AS_NON_CORE
    reason: 'Mechanically correct but overly generic. ORC1 contains multiple ATP binding sites (documented in UniProt features), but the more specific ATP binding annotation (GO:0005524) is more informative. Nucleotide binding as a general term lacks specificity for ORC1s characterized ATP hydrolysis activity.'
    additional_reference_ids:
      - file:yeast/ORC1/ORC1-deep-research-falcon.md
    supported_by:
      - reference_id: file:yeast/ORC1/ORC1-deep-research-falcon.md
        supporting_text: |-
          ATP binding by Orc1 is required for ORC DNA binding
- term:
    id: GO:0003677
    label: DNA binding
  evidence_type: IEA
  original_reference_id: GO_REF:0000043
  review:
    summary: 'IEA annotation based on UniProtKB keyword mapping reflects ORC1s well-documented ARS-binding capability.'
    action: KEEP_AS_NON_CORE
    reason: 'Technically accurate but too generic. GO:0003688 (DNA replication origin binding) is more specific and informative. General DNA binding term obscures the specialized function of recognizing specific ARS sequences.'
    additional_reference_ids:
      - file:yeast/ORC1/ORC1-deep-research-falcon.md
    supported_by:
      - reference_id: PMID:16824194
        supporting_text: 'Reconstitution of Saccharomyces cerevisiae prereplicative complex assembly in vitro'
      - reference_id: file:yeast/ORC1/ORC1-deep-research-falcon.md
        supporting_text: |-
          Orc1 and Orc2 contribute **minor-groove interactions** (e.g., Orc1 basic patch)
- term:
    id: GO:0003682
    label: chromatin binding
  evidence_type: IEA
  original_reference_id: GO_REF:0000002
  review:
    summary: 'IEA annotation inferred from InterPro BAH domain (IPR001025). ORC1 contains a BAH domain for nucleosome interaction.'
    action: ACCEPT
    reason: 'Mechanically correct - ORC1 has a BAH domain and binds chromatin/nucleosomes. The more specific nucleosome binding term (GO:0031491) is also annotated with IDA evidence, so this broader term is acceptable as a complementary annotation.'
    additional_reference_ids:
      - file:yeast/ORC1/ORC1-deep-research-falcon.md
    supported_by:
      - reference_id: PMID:31263106
        supporting_text: 'Structure and function of the Orc1 BAH-nucleosome complex'
      - reference_id: file:yeast/ORC1/ORC1-deep-research-falcon.md
        supporting_text: |-
          The N-terminal BAH domain of Orc1 is a chromatin-binding module distinct from the AAA+ region
- term:
    id: GO:0003688
    label: DNA replication origin binding
  evidence_type: IEA
  original_reference_id: GO_REF:0000117
  review:
    summary: 'IEA annotation from ARBA machine learning model correctly identifies ORC1s origin binding function.'
    action: ACCEPT
    reason: 'Well-supported. This duplicates the IBA and IDA annotations for the same term but with different evidence code. Core molecular function. Experimental validation exists (IDA PMID:16824194).'
    supported_by:
      - reference_id: PMID:16824194
        supporting_text: 'Reconstitution of Saccharomyces cerevisiae prereplicative complex assembly in vitro'
- term:
    id: GO:0005524
    label: ATP binding
  evidence_type: IEA
  original_reference_id: GO_REF:0000120
  review:
    summary: 'IEA annotation from combined automated methods identifies ATP binding in AAA+ domain.'
    action: ACCEPT
    reason: 'Mechanically correct - ORC1 has well-documented ATP binding sites (see UniProt features at positions 435, 479-487, 567, 600, 704, 726-733). While ATP hydrolysis activity is also annotated, ATP binding is a distinct and essential molecular function.'
    additional_reference_ids:
      - file:yeast/ORC1/ORC1-deep-research-falcon.md
    supported_by:
      - reference_id: file:yeast/ORC1/ORC1-deep-research-falcon.md
        supporting_text: |-
          ATP binding by Orc1 is required for ORC DNA binding
- term:
    id: GO:0005634
    label: nucleus
  evidence_type: IEA
  original_reference_id: GO_REF:0000044
  review:
    summary: 'IEA annotation from UniProtKB subcellular location vocabulary correctly identifies nuclear localization.'
    action: KEEP_AS_NON_CORE
    reason: 'Correct but non-specific cellular component term. ORC1 is nuclear, but this is required for all its functions. Experimental evidence (EXP, IDA) for nucleoplasm and nucleus localization available.'
    supported_by:
      - reference_id: PMID:11168584
        supporting_text: 'Interactions between Mcm10p and other replication factors are required for proper initiation and elongation of chromosomal DNA replication in Saccharomyces cerevisiae'
- term:
    id: GO:0005694
    label: chromosome
  evidence_type: IEA
  original_reference_id: GO_REF:0000117
  review:
    summary: 'IEA annotation from ARBA model identifies ORC1s chromosomal localization during S phase.'
    action: KEEP_AS_NON_CORE
    reason: 'Correct but redundant with nucleus/nucleoplasm annotations. ORC1 binds chromosomal DNA at replication origins, but this is implicit in its origin binding function. Not a distinct function, rather a cellular location consequence.'
    supported_by: []
- term:
    id: GO:0006260
    label: DNA replication
  evidence_type: IEA
  original_reference_id: GO_REF:0000043
  review:
    summary: 'IEA annotation based on UniProtKB keyword mapping reflects ORC1s essential role in DNA replication process.'
    action: ACCEPT
    reason: 'Core biological process. ORC1 is essential for DNA replication initiation phase. While GO:0006270 (DNA replication initiation) is more specific, this broader term is acceptable for capturing the overall replication process involvement.'
    additional_reference_ids:
      - file:yeast/ORC1/ORC1-deep-research-falcon.md
    supported_by:
      - reference_id: PMID:16824194
        supporting_text: 'Reconstitution of Saccharomyces cerevisiae prereplicative complex assembly in vitro'
      - reference_id: file:yeast/ORC1/ORC1-deep-research-falcon.md
        supporting_text: |-
          ORC binds sequence-defined ARS elements and, together with **Cdc6** and **Cdt1**, loads MCM2–7 to form the pre-RC
- term:
    id: GO:0016887
    label: ATP hydrolysis activity
  evidence_type: IEA
  original_reference_id: GO_REF:0000002
  review:
    summary: 'IEA annotation inferred from InterPro AAA+ ATPase domain (IPR003959). ORC1 catalyzes ATP hydrolysis for nucleotide-dependent conformational changes.'
    action: ACCEPT
    reason: 'Core molecular function. ORC1 is an AAA+ ATPase with documented ATP hydrolysis activity. This is essential for ORC complex assembly, DNA binding, and MCM loading. Experimental evidence (IMP PMID:9038340) supports this. Falcon deep research notes Orc1 is the only ORC subunit experimentally demonstrated to possess ATPase activity, reinforcing this as a core enzymatic function.'
    additional_reference_ids:
      - file:yeast/ORC1/ORC1-deep-research-falcon.md
    supported_by:
      - reference_id: PMID:9038340
        supporting_text: 'Coordinate binding of ATP and origin DNA regulates the ATPase activity of the origin recognition complex'
      - reference_id: file:yeast/ORC1/ORC1-deep-research-falcon.md
        supporting_text: |-
          Orc1 is the only ORC subunit experimentally demonstrated to have ATPase activity
- term:
    id: GO:0046872
    label: metal ion binding
  evidence_type: IEA
  original_reference_id: GO_REF:0000043
  review:
    summary: 'IEA annotation from UniProtKB keyword reflects metal coordination in ORC1s ATP binding sites.'
    action: KEEP_AS_NON_CORE
    reason: 'Technically correct - ORC1 binds Mg(2+) ions at ATP binding sites (documented in UniProt). However, this is a mechanistic detail subordinate to ATP binding and hydrolysis. The more specific ATP-related terms are more informative.'
    supported_by: []
- term:
    id: GO:0005515
    label: protein binding
  evidence_type: IPI
  original_reference_id: PMID:16429126
  review:
    summary: 'IPI annotation from proteome survey identifies ORC1 interactions with ORC complex members and other proteins.'
    action: KEEP_AS_NON_CORE
    reason: 'Generic protein binding annotation. While experimentally supported (IPI), this term lacks specificity. ORC1 has well-characterized interactions with ORC2, ORC3, ORC4, ORC5, ORC6, MCM10, TAH11, and SIR1, but the generic binding term obscures these specific interactions.'
    supported_by:
      - reference_id: PMID:16429126
        supporting_text: 'Proteome survey reveals modularity of the yeast cell machinery'
- term:
    id: GO:0005515
    label: protein binding
  evidence_type: IPI
  original_reference_id: PMID:16554755
  review:
    summary: 'IPI annotation from global protein complex map confirms ORC1 protein-protein interactions.'
    action: KEEP_AS_NON_CORE
    reason: 'Duplicate IPI annotation for generic protein binding. While experimentally valid, this is non-specific. ORC1s binding partners are well-characterized at molecular level but the broad protein binding term is uninformative.'
    supported_by:
      - reference_id: PMID:16554755
        supporting_text: 'Global landscape of protein complexes in the yeast Saccharomyces cerevisiae'
- term:
    id: GO:0005515
    label: protein binding
  evidence_type: IPI
  original_reference_id: PMID:17825065
  review:
    summary: 'IPI annotation from yeast two-hybrid screen documents protein-protein interactions.'
    action: KEEP_AS_NON_CORE
    reason: 'Generic protein binding annotation supported by yeast two-hybrid data. While valid, the term lacks specificity regarding which proteins interact with ORC1.'
    supported_by:
      - reference_id: PMID:17825065
        supporting_text: 'Yeast two-hybrid analysis of the origin recognition complex of Saccharomyces cerevisiae: interaction between subunits and identification of binding proteins'
- term:
    id: GO:0005515
    label: protein binding
  evidence_type: IPI
  original_reference_id: PMID:18647841
  review:
    summary: 'IPI annotation from structural studies of ORC complex architecture documents protein interactions.'
    action: KEEP_AS_NON_CORE
    reason: 'Generic protein binding term. While the cryo-EM structure reveals ORC1 interactions with other ORC subunits, the broad binding term lacks mechanistic specificity.'
    supported_by:
      - reference_id: PMID:18647841
        supporting_text: 'The architecture of the DNA replication origin recognition complex in Saccharomyces cerevisiae'
- term:
    id: GO:0005515
    label: protein binding
  evidence_type: IPI
  original_reference_id: PMID:21179020
  review:
    summary: 'IPI annotation from chromatin-associated interactome defines ORC1 protein associations.'
    action: KEEP_AS_NON_CORE
    reason: 'Generic protein binding. Experimentally supported but non-specific for ORC1s characterized interactions.'
    supported_by:
      - reference_id: PMID:21179020
        supporting_text: 'Defining the budding yeast chromatin-associated interactome'
- term:
    id: GO:0005515
    label: protein binding
  evidence_type: IPI
  original_reference_id: PMID:22405012
  review:
    summary: 'IPI annotation from cryo-EM structural analysis documents ORC1 protein-protein contacts.'
    action: KEEP_AS_NON_CORE
    reason: 'Generic protein binding. Cryo-EM structure reveals detailed ORC subunit interactions, but broad binding term fails to capture this specificity.'
    supported_by:
      - reference_id: PMID:22405012
        supporting_text: 'Cdc6-induced conformational changes in ORC bound to origin DNA revealed by cryo-electron microscopy'
- term:
    id: GO:0005515
    label: protein binding
  evidence_type: IPI
  original_reference_id: PMID:27107014
  review:
    summary: 'IPI annotation from inter-species protein interaction network identifies ORC1 protein interactions.'
    action: KEEP_AS_NON_CORE
    reason: 'Generic protein binding annotation. While documenting evolutionary conservation of protein interactions, the broad term lacks specificity.'
    supported_by:
      - reference_id: PMID:27107014
        supporting_text: 'An inter-species protein-protein interaction network across vast evolutionary distance'
- term:
    id: GO:0005515
    label: protein binding
  evidence_type: IPI
  original_reference_id: PMID:37968396
  review:
    summary: 'IPI annotation from social and structural architecture study confirms ORC1 protein associations.'
    action: KEEP_AS_NON_CORE
    reason: 'Generic protein binding. Recent interactome study confirms ORC1 interactions but the broad term is non-informative.'
    supported_by:
      - reference_id: PMID:37968396
        supporting_text: 'The social and structural architecture of the yeast protein interactome'
- term:
    id: GO:0005515
    label: protein binding
  evidence_type: IPI
  original_reference_id: PMID:8622770
  review:
    summary: 'IPI annotation documents ORC1-SIR1 interaction critical for transcriptional silencing function.'
    action: KEEP_AS_NON_CORE
    reason: 'Generic protein binding annotation. While the ORC1-SIR1 interaction is critical for silent locus silencing (and documented in UniProt interactions), the broad binding term obscures this mechanistically important interaction.'
    supported_by:
      - reference_id: PMID:8622770
        supporting_text: 'Role of interactions between the origin recognition complex and SIR1 in transcriptional silencing'
- term:
    id: GO:0005634
    label: nucleus
  evidence_type: EXP
  original_reference_id: PMID:16824194
  review:
    summary: 'EXP annotation documents nuclear localization of ORC1 from in vitro reconstitution studies.'
    action: KEEP_AS_NON_CORE
    reason: 'Experimentally validated localization. However, nucleus is a broad cellular compartment term. The more specific nucleoplasm annotations (GO:0005654 TAS) and nuclear pre-replicative complex (GO:0005656 IDA) better describe ORC1s functional location.'
    supported_by:
      - reference_id: PMID:16824194
        supporting_text: 'Reconstitution of Saccharomyces cerevisiae prereplicative complex assembly in vitro'
- term:
    id: GO:0006270
    label: DNA replication initiation
  evidence_type: NAS
  original_reference_id: PMID:16824194
  review:
    summary: 'NAS (Not Annotated Source) evidence from reconstitution studies documents ORC1s essential role in initiation.'
    action: ACCEPT
    reason: 'Duplicate annotation for core function with different evidence type (NAS). The in vitro reconstitution studies provide mechanistic support for ORC1s role in pre-replicative complex assembly and DNA replication initiation.'
    supported_by:
      - reference_id: PMID:16824194
        supporting_text: 'Reconstitution of Saccharomyces cerevisiae prereplicative complex assembly in vitro'
- term:
    id: GO:0034728
    label: nucleosome organization
  evidence_type: IMP
  original_reference_id: PMID:37020028
  review:
    summary: 'IMP annotation from recent study characterizes ORC1s role in chromatin organization at replication origins.'
    action: ACCEPT
    reason: 'ORC1s BAH domain mediates nucleosome binding and influences nucleosome positioning at replication origins. This facilitates origin activation and is a documented secondary function. Experimental (IMP) evidence provides functional validation.'
    additional_reference_ids:
      - file:yeast/ORC1/ORC1-deep-research-falcon.md
    supported_by:
      - reference_id: PMID:37020028
        supporting_text: 'Establishment and function of chromatin organization at replication origins'
      - reference_id: file:yeast/ORC1/ORC1-deep-research-falcon.md
        supporting_text: |-
          Structural work shows Orc1 BAH binds the nucleosome core directly
- term:
    id: GO:0005654
    label: nucleoplasm
  evidence_type: TAS
  original_reference_id: Reactome:R-SCE-9749345
  review:
    summary: 'TAS annotation from Reactome identifies nucleoplasm as the functional compartment for MCM loading.'
    action: KEEP_AS_NON_CORE
    reason: 'Correct subcellular localization but redundant with nucleus and nuclear pre-replicative complex annotations. Nucleoplasm is the appropriate compartment for ORC1 function but this is implicit in its replication initiation role.'
    supported_by: []
- term:
    id: GO:0005654
    label: nucleoplasm
  evidence_type: TAS
  original_reference_id: Reactome:R-SCE-9749381
  review:
    summary: 'TAS annotation from Reactome pathway identifies nucleoplasm localization during CDT1 release.'
    action: KEEP_AS_NON_CORE
    reason: 'Correct but redundant subcellular localization. Multiple pathway annotations for nucleoplasm are unnecessary.'
    supported_by: []
- term:
    id: GO:0005654
    label: nucleoplasm
  evidence_type: TAS
  original_reference_id: Reactome:R-SCE-9749401
  review:
    summary: 'TAS annotation from Reactome identifies nucleoplasm during MCM double hexamer formation.'
    action: KEEP_AS_NON_CORE
    reason: 'Correct but redundant subcellular localization. This duplicates the nucleoplasm annotation from other Reactome pathways.'
    supported_by: []
- term:
    id: GO:0031491
    label: nucleosome binding
  evidence_type: IDA
  original_reference_id: PMID:31263106
  review:
    summary: 'IDA annotation directly demonstrates ORC1s BAH domain interaction with nucleosomes.'
    action: ACCEPT
    reason: 'Experimental evidence (IDA) from structural and functional studies. ORC1s BAH domain specifically binds nucleosomes, facilitating nucleosome-mediated origin regulation. This is a characterized and important secondary function.'
    additional_reference_ids:
      - file:yeast/ORC1/ORC1-deep-research-falcon.md
    supported_by:
      - reference_id: PMID:31263106
        supporting_text: 'Structure and function of the Orc1 BAH-nucleosome complex'
      - reference_id: file:yeast/ORC1/ORC1-deep-research-falcon.md
        supporting_text: |-
          A structural study determined the Orc1 BAH–nucleosome complex at **3.3 Å** and reported that Orc1 BAH forms extensive contacts with core histones, **burying ~1590 Å²** of surface
- term:
    id: GO:0043007
    label: maintenance of rDNA
  evidence_type: IDA
  original_reference_id: PMID:31263106
  review:
    summary: 'IDA annotation documents ORC1s role in ribosomal DNA maintenance and nucleosome organization at rDNA loci.'
    action: ACCEPT
    reason: 'Experimental evidence (IDA) supports ORC1s function in rDNA maintenance through nucleosome-based regulation. rDNA regions contain active replication origins and require specialized chromatin organization. This is a characterized secondary function. Falcon deep research adds that Orc1 BAH-nucleosome binding protects rDNA border integrity during meiosis, with reduced BAH affinity increasing double-strand breaks.'
    additional_reference_ids:
      - file:yeast/ORC1/ORC1-deep-research-falcon.md
    supported_by:
      - reference_id: PMID:31263106
        supporting_text: 'Structure and function of the Orc1 BAH-nucleosome complex'
      - reference_id: file:yeast/ORC1/ORC1-deep-research-falcon.md
        supporting_text: |-
          Orc1 BAH–nucleosome interactions contribute to genome stability at rDNA borders during meiosis; reduced Orc1-BAH affinity is associated with increased double-strand breaks
- term:
    id: GO:0003682
    label: chromatin binding
  evidence_type: IDA
  original_reference_id: PMID:11168584
  review:
    summary: 'IDA annotation directly demonstrates ORC1s chromatin binding through interactions with MCM10 and other chromatin factors.'
    action: ACCEPT
    reason: 'Experimental evidence (IDA) for chromatin binding. While not as specific as DNA replication origin binding or nucleosome binding, this annotation correctly captures ORC1s broader chromatin association function.'
    supported_by:
      - reference_id: PMID:11168584
        supporting_text: 'Interactions between Mcm10p and other replication factors are required for proper initiation and elongation of chromosomal DNA replication in Saccharomyces cerevisiae'
- term:
    id: GO:0003688
    label: DNA replication origin binding
  evidence_type: IDA
  original_reference_id: PMID:16824194
  review:
    summary: 'IDA annotation provides direct experimental evidence for ORC1s origin binding function.'
    action: ACCEPT
    reason: 'Core molecular function. Direct assay evidence (IDA) from in vitro reconstitution unequivocally demonstrates ORC1s specific binding to origin DNA at ARS consensus sequences.'
    supported_by:
      - reference_id: PMID:16824194
        supporting_text: 'Reconstitution of Saccharomyces cerevisiae prereplicative complex assembly in vitro'
- term:
    id: GO:0005524
    label: ATP binding
  evidence_type: IDA
  original_reference_id: PMID:17825064
  review:
    summary: 'IDA annotation directly assays ATP binding in ORC1 and Cdt1 interaction studies.'
    action: ACCEPT
    reason: 'Core molecular function. Direct experimental evidence (IDA) confirms ATP binding. This is mechanistically essential for ORC1s regulatory ATPase activity.'
    supported_by:
      - reference_id: PMID:17825064
        supporting_text: 'Interaction between ORC and Cdt1p of Saccharomyces cerevisiae'
- term:
    id: GO:0005524
    label: ATP binding
  evidence_type: IMP
  original_reference_id: PMID:9038340
  review:
    summary: 'IMP annotation documents ATP binding as essential for ORC complex ATPase activity regulation.'
    action: ACCEPT
    reason: 'Core function. Mutational/functional evidence (IMP) shows ATP binding is required for coordinate regulation of origin binding and ATPase activity. Duplicates the IDA annotation but different evidence code validates importance.'
    supported_by:
      - reference_id: PMID:9038340
        supporting_text: 'Coordinate binding of ATP and origin DNA regulates the ATPase activity of the origin recognition complex'
- term:
    id: GO:0005634
    label: nucleus
  evidence_type: IDA
  original_reference_id: PMID:11168584
  review:
    summary: 'IDA annotation directly demonstrates nuclear localization of ORC1.'
    action: KEEP_AS_NON_CORE
    reason: 'Experimental validation of nuclear localization. However, this broad cellular component term is less informative than the nuclear pre-replicative complex and nucleoplasm annotations that specify ORC1s functional compartments.'
    supported_by:
      - reference_id: PMID:11168584
        supporting_text: 'Interactions between Mcm10p and other replication factors are required for proper initiation and elongation of chromosomal DNA replication in Saccharomyces cerevisiae'
- term:
    id: GO:0005656
    label: nuclear pre-replicative complex
  evidence_type: IDA
  original_reference_id: PMID:16824194
  review:
    summary: 'IDA annotation directly identifies ORC1 as a structural component of the pre-replicative complex.'
    action: ACCEPT
    reason: 'Core cellular component. ORC1 is a required component of the nuclear pre-replicative complex (pre-RC) that forms at G1. Experimental evidence (IDA) from in vitro reconstitution and cellular studies confirms this.'
    supported_by:
      - reference_id: PMID:16824194
        supporting_text: 'Reconstitution of Saccharomyces cerevisiae prereplicative complex assembly in vitro'
- term:
    id: GO:0005656
    label: nuclear pre-replicative complex
  evidence_type: IDA
  original_reference_id: PMID:9335335
  review:
    summary: 'IDA annotation from cell cycle studies documents ORC1 as core component of pre-RC during S phase.'
    action: ACCEPT
    reason: 'Duplicate annotation for core component. Experimental evidence (IDA) from MCM protein redistribution studies confirms ORC1s role in pre-RC assembly and dynamics.'
    supported_by:
      - reference_id: PMID:9335335
        supporting_text: 'Components and dynamics of DNA replication complexes in S. cerevisiae: redistribution of MCM proteins and Cdc45p during S phase'
- term:
    id: GO:0005664
    label: nuclear origin of replication recognition complex
  evidence_type: IDA
  original_reference_id: PMID:9372948
  review:
    summary: 'IDA annotation directly identifies ORC1 as integral component of the ORC complex through structural analysis.'
    action: ACCEPT
    reason: 'Core cellular component. ORC1 is essential to ORC complex assembly. Experimental evidence (IDA) from origin-bound ORC architecture studies provides direct confirmation.'
    supported_by:
      - reference_id: PMID:9372948
        supporting_text: 'Architecture of the yeast origin recognition complex bound to origins of DNA replication'
- term:
    id: GO:0005664
    label: nuclear origin of replication recognition complex
  evidence_type: IMP
  original_reference_id: PMID:9372948
  review:
    summary: 'IMP annotation documents ORC1s functional role in ORC complex assembly through mutational analysis.'
    action: ACCEPT
    reason: 'Core component. Duplicate annotation with different evidence type (IMP). Functional mutations demonstrate ORC1s essential role in complex formation and origin recognition.'
    supported_by:
      - reference_id: PMID:9372948
        supporting_text: 'Architecture of the yeast origin recognition complex bound to origins of DNA replication'
- term:
    id: GO:0006267
    label: pre-replicative complex assembly involved in nuclear cell cycle DNA replication
  evidence_type: IDA
  original_reference_id: PMID:16824194
  review:
    summary: 'IDA annotation directly demonstrates ORC1s active role in pre-replicative complex assembly through in vitro reconstitution.'
    action: ACCEPT
    reason: 'Core biological process. ORC1 is the rate-limiting or nucleation factor for pre-RC assembly. Experimental evidence (IDA, IMP) from multiple studies unambiguously supports this essential function.'
    additional_reference_ids:
      - file:yeast/ORC1/ORC1-deep-research-falcon.md
    supported_by:
      - reference_id: PMID:16824194
        supporting_text: 'Reconstitution of Saccharomyces cerevisiae prereplicative complex assembly in vitro'
      - reference_id: file:yeast/ORC1/ORC1-deep-research-falcon.md
        supporting_text: |-
          ORC bends DNA at origin elements in a manner that helps align and insert DNA into the MCM ring during formation of helicase-loading intermediates
- term:
    id: GO:0006267
    label: pre-replicative complex assembly involved in nuclear cell cycle DNA replication
  evidence_type: IMP
  original_reference_id: PMID:9335335
  review:
    summary: 'IMP annotation from cell cycle studies documents ORC1s essential role in pre-RC assembly.'
    action: ACCEPT
    reason: 'Duplicate annotation for core process. Experimental evidence (IMP) from MCM redistribution and functional studies confirms ORC1s requirement for pre-RC assembly.'
    supported_by:
      - reference_id: PMID:9335335
        supporting_text: 'Components and dynamics of DNA replication complexes in S. cerevisiae: redistribution of MCM proteins and Cdc45p during S phase'
- term:
    id: GO:0006270
    label: DNA replication initiation
  evidence_type: IMP
  original_reference_id: PMID:16716188
  review:
    summary: 'IMP annotation documents ORC1s essential role in DNA replication initiation through checkpoint and cell cycle execution point analysis.'
    action: ACCEPT
    reason: 'Core biological process. Conditional inactivation of ORC (including ORC1) results in failure of replication initiation, confirming essential role.'
    supported_by:
      - reference_id: PMID:16716188
        supporting_text: 'Cell cycle execution point analysis of ORC function and characterization of the checkpoint response to ORC inactivation in Saccharomyces cerevisiae'
- term:
    id: GO:0016887
    label: ATP hydrolysis activity
  evidence_type: IMP
  original_reference_id: PMID:9038340
  review:
    summary: 'IMP annotation demonstrates ATP hydrolysis activity is functionally essential for ORC1s regulatory mechanism.'
    action: ACCEPT
    reason: 'Core molecular function. Experimental evidence (IMP) shows ORC1s ATP hydrolysis is required for complex assembly and origin regulation. Mutations affecting ATPase activity impair ORC function.'
    supported_by:
      - reference_id: PMID:9038340
        supporting_text: 'Coordinate binding of ATP and origin DNA regulates the ATPase activity of the origin recognition complex'
- term:
    id: GO:0030466
    label: silent mating-type cassette heterochromatin formation
  evidence_type: IDA
  original_reference_id: PMID:12897051
  review:
    summary: 'IDA annotation directly demonstrates ORC1s role in transcriptional silencing at HMR/HML loci.'
    action: ACCEPT
    reason: 'Core function. ORC1s interaction with SIR1 and other SIR proteins is essential for establishing heterochromatin at silent mating-type loci. Experimental evidence (IDA) from differential DNA affinity studies confirms this role. Falcon deep research clarifies the mechanism: the Orc1 BAH domain binds silencer elements and recruits Sir1, which nucleates the Sir2/Sir3/Sir4 silencing machinery, and shows this silencing-locus binding is genetically separable from origin binding (BAH deletion abolishes silencing-site binding but not origin binding).'
    additional_reference_ids:
      - file:yeast/ORC1/ORC1-deep-research-falcon.md
    supported_by:
      - reference_id: PMID:12897051
        supporting_text: 'Differential DNA affinity specifies roles for the origin recognition complex in budding yeast heterochromatin'
      - reference_id: file:yeast/ORC1/ORC1-deep-research-falcon.md
        supporting_text: |-
          Orc1 BAH binds at DNA silencer elements and recruits **Sir1**, which then helps recruit the Sir2/Sir3/Sir4 silencing machinery
      - reference_id: file:yeast/ORC1/ORC1-deep-research-falcon.md
        supporting_text: |-
          Orc1 lacking the BAH domain is **lost from silencing-associated sites but remains bound to replication origins**
- term:
    id: GO:0030466
    label: silent mating-type cassette heterochromatin formation
  evidence_type: IDA
  original_reference_id: PMID:16581798
  review:
    summary: 'IDA annotation directly confirms ORC1-SIR3 interaction in heterochromatin establishment.'
    action: ACCEPT
    reason: 'Duplicate annotation for core silencing function. Experimental evidence (IDA) from Sir3 BAH domain structure studies demonstrates ORC1s functional role in recruiting silencing machinery.'
    supported_by:
      - reference_id: PMID:16581798
        supporting_text: 'Structure and function of the Saccharomyces cerevisiae Sir3 BAH domain'
- term:
    id: GO:0030466
    label: silent mating-type cassette heterochromatin formation
  evidence_type: IGI
  original_reference_id: PMID:16581798
  review:
    summary: 'IGI annotation documents genetic interaction between ORC1 and SIR3 in heterochromatin formation.'
    action: ACCEPT
    reason: 'Genetic interaction evidence (IGI) supports ORC1s role in silencing. ORC1-SIR3 genetic interaction (with SGD:S000001809 = SIR3) demonstrates functional interdependence in establishing silent loci.'
    supported_by:
      - reference_id: PMID:16581798
        supporting_text: 'Structure and function of the Saccharomyces cerevisiae Sir3 BAH domain'
- term:
    id: GO:0031261
    label: DNA replication preinitiation complex
  evidence_type: IDA
  original_reference_id: PMID:9554851
  review:
    summary: 'IDA annotation directly identifies ORC1 as component of preinitiation complex formed during S phase.'
    action: ACCEPT
    reason: 'Related to core function. ORC1 is part of the pre-initiation complex (loaded Cdc45). Experimental evidence (IDA) confirms ORC1s presence in this complex. Closely related to pre-replicative complex annotations.'
    supported_by:
      - reference_id: PMID:9554851
        supporting_text: 'Formation of a preinitiation complex by S-phase cyclin CDK-dependent loading of Cdc45p onto chromatin'
references:
- id: GO_REF:0000002
  title: Gene Ontology annotation through association of InterPro records with GO
    terms
  findings: []
- id: GO_REF:0000033
  title: Annotation inferences using phylogenetic trees
  findings: []
- id: GO_REF:0000043
  title: Gene Ontology annotation based on UniProtKB/Swiss-Prot keyword mapping
  findings: []
- id: GO_REF:0000044
  title: Gene Ontology annotation based on UniProtKB/Swiss-Prot Subcellular Location
    vocabulary mapping, accompanied by conservative changes to GO terms applied by
    UniProt
  findings: []
- id: GO_REF:0000117
  title: Electronic Gene Ontology annotations created by ARBA machine learning models
  findings: []
- id: GO_REF:0000120
  title: Combined Automated Annotation using Multiple IEA Methods
  findings: []
- id: PMID:8622770
  title: Role of interactions between the origin recognition complex and SIR1 in transcriptional
    silencing.
  findings: []
- id: PMID:9038340
  title: Coordinate binding of ATP and origin DNA regulates the ATPase activity of
    the origin recognition complex.
  findings: []
- id: PMID:9335335
  title: 'Components and dynamics of DNA replication complexes in S. cerevisiae: redistribution
    of MCM proteins and Cdc45p during S phase.'
  findings: []
- id: PMID:9372948
  title: Architecture of the yeast origin recognition complex bound to origins of
    DNA replication.
  findings: []
- id: PMID:9554851
  title: Formation of a preinitiation complex by S-phase cyclin CDK-dependent loading
    of Cdc45p onto chromatin.
  findings: []
- id: PMID:11168584
  title: Interactions between Mcm10p and other replication factors are required for
    proper initiation and elongation of chromosomal DNA replication in Saccharomyces
    cerevisiae.
  findings: []
- id: PMID:12897051
  title: Differential DNA affinity specifies roles for the origin recognition complex
    in budding yeast heterochromatin.
  findings: []
- id: PMID:16429126
  title: Proteome survey reveals modularity of the yeast cell machinery.
  findings: []
- id: PMID:16554755
  title: Global landscape of protein complexes in the yeast Saccharomyces cerevisiae.
  findings: []
- id: PMID:16581798
  title: Structure and function of the Saccharomyces cerevisiae Sir3 BAH domain.
  findings: []
- id: PMID:16716188
  title: Cell cycle execution point analysis of ORC function and characterization
    of the checkpoint response to ORC inactivation in Saccharomyces cerevisiae.
  findings: []
- id: PMID:16824194
  title: Reconstitution of Saccharomyces cerevisiae prereplicative complex assembly
    in vitro.
  findings: []
- id: PMID:17825064
  title: Interaction between ORC and Cdt1p of Saccharomyces cerevisiae.
  findings: []
- id: PMID:17825065
  title: 'Yeast two-hybrid analysis of the origin recognition complex of Saccharomyces
    cerevisiae: interaction between subunits and identification of binding proteins.'
  findings: []
- id: PMID:18647841
  title: The architecture of the DNA replication origin recognition complex in Saccharomyces
    cerevisiae.
  findings: []
- id: PMID:21179020
  title: Defining the budding yeast chromatin-associated interactome.
  findings: []
- id: PMID:22405012
  title: Cdc6-induced conformational changes in ORC bound to origin DNA revealed by
    cryo-electron microscopy.
  findings: []
- id: PMID:27107014
  title: An inter-species protein-protein interaction network across vast evolutionary
    distance.
  findings: []
- id: PMID:31263106
  title: Structure and function of the Orc1 BAH-nucleosome complex.
  findings: []
- id: PMID:37020028
  title: Establishment and function of chromatin organization at replication origins.
  findings: []
- id: PMID:37968396
  title: The social and structural architecture of the yeast protein interactome.
  findings: []
- id: Reactome:R-SCE-9749345
  title: CDT1-mediated loading of MCM2-7 to replication origin in budding yeast
  findings: []
- id: Reactome:R-SCE-9749381
  title: ATP-dependent release of CDT1 from the OCCM complex in budding yeast
  findings: []
- id: Reactome:R-SCE-9749401
  title: CTD1-mediated formation of MCM2-7 double hexamers at the replication origins
    in budding yeast
  findings: []
- id: file:yeast/ORC1/ORC1-deep-research-falcon.md
  title: Falcon deep research report on ORC1 (yeast)
  findings:
  - statement: |
      Orc1 (YML065W; UniProt P54784) is the largest, ~914-aa subunit of the heterohexameric
      origin recognition complex (ORC, Orc1-6), with an N-terminal BAH domain and a
      C-terminal AAA+ ATPase region.
    supporting_text: |-
      encodes **Origin Recognition Complex subunit 1 (Orc1)**, a ~914-aa protein that is part of the heterohexameric ORC (Orc1–6)
    reference_section_type: OTHER
  - statement: |
      Orc1 has two separable functional modules: an AAA+ initiator module for ATP-dependent
      origin recognition/licensing, and an N-terminal BAH chromatin-binding module that
      mediates nucleosome binding and recruitment to silencing-associated chromatin.
    supporting_text: |-
      an **AAA+ initiator module** contributing to ATP-dependent origin recognition/licensing, and an N-terminal **BAH chromatin-binding module** that mediates nucleosome binding and recruitment to silencing-associated chromatin sites
    reference_section_type: OTHER
  - statement: |
      Orc1 is the only ORC subunit experimentally demonstrated to have ATPase activity,
      and ATP binding by Orc1 is required for ORC DNA binding, while ATP hydrolysis is
      not always required for the binding step itself.
    supporting_text: |-
      Functional evidence further indicates that **ATP binding by Orc1 is required for ORC DNA binding**, while ATP hydrolysis is not always required for the binding step itself
    reference_section_type: OTHER
  - statement: |
      ORC binds sequence-defined ARS elements and, with Cdc6 and Cdt1, loads MCM2-7 to
      form the pre-replicative complex; in early G1 ORC recruits Cdc6 then Cdt1-MCM2-7,
      loading MCM one hexamer at a time into a head-to-head double hexamer.
    supporting_text: |-
      In early G1, ORC (including Orc1) recruits **Cdc6**, then **Cdt1–MCM2–7**, loading MCM one hexamer at a time to form a head-to-head MCM double hexamer
    reference_section_type: OTHER
  - statement: |
      The Orc1 BAH-nucleosome complex was solved at 3.3 Angstrom, with BAH making
      extensive contacts to core histones and burying ~1590 square Angstrom of surface;
      unlike Sir3, Orc1 BAH does not strongly discriminate H4K16 acetylation state.
    supporting_text: |-
      A structural study determined the Orc1 BAH–nucleosome complex at **3.3 Å** and reported that Orc1 BAH forms extensive contacts with core histones, **burying ~1590 Å²** of surface
    reference_section_type: OTHER
  - statement: |
      At HM silencers, the Orc1 BAH domain binds silencer elements and recruits Sir1,
      which helps recruit the Sir2/Sir3/Sir4 silencing machinery to nucleate
      heterochromatin.
    supporting_text: |-
      Orc1 BAH binds at DNA silencer elements and recruits **Sir1**, which then helps recruit the Sir2/Sir3/Sir4 silencing machinery
    reference_section_type: OTHER
  - statement: |
      Orc1's origin-binding and silencing-locus-binding determinants are genetically
      separable: deletion of the BAH domain abolishes binding at silencing-associated
      sites but Orc1 remains bound to replication origins.
    supporting_text: |-
      Orc1 lacking the BAH domain is **lost from silencing-associated sites but remains bound to replication origins**
    reference_section_type: OTHER
  - statement: |
      Orc1 BAH-nucleosome interactions protect rDNA border integrity during meiosis;
      reduced Orc1-BAH affinity is associated with increased double-strand breaks.
    supporting_text: |-
      Orc1 BAH–nucleosome interactions contribute to genome stability at rDNA borders during meiosis; reduced Orc1-BAH affinity is associated with increased double-strand breaks
    reference_section_type: OTHER
  - statement: |
      Licensing (MCM loading) is restricted to early G1; after G1, CDK-dependent
      phosphorylation inhibits re-licensing to prevent rereplication.
    supporting_text: |-
      the **licensing reaction (MCM loading)** is concentrated in **early G1**; after G1, **CDK-dependent phosphorylation** inhibits re-licensing to prevent rereplication
    reference_section_type: OTHER
  - statement: |
      Budding yeast uses sequence-specific ORC recognition at ARS elements, whereas
      human ORC is more strongly guided by chromatin landscape, so lineage-specific
      features (e.g. the Orc4 insertion helix) should not be naively extrapolated.
    supporting_text: |-
      yeast uses sequence-specific ORC recognition at ARSs, whereas human ORC is more strongly guided by chromatin landscape
    reference_section_type: OTHER
core_functions:
- molecular_function:
    id: GO:0003688
    label: DNA replication origin binding
  description: 'ORC1 specifically recognizes and binds ARS consensus sequences (ACS) at chromosomal replication origins through its DBD domain. This is the initiating event for all replication origin function.'
  directly_involved_in:
    - id: GO:0006270
      label: DNA replication initiation
  supported_by:
    - reference_id: PMID:16824194
      supporting_text: 'Reconstitution of Saccharomyces cerevisiae prereplicative complex assembly in vitro'
- molecular_function:
    id: GO:0016887
    label: ATP hydrolysis activity
  description: 'ORC1 catalyzes ATP hydrolysis, which provides the energy for conformational changes required for origin binding, MCM loading, and complex assembly during pre-RC formation at G1.'
  directly_involved_in:
    - id: GO:0006267
      label: pre-replicative complex assembly involved in nuclear cell cycle DNA replication
  in_complex:
    id: GO:0005664
    label: nuclear origin of replication recognition complex
  supported_by:
    - reference_id: file:yeast/ORC1/ORC1-deep-research-falcon.md
      supporting_text: |-
        Orc1 is the only ORC subunit experimentally demonstrated to have ATPase activity
- molecular_function:
    id: GO:0031491
    label: nucleosome binding
  description: 'ORC1s BAH domain mediates specific nucleosome binding, which facilitates proper nucleosome positioning at replication origins and coordinates chromatin organization with replication initiation.'
  directly_involved_in:
    - id: GO:0034728
      label: nucleosome organization
  supported_by:
    - reference_id: PMID:31263106
      supporting_text: 'Structure and function of the Orc1 BAH-nucleosome complex'
proposed_new_terms: []
suggested_questions:
- question: 'What is the functional role of ORC1s N-terminal domain versus C-terminal ATPase domain in origin recognition versus silencing?'
- question: 'How does ORC1s BAH domain nucleosome binding affect MCM loading efficiency and origin firing timing?'
- question: 'Why does ORC1 have dual roles in both replication initiation and transcriptional silencing - are these mechanistically linked?'
suggested_experiments:
- description: 'Structural analysis of ORC1 bound to both origin DNA and nucleosomes simultaneously to understand coordination'
  experiment_type: 'Structural biology (Cryo-EM, X-ray crystallography)'
- description: 'Single-molecule studies of MCM loading kinetics with wild-type versus nucleosome-binding deficient ORC1'
  experiment_type: 'Biophysics'
- description: 'Quantitative analysis of SIR protein recruitment and heterochromatin spreading at silent loci versus origin binding sites'
  experiment_type: 'Quantitative cell biology'

Gene Description

Existing Annotations Review

Core Functions

ORC1 specifically recognizes and binds ARS consensus sequences (ACS) at chromosomal replication origins through its DBD domain. This is the initiating event for all replication origin function.

ORC1 catalyzes ATP hydrolysis, which provides the energy for conformational changes required for origin binding, MCM loading, and complex assembly during pre-RC formation at G1.

ORC1s BAH domain mediates specific nucleosome binding, which facilitates proper nucleosome positioning at replication origins and coordinates chromatin organization with replication initiation.

References

Suggested Questions for Experts

Suggested Experiments

Deep Research

Falcon

Research Report: Functional Annotation of ORC1 (UniProt P54784; ORC1/YML065W) in Saccharomyces cerevisiae (S288c)

1) Verification of correct gene/protein target

2) Key concepts and definitions (current understanding)

Origin Recognition Complex (ORC) and origin licensing

ARS/ACS elements

Orc1 modularity: AAA+ initiator vs BAH chromatin adapter

3) Primary molecular functions of Orc1 (substrates, activities, and mechanism)

3.1 ATPase and ATP-dependent origin recognition (substrate: ATP; macromolecular substrate: origin dsDNA)

3.2 DNA binding and origin architecture (substrate: specific dsDNA motifs and local DNA shape)

3.3 Pre-RC assembly and helicase loading (interactions: Cdc6, Cdt1–Mcm2–7)

4) Orc1 roles in chromatin biology and transcriptional silencing (BAH domain)

4.1 Orc1 BAH domain binds nucleosomes (substrate: nucleosome core particle / histone tails)

4.2 Sir1 recruitment and HM silencing

4.3 Telomeres and silent chromatin architecture beyond silencers

4.4 rDNA border integrity (meiosis)

5) Cellular localization and cell-cycle regulation

Chromatin association across the cell cycle and G1-restricted licensing

Recent regulatory mechanisms (2024)

6) Recent developments and latest research (priority 2023–2024)

6.1 High-resolution structural era integrated with genome-wide mutant mapping

6.2 Distinguishing replication-origin binding from silencing-associated binding

7) Current applications and real-world implementations

8) Expert synthesis and authoritative perspectives

9) Key statistics and data points (from cited studies)

10) Summary functional annotation (evidence-backed)

Evidence limitations (explicitly noted)

Embedded summary table

Artifacts

Citations

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