EZ1

Existing Annotations Review

GO Term	Evidence	Action	Reason
GO:0032259 methylation	IEA GO_REF:0000043	MARK AS OVER ANNOTATED	Summary: SPKW (GO_REF:0000043) annotation derived from the UniProt keyword "Methyltransferase"/"Transferase"; snapshot-only, removed in the current GOA release. EZ1/MEZ1 is genuinely a methyltransferase, but "methylation" is the generic process term that drops the substrate: the enzyme specifically performs histone H3 Lys-27 methylation. Reason: GOA's removal of this annotation was JUSTIFIED. The keyword-derived term "methylation" (GO:0032259) is the high-level parent process that simply states a methyl group is transferred, dropping all substrate specificity. EZ1/MEZ1 is an E(z)-class enzyme whose UniProt FUNCTION explicitly states it "methylates 'Lys-27' of histone H3", i.e. it performs substrate-specific histone H3K27 methylation as a SAM-dependent histone lysine methyltransferase acting on H3K27. The substrate specificity is already captured by the molecular-function terms retained in current GOA - "histone H3K27 methyltransferase activity" (GO:0046976) and "histone H3K27 trimethyltransferase activity" (GO:0140951) - and the biological role is captured by "heterochromatin formation" (GO:0031507) and "negative regulation of gene expression, epigenetic" (GO:0045814). The bare "methylation" process term therefore adds no information once these specific annotations are present. It cannot be usefully MODIFIED to a specific histone-methylation process term either, because the candidate substrate-specific process terms in GO ("histone H3-K27 methylation" GO:0070734 and "histone methylation" GO:0016571) are now obsolete - GO carries the substrate specificity on the molecular-function branch rather than as a dedicated process. Removal of the redundant generic keyword-derived term is appropriate (over-annotation). Supporting Evidence: file:MAIZE/EZ1/EZ1-deep-research-falcon.md its expected enzymatic role is to use S-adenosylmethionine (SAM) to methylate histone H3 Lys-27, producing H3K27me3 on chromatin within PRC2 file:MAIZE/EZ1/EZ1-deep-research-falcon.md PRC2 catalyzes H3K27 trimethylation (H3K27me3)
GO:0003682 chromatin binding	IBA GO_REF:0000033	ACCEPT	Summary: IBA annotation propagated across the E(z)/EZH phylogenetic group. As a PRC2 catalytic subunit, EZ1/MEZ1 associates with chromatin (nucleosomes) to deposit H3K27 methylation. Reason: Appropriate and well supported by conserved biology. PRC2 is a chromatin-associated nuclear complex that deposits histone methylation on nucleosomes at genomic loci, so chromatin binding is a genuine, conserved molecular activity of the E(z)/EZH family. The IBA term is at the right level of specificity and consistent with the EZ1 SANT and CXC chromatin-engaging modules described for the maize MEZ proteins. Supporting Evidence: file:MAIZE/EZ1/EZ1-deep-research-falcon.md PRC2-dependent deposition of H3K27me3 is a chromatin-associated nuclear process file:MAIZE/EZ1/EZ1-deep-research-falcon.md PRC2 complex subunits are required for nucleosome association of PRC2
GO:0031507 heterochromatin formation	IBA GO_REF:0000033	ACCEPT	Summary: IBA annotation: the E(z)/PRC2 family establishes repressive (facultative heterochromatin) chromatin states via H3K27me3. This is a core biological process of EZ1/MEZ1. Reason: Core function, strongly supported by conserved plant PRC2 biology and maize-specific epigenomics. Plant PRC2 deposits H3K27 methylation that establishes a repressive chromatin state at target loci, and maize H3K27me3 marks define facultative heterochromatin and are attributed to the E(z)/PRC2 pathway. The IBA term is at an appropriate level of specificity for an E(z)-class catalytic subunit. Supporting Evidence: file:MAIZE/EZ1/EZ1-deep-research-falcon.md Genomic distribution of maize facultative heterochromatin marked by trimethylation of H3K27 file:MAIZE/EZ1/EZ1-deep-research-falcon.md Maize H3K27me3 is tissue-variable and enriched in gene-dense chromosome arms
GO:0005634 nucleus	IEA GO_REF:0000120	ACCEPT	Summary: IEA annotation for nuclear localization, consistent with the UniProt subcellular location ("Nucleus") and with PRC2 being a chromatin-associated nuclear complex. Reason: Correct and well supported. The UniProt entry assigns subcellular location "Nucleus", and PRC2 is inherently a chromatin-associated nuclear complex because it deposits histone methylation on nucleosomes; genome-wide analyses report that most PRC2 proteins localize to the nucleus. Although maize-specific localization microscopy for MEZ1 was not retrieved, the conservative inference is strong. Supporting Evidence: file:MAIZE/EZ1/EZ1-deep-research-falcon.md most PRC2 core proteins localize to the nucleus and physically interact to form multi-subunit complexes file:MAIZE/EZ1/EZ1-deep-research-falcon.md maize PRC2 core subunits (including E(z)/MEZ family proteins) are nuclear/chromatin-associated
GO:0006338 chromatin remodeling	IEA GO_REF:0000002	MODIFY	Summary: IEA annotation from InterPro (IPR045318, EZH1/2-like). "Chromatin remodeling" is an imprecise process term for a histone methyltransferase whose action is covalent H3K27 methylation, not ATP-dependent nucleosome repositioning. Reason: The essence (EZ1 alters chromatin state) is correct, but "chromatin remodeling" (GO:0006338) conventionally denotes dynamic, often ATP-dependent reorganization of nucleosome structure, whereas EZ1/MEZ1 acts by depositing a covalent histone mark (H3K27 methylation) to establish a repressive chromatin state. The biology is more precisely captured by "heterochromatin formation" (GO:0031507), which is the established process for E(z)/PRC2-mediated H3K27me3 silencing and is already present via the IBA annotation. Modify to the more specific and accurate process term. Proposed replacements: heterochromatin formation Supporting Evidence: file:MAIZE/EZ1/EZ1-deep-research-falcon.md PRC2 catalyzes H3K27 trimethylation (H3K27me3) file:MAIZE/EZ1/EZ1-deep-research-falcon.md Genomic distribution of maize facultative heterochromatin marked by trimethylation of H3K27
GO:0031519 PcG protein complex	IEA GO_REF:0000120	ACCEPT	Summary: IEA annotation: EZ1/MEZ1 is part of a Polycomb group (PcG) protein complex (PRC2). This is a core cellular-component annotation for an E(z)-class catalytic subunit. Reason: Correct and core. The UniProt FUNCTION states EZ1 is a Polycomb group protein and the catalytic subunit of "some PcG multiprotein complex"; plant E(z)-class proteins function within PRC2-like assemblies that include FIE/MSI1/SU(Z)12-like subunits. In maize, EZ1/MEZ1 is most plausibly functional as part of PRC2-like complexes. The term is at an appropriate level of specificity for complex membership. Supporting Evidence: file:MAIZE/EZ1/EZ1-deep-research-falcon.md ZmMEZ1 is highly expressed together with ZmFie1, ZmEmf2b, ZmMSI1c, supporting participation in a grain-filling PRC2 complex PMID:11950982 Polycomb group (PcG) proteins play an important role in developmental and
GO:0042054 histone methyltransferase activity	IEA GO_REF:0000002	MODIFY	Summary: IEA annotation from InterPro (IPR045318, EZH1/2-like). EZ1/MEZ1 is a histone methyltransferase, but the substrate-specific child term "histone H3K27 methyltransferase activity" (GO:0046976) is more informative and is already present. Reason: The annotation is correct but too general. EZ1/MEZ1 is an E(z)-class enzyme that specifically methylates Lys-27 of histone H3; the deep research concludes it is a SAM-dependent histone lysine methyltransferase acting on H3K27, consistent with its EC assignment in UniProt (EC 2.1.1.356) and its E(z)-class SET domain conservation. The generic "histone methyltransferase activity" should be modified to the substrate-specific "histone H3K27 methyltransferase activity" (GO:0046976), which is already annotated (IBA/IEA) and captures the true catalytic specificity. Proposed replacements: histone H3K27 methyltransferase activity Supporting Evidence: file:MAIZE/EZ1/EZ1-deep-research-falcon.md its expected enzymatic role is to use S-adenosylmethionine (SAM) to methylate histone H3 Lys-27, producing H3K27me3 on chromatin within PRC2 file:MAIZE/EZ1/EZ1-deep-research-falcon.md E(z)-family SET-domain proteins (e.g., CLF/SWN/MEA in Arabidopsis) as the catalytic subunits responsible for depositing H3K27me3
GO:0140951 histone H3K27 trimethyltransferase activity	IEA GO_REF:0000120	ACCEPT	Summary: IEA annotation transferred from EC 2.1.1.356 (UniProtKB-EC). This is the most specific molecular-function term and matches the UniProt catalytic activity (formation of H3K27me3). Reason: Correct and maximally specific. The UniProt CATALYTIC ACTIVITY record assigns EC 2.1.1.356 (L-lysyl(27)-[histone H3] + 3 SAM -> trimethyl-L-lysyl(27)-[histone H3]), i.e. histone H3K27 trimethyltransferase activity, and the deep research confirms EZ1 is a SAM-dependent histone lysine methyltransferase acting on H3K27 consistent with its EC assignment in UniProt. This is a core molecular function; accept as-is. Supporting Evidence: file:MAIZE/EZ1/EZ1-deep-research-falcon.md PRC2 catalyzes H3K27 trimethylation (H3K27me3) file:MAIZE/EZ1/EZ1-deep-research-falcon.md its expected enzymatic role is to use S-adenosylmethionine (SAM) to methylate histone H3 Lys-27, producing H3K27me3 on chromatin within PRC2
GO:0001222 transcription corepressor binding	IEA GO_REF:0000107	MARK AS OVER ANNOTATED	Summary: IEA annotation transferred from the Arabidopsis ortholog (AT2G23380 = SWN, P93831) by Ensembl Compara. "Transcription corepressor binding" is a non-specific protein-binding term with no maize-specific support and is not part of the gene's core methyltransferase function. Reason: This is an orthology-transferred protein-binding annotation lacking gene-specific support in maize. The retrieved literature does not identify a specific corepressor partner of EZ1/MEZ1; the gene's well-supported molecular function is its E(z)-class H3K27 methyltransferase activity within PRC2. "Protein binding"-type terms that do not identify an informative interaction partner are discouraged and add little once the catalytic MF and PcG-complex membership are annotated. Treat as an over-annotation pending direct interaction evidence. Supporting Evidence: file:MAIZE/EZ1/EZ1-deep-research-falcon.md E(z)-family SET-domain proteins (e.g., CLF/SWN/MEA in Arabidopsis) as the catalytic subunits responsible for depositing H3K27me3
GO:0003727 single-stranded RNA binding	IEA GO_REF:0000107	REMOVE	Summary: IEA annotation transferred from the Arabidopsis ortholog (AT2G23380 = SWN) by Ensembl Compara. There is no maize-specific evidence that EZ1/MEZ1 binds single-stranded RNA, and this is not part of its supported function. Reason: Unsupported orthology transfer. While PRC2 RNA association has been reported in some systems, it is mechanistically contested and there is no maize-specific evidence that EZ1/MEZ1 binds single-stranded RNA. The retrieved literature characterizes EZ1/MEZ1 strictly as a chromatin-associated, nuclear E(z)-class histone methyltransferase acting on H3K27; no RNA-binding assay supports this term for the maize protein. A speculative, ortholog-transferred ssRNA-binding MF that is not part of the gene's demonstrated function should be removed. Supporting Evidence: file:MAIZE/EZ1/EZ1-deep-research-falcon.md PRC2-dependent deposition of H3K27me3 is a chromatin-associated nuclear process
GO:0005677 chromatin silencing complex	IEA GO_REF:0000107	ACCEPT	Summary: IEA annotation (Ensembl ortholog transfer; also present via EnsemblPlants in the UniProt record). EZ1/MEZ1 is part of a PRC2 chromatin-silencing complex that establishes repressive H3K27me3 chromatin. Reason: Consistent with the gene's role. Plant PRC2 is a chromatin-silencing complex that deposits H3K27 methylation to establish a repressive chromatin state at target loci, mediating transcriptional repression; EZ1/MEZ1 is the catalytic subunit of such a PcG complex per UniProt. This complex-membership term is appropriate and overlaps with the PcG protein complex annotation. Supporting Evidence: file:MAIZE/EZ1/EZ1-deep-research-falcon.md classification into the four core groups (E(z), Su(z)12, ESC, p55/MSI), nuclear localization of components PMID:11950982 these genes likely play a conserved role in repressing gene expression
GO:0006355 regulation of DNA-templated transcription	IEA GO_REF:0000107	MODIFY	Summary: IEA annotation (Ensembl ortholog transfer). EZ1/MEZ1 regulates transcription, but this is a very generic process term; its action is specifically epigenetic transcriptional repression. Reason: The essence is correct (EZ1 affects transcription) but the term is overly general. EZ1/MEZ1 acts by depositing repressive H3K27 methylation leading to transcriptional repression of target genes (UniProt FUNCTION), i.e. it mediates epigenetic negative regulation of gene expression. The more specific and informative term "negative regulation of gene expression, epigenetic" (GO:0045814) - which is already present as a separate IEA annotation - better captures this directional, mechanism- specific role. Modify the generic transcription-regulation term to the epigenetic negative-regulation term. Proposed replacements: negative regulation of gene expression, epigenetic Supporting Evidence: PMID:11950982 these genes likely play a conserved role in repressing gene expression file:MAIZE/EZ1/EZ1-deep-research-falcon.md PRC2-mediated H3K27me3 participates in allele-specific repression and imprinting behavior in maize endosperm
GO:0009909 regulation of flower development	IEA GO_REF:0000107	KEEP AS NON CORE	Summary: IEA annotation transferred from the Arabidopsis ortholog (SWN/CLF) by Ensembl Compara. In Arabidopsis, E(z)/PRC2 represses floral regulators via H3K27me3; this is a pleiotropic developmental role rather than the core molecular function. Reason: Plausible by orthology and consistent with the well-known role of Arabidopsis E(z) homologs (CLF/SWN) in repressing flowering-pathway genes via H3K27me3, but it is a downstream, pleiotropic developmental consequence of PRC2 silencing rather than the gene's core biochemical function. No maize-specific flower-development phenotype was retrieved for MEZ1. Retain as a non-core developmental process. Supporting Evidence: file:MAIZE/EZ1/EZ1-deep-research-falcon.md braA.clf-1 mutants have reduced H3K27me3 at flowering integrator loci (FT, SOC1, SEP3 homologs) with increased transcript levels and accelerated flowering
GO:0031507 heterochromatin formation	IEA GO_REF:0000107	ACCEPT	Summary: IEA annotation (Ensembl ortholog transfer); duplicates the IBA annotation to the same term. Heterochromatin (facultative, H3K27me3) formation is a core process for the E(z)/PRC2 family. Reason: Correct and consistent with the IBA annotation to the same term. Plant PRC2 deposits H3K27me3 to establish facultative heterochromatin, and maize H3K27me3 marks define facultative heterochromatin attributed to the E(z)/PRC2 pathway. Duplicate annotations with different evidence codes are acceptable; this IEA provides additional computational support for a core process. Supporting Evidence: file:MAIZE/EZ1/EZ1-deep-research-falcon.md Genomic distribution of maize facultative heterochromatin marked by trimethylation of H3K27 file:MAIZE/EZ1/EZ1-deep-research-falcon.md PRC2 catalyzes H3K27 trimethylation (H3K27me3)
GO:0045814 negative regulation of gene expression, epigenetic	IEA GO_REF:0000107	ACCEPT	Summary: IEA annotation (Ensembl ortholog transfer). EZ1/MEZ1 mediates epigenetic gene silencing through H3K27 methylation. This accurately captures the directional, mechanism-specific biological role of PRC2. Reason: Accurate and informative. EZ1/MEZ1 deposits repressive H3K27 methylation leading to transcriptional repression of target genes (UniProt FUNCTION) and is a PRC2 catalytic subunit; PRC2 is the canonical machinery for epigenetic negative regulation of gene expression in plants. The term correctly captures the gene's directional repressive role and is preferable to the generic "regulation of DNA-templated transcription". Supporting Evidence: file:MAIZE/EZ1/EZ1-deep-research-falcon.md PRC2-mediated H3K27me3 participates in allele-specific repression and imprinting behavior in maize endosperm PMID:11950982 these genes likely play a conserved role in repressing gene expression
GO:0046976 histone H3K27 methyltransferase activity	IEA GO_REF:0000107	ACCEPT	Summary: IEA annotation (Ensembl ortholog transfer). This is the substrate-specific molecular function of EZ1/MEZ1 and a core annotation. Reason: Core molecular function, correctly specified. EZ1/MEZ1 is an E(z)-class enzyme that methylates Lys-27 of histone H3 (UniProt FUNCTION) and is a SAM-dependent histone lysine methyltransferase acting on H3K27 consistent with its EC assignment in UniProt and its E(z)-class SET domain conservation. This is the central activity of the gene product; accept. (The narrower trimethyltransferase term GO:0140951 is also present and likewise accepted.) Supporting Evidence: file:MAIZE/EZ1/EZ1-deep-research-falcon.md its expected enzymatic role is to use S-adenosylmethionine (SAM) to methylate histone H3 Lys-27, producing H3K27me3 on chromatin within PRC2 file:MAIZE/EZ1/EZ1-deep-research-falcon.md E(z)-family SET-domain proteins (e.g., CLF/SWN/MEA in Arabidopsis) as the catalytic subunits responsible for depositing H3K27me3
GO:0048586 regulation of long-day photoperiodism, flowering	IEA GO_REF:0000107	KEEP AS NON CORE	Summary: IEA annotation transferred from the Arabidopsis ortholog by Ensembl Compara (also reflected in the UniProt EnsemblPlants GO line). A pleiotropic, photoperiod-dependent developmental role inferred from orthology, not the core function. Reason: A plausible orthology-based developmental role: Arabidopsis E(z)/PRC2 represses flowering-time regulators (e.g. FLC/FT module) via H3K27me3, and photoperiod-dependent flowering is one downstream output. This is a pleiotropic, indirect developmental consequence of PRC2-mediated silencing rather than the gene's core biochemical function, and no maize-specific photoperiod phenotype was retrieved for MEZ1. Retain as non-core. Supporting Evidence: file:MAIZE/EZ1/EZ1-deep-research-falcon.md CLF as a “major H3K27 methyltransferase regulating flowering time” file:MAIZE/EZ1/EZ1-deep-research-falcon.md braA.clf-1 mutants have reduced H3K27me3 at flowering integrator loci (FT, SOC1, SEP3 homologs) with increased transcript levels and accelerated flowering

Core Functions

EZ1/MEZ1 is an Enhancer-of-zeste [E(z)]-class SET-domain histone-lysine N-methyltransferase (EC 2.1.1.356) that, as the catalytic subunit of plant Polycomb Repressive Complex 2 (PRC2), uses S-adenosyl-L-methionine to methylate Lys-27 of histone H3 (H3K27me1/2/3).

Molecular Function:

histone H3K27 methyltransferase activity

Supporting Evidence:

file:MAIZE/EZ1/EZ1-deep-research-falcon.md
its expected enzymatic role is to use S-adenosylmethionine (SAM) to methylate **histone H3 Lys-27**, producing H3K27me3 on chromatin within PRC2
file:MAIZE/EZ1/EZ1-deep-research-falcon.md
E(z)-family SET-domain proteins (e.g., **CLF/SWN/MEA** in Arabidopsis) as the catalytic subunits responsible for depositing H3K27me3

Through H3K27 methylation, EZ1/MEZ1 establishes a repressive chromatin state (facultative heterochromatin) at target loci, mediating epigenetic transcriptional repression as part of a nuclear PcG (PRC2) protein complex. Maize H3K27me3 marks define facultative heterochromatin attributed to the E(z)/PRC2 pathway and are strongly associated with developmental gene repression and imprinting.

Molecular Function:

histone H3K27 methyltransferase activity

Directly Involved In:

heterochromatin formation negative regulation of gene expression, epigenetic

Cellular Locations:

nucleus

In Complex:

PcG protein complex

Supporting Evidence:

file:MAIZE/EZ1/EZ1-deep-research-falcon.md
PRC2-dependent deposition of H3K27me3 is a chromatin-associated nuclear process
file:MAIZE/EZ1/EZ1-deep-research-falcon.md
Genomic distribution of maize facultative heterochromatin marked by trimethylation of H3K27
file:MAIZE/EZ1/EZ1-deep-research-falcon.md
PRC2-mediated H3K27me3 participates in **allele-specific repression** and imprinting behavior in maize endosperm
PMID:11950982
these genes likely play a conserved role in repressing gene expression

References

PMID:11950982

Sequence relationships, conserved domains, and expression patterns for maize homologs of the polycomb group genes E(z), esc, and E(Pc).

Primary maize reference (Springer et al. 2002) describing the three maize Enhancer-of-zeste-like genes Mez1/Mez2/Mez3 (Mez1 = EZ1/MEZ1), their conserved PcG domains, and tissue expression; Mez transcripts were detected in all tissues tested. PcG proteins act in developmental and epigenetic regulation of gene expression, and the cross-kingdom conservation of E(z)/esc homologs indicates a conserved role in repressing gene expression.

GO_REF:0000002

Gene Ontology annotation through association of InterPro records with GO terms

InterPro-to-GO mappings (IPR045318 EZH1/2-like) assign histone methyltransferase activity and chromatin remodeling to EZ1.

GO_REF:0000033

Annotation inferences using phylogenetic trees

E(z)/EZH-family functions (chromatin binding, heterochromatin formation) are conserved across the PANTHER PTHR45747 phylogenetic group and propagated to EZ1 by IBA.

GO_REF:0000043

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

SwissProt keyword-derived (SPKW) annotation present in the Sept 2025 goa_uniprot_gcrp snapshot but removed from the current GOA release after GOA retired the keyword2GO pipeline for cellular organisms.
For EZ1, the keyword "Methyltransferase"/"Transferase" mapped to the generic process "methylation" (GO:0032259), which drops the substrate; the substrate-specific histone H3K27 methyltransferase activity is already annotated, so the generic process term is redundant.

GO_REF:0000107

Automatic transfer of experimentally verified manual GO annotation data to orthologs using Ensembl Compara

Annotations transferred from the Arabidopsis (SWN/CLF) and rice E(z) orthologs to maize EZ1, including histone H3K27 methyltransferase activity, heterochromatin formation, epigenetic negative regulation, and developmental (flowering/photoperiod) processes.

GO_REF:0000120

Combined Automated Annotation using Multiple IEA Methods

Nuclear localization, PcG protein complex membership, and EC-derived histone H3K27 trimethyltransferase activity assigned to EZ1 by combined IEA methods.

file:MAIZE/EZ1/EZ1-deep-research-falcon.md

Deep-research report (falcon / Edison Scientific Literature) - functional annotation of maize EZ1/MEZ1 (Q8S4P6).

Confirms target identity: maize Mez1 is one of three E(z)-like genes (Mez1/Mez2/Mez3); Mez1 is the clf-like homolog while Mez2/Mez3 are EZA1/SWN-like (Springer et al. 2002, doi:10.1104/pp.010742), matching UniProt Q8S4P6 as an EZH1/2-like histone-lysine methyltransferase.
EZ1/MEZ1 is most strongly supported to be a SAM-dependent histone lysine methyltransferase acting on H3K27, consistent with its EC assignment in UniProt and its E(z)-class SET domain conservation; plant PRC2 deposits H3K27 methylation establishing a repressive chromatin state at target loci.
PRC2 is a chromatin-associated nuclear complex; most PRC2 proteins localize to the nucleus and form multi-subunit complexes, supporting EZ1/MEZ1 nuclear, on-chromatin function within PRC2-like assemblies.
Maize H3K27me3 marks define facultative heterochromatin attributed to the E(z)/PRC2 pathway; Mez2/Mez3 mutants reduce H3K27me3 at a subset of loci (partial redundancy); Mez1 is uniquely imprinted among the three homologs; direct Mez1 loss-of-function and in vitro biochemistry on the maize protein were not available in the retrieved corpus.

Suggested Experiments

Experiment: Generate maize mez1 (single) and mez1 mez2 mez3 (higher-order) loss-of-function alleles and profile genome-wide H3K27me3 by ChIP-seq across tissues (including endosperm) with matched RNA-seq, to define Mez1-dependent H3K27me3 domains and de-repressed target genes.

Hypothesis: Mez1 (the clf-like homolog) contributes non-redundantly to a subset of H3K27me3 domains not covered by Mez2/Mez3, including imprinted loci in endosperm.

Type: loss-of-function genetics with ChIP-seq/RNA-seq

Experiment: Reconstitute a maize PRC2 from recombinant MEZ1 plus maize FIE/MSI1/SU(Z)12-like subunits and assay SAM-dependent methyltransferase activity on recombinant nucleosomes, measuring methylation state at H3K27 by quantitative mass spectrometry.

Hypothesis: MEZ1 is catalytically active as an H3K27 methyltransferase only (or much more efficiently) within an assembled PRC2 complex, consistent with the conserved requirement of non-catalytic PRC2 subunits for activity.

Type: in vitro reconstituted histone methyltransferase assay

Experiment: Test MEZ1 substrate and residue specificity using SET-domain catalytic point mutants and a panel of histone H3 peptides/nucleosomes carrying K27 versus other lysine substrates, quantifying product methylation states.

Hypothesis: The conserved E(z) SET domain of MEZ1 confers strict H3K27 specificity, and catalytic-site mutations abolish methyltransferase activity without affecting PRC2 assembly.

Type: structure-function mutagenesis and enzyme specificity assay

Deep Research

Falcon

(EZ1-deep-research-falcon.md)

this with annotations you find in gene/protein databases, but these can be outdated or inaccurate. Falcon Edison Scientific Literature 23 citations 2 artifacts 2026-05-30T00:23:50.944941

Edison artifact artifact-00 (text/markdown)

## Context ID: pqac-00000018 The requested visual content was found in Figure 1, Table 1, and Figure 4. Figure 1 shows the overall genomic distribution of H3K27 (image/png)

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.

We are interested in where in or outside the cell the gene product carries out its function.

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: Maize EZ1 (UniProt Q8S4P6; gene synonyms: EZ1 / MEZ1)

0) Target verification (mandatory disambiguation)

The UniProt accession Q8S4P6 is specified as Histone-lysine N-methyltransferase EZ1 (Enhancer of zeste protein 1) from Zea mays. In maize primary literature, the canonical nomenclature for Enhancer-of-zeste homologs is Mez1/Mez2/Mez3 (Maize enhancer of zeste), where Mez1 corresponds to EZ1/MEZ1 (the imprinted E(z) homolog most similar to Arabidopsis CLF). The maize genome is explicitly stated to encode three E(z) homologs (Mez1, Mez2, Mez3). (makarevitch2013genomicdistributionof pages 2-3)

1) Key concepts and definitions (current understanding)

1.1 Polycomb Repressive Complex 2 (PRC2) and H3K27me3

Trimethylation of histone H3 at lysine 27 (H3K27me3) is a repressive chromatin modification associated with transcriptional repression and developmental regulation in plants. In the conserved Polycomb system, a subset of Polycomb group proteins forms PRC2, which catalyzes methylation at H3K27. (makarevitch2013genomicdistributionof pages 1-2, makarevitch2013genomicdistributionof pages 2-3)

In plants, the E(z)-group subunits are the histone methyltransferases of PRC2. Crop and model-plant literature consistently identifies E(z)-family SET-domain proteins (e.g., CLF/SWN/MEA in Arabidopsis) as the catalytic subunits responsible for depositing H3K27me3. (nugroho2023transcriptomicandepigenomic pages 1-2, pozaviejo2024brassicarapacurly pages 1-2)

1.2 Where EZ1/MEZ1 fits

In maize, Mez1/EZ1 is one of the three E(z) homologs (Mez1/Mez2/Mez3) that are the best-supported candidates to supply PRC2 catalytic activity for H3K27me3 deposition. Mez1 is distinctive in that it is imprinted and closely related to Arabidopsis CLF, whereas Mez2/Mez3 are highly similar paralogs related to SWN/MEA-like lineages. (makarevitch2013genomicdistributionof pages 2-3)

2) Functional annotation of maize EZ1/MEZ1

2.1 Primary biochemical function (reaction and substrate)

Most direct maize-specific statement available in retrieved full texts: PRC2 catalyzes H3K27 trimethylation (H3K27me3). (makarevitch2013genomicdistributionof pages 1-2)

Inference to EZ1/MEZ1 specifically in maize: Since Mez1 is an E(z)-family PRC2 catalytic homolog (by phylogeny and family assignment within maize E(z) genes), its expected enzymatic role is to use S-adenosylmethionine (SAM) to methylate histone H3 Lys-27, producing H3K27me3 on chromatin within PRC2. This is strongly supported at the family/complex level in plants and by maize genetic/epigenomic evidence that E(z) homolog mutations alter H3K27me3 at defined loci (shown for Mez2/Mez3; Mez1 mutants were not recovered in the 2013 study). (makarevitch2013genomicdistributionof pages 5-7, makarevitch2013genomicdistributionof pages 7-9, makarevitch2013genomicdistributionof pages 1-2)

Important limitation: The retrieved maize texts do not provide residue-level catalytic mechanisms, methylation-state preferences beyond trimethylation (me1/me2 vs me3), or explicit biochemical assays on purified ZmMEZ1; thus, substrate-state specificity cannot be stated from the retrieved corpus and should be treated as not directly evidenced here. (makarevitch2013genomicdistributionof pages 10-11, makarevitch2013genomicdistributionof pages 7-9)

2.2 Complex context (PRC2 membership in maize endosperm)

A maize endosperm study profiling H3K27me3 dynamics during grain filling reports that multiple PRC2 components are highly expressed around the onset of grain filling (En6D–En10D) including ZmFie1, ZmEmf2b, ZmMSI1c, and ZmMEZ1; the authors interpret this as evidence that a ZmFie1-mediated PRC2 is a primary regulator during this window. (wang2025thefie1prc2complex pages 3-4)

This places ZmMEZ1 (EZ1) in a cereal endosperm PRC2 module during a developmentally and agronomically important transition. (wang2025thefie1prc2complex pages 3-4)

3) Biological processes and pathways in maize (direct evidence emphasized)

3.1 Endosperm imprinting and allelic chromatin marking

A strong and quantitative maize finding is the association between H3K27me3 and imprinting in endosperm: nearly all maize paternally expressed genes (PEGs) examined (41/46) show H3K27me3 enrichment in endosperm, and in tested cases the mark is restricted to the silent maternal allele. This supports a pathway in which PRC2-mediated H3K27me3 participates in allele-specific repression and imprinting behavior in maize endosperm. (makarevitch2013genomicdistributionof pages 10-11, makarevitch2013genomicdistributionof pages 5-7)

Mez1 is explicitly described as the imprinted maize E(z) homolog, suggesting (by association) that Mez1/EZ1 is a plausible contributor to endosperm-specific Polycomb regulation (although direct Mez1 loss-of-function genetics were not available in the retrieved maize study). (makarevitch2013genomicdistributionof pages 10-11, makarevitch2013genomicdistributionof pages 2-3)

3.2 Genome-wide H3K27me3 landscape and dependence on maize E(z) homologs

Maize H3K27me3 is tissue-variable and enriched in gene-dense chromosome arms; endosperm is notably distinct in its set of marked genes. (makarevitch2013genomicdistributionof pages 2-3)

A key mechanistic result from maize genetics is that Mez2/Mez3 mutations reduce H3K27me3 at a subset of genomic loci. In seedlings, a genome-wide ChIP-chip analysis detected 4374 H3K27me3-enriched segments in B73; 742 (17%) were classified as Mez2/3-dependent (with segment categories showing differential dependence on mez2 vs mez3 vs double mutants). (makarevitch2013genomicdistributionof pages 7-9)

The table/figure evidence for these segment counts and dependence classes is shown directly in the paper’s tabulated/figure materials. (makarevitch2013genomicdistributionof media 76c36c18)

Despite these molecular changes, mez2/mez3 single and double mutants showed no striking morphological defects (slightly smaller but fertile), and RNA-seq did not show broad expression effects enriched among Mez2/3-dependent H3K27me3 targets, suggesting substantial redundancy and/or context specificity for visible phenotypes. (makarevitch2013genomicdistributionof pages 7-9, makarevitch2013genomicdistributionof pages 10-11)

3.3 Endosperm filling: developmental-stage PRC2 activity and quantitative epigenomics

During maize endosperm filling, CUT&Tag profiling of H3K27me3 across 6–20 DAP shows dynamic peak gains and losses around grain-filling onset. The study reports 8365 peaks gained (8 vs 6 DAP) and 12,111 peaks lost (12 vs 10 DAP); intersecting these yielded 5923 common peaks (FSPs) corresponding to 2838 genes, enriched for transcription-factor and nutrient reservoir functions. (wang2025thefie1prc2complex pages 3-4)

Expression evidence indicates ZmFie1 is endosperm-specific and increases after the coenocytic phase, while ZmFie2 is ubiquitous and high earlier (example FPKM values: En48HAP 12.98 vs En10D 2.46). ZmMEZ1 shows its highest expression in endosperm during 6–10 DAP alongside other PRC2 members. (wang2025thefie1prc2complex pages 3-4)

4) Subcellular localization

The maize studies retrieved here mainly imply localization via function: PRC2-dependent deposition of H3K27me3 is a chromatin-associated nuclear process. (makarevitch2013genomicdistributionof pages 1-2, wang2025thefie1prc2complex pages 3-4)

Direct experimental crop evidence for localization comes from a 2023 upland cotton PRC2 study, which reports that most PRC2 core proteins localize to the nucleus and physically interact to form multi-subunit complexes. This supports the expectation that maize PRC2 core subunits (including E(z)/MEZ family proteins) are nuclear/chromatin-associated. (cheng2023genomewideidentificationand pages 1-2)

5) Recent developments and latest research (prioritizing 2023–2024)

5.1 2023: crop PRC2 systems biology (Brassica rapa)

A 2023 Brassica rapa study combined transcriptomic and epigenomic profiling to show that PRC2 (via CLF, an E(z)-family catalytic subunit) regulates not only development but also stress-responsive metabolism (e.g., glucosinolate pathways). The study explicitly states CLF catalyzes H3K27me3 and notes that PRC2 complex subunits are required for nucleosome association of PRC2, framing how catalytic function is integrated with chromatin targeting. (nugroho2023transcriptomicandepigenomic pages 1-2, nugroho2023transcriptomicandepigenomic pages 2-3)

5.2 2023: crop PRC2 components, nuclear localization, and interactions (cotton)

A 2023 cotton PRC2 paper provides crop-level evidence for PRC2 conservation, classification into the four core groups (E(z), Su(z)12, ESC, p55/MSI), nuclear localization of components, and protein–protein interactions consistent with assembly into multi-subunit complexes—important context for interpreting maize PRC2/EZ1 behavior. (cheng2023genomewideidentificationand pages 1-2)

5.3 2024: crop PRC2 catalytic subunit as an agronomic lever (flowering time)

A 2024 Brassica rapa study presents CLF as a “major H3K27 methyltransferase regulating flowering time” and shows that braA.clf-1 mutants have reduced H3K27me3 at flowering integrator loci (FT, SOC1, SEP3 homologs) with increased transcript levels and accelerated flowering. It explicitly frames this mechanistic knowledge as enabling engineering of Brassica varieties with different flowering requirements. (pozaviejo2024brassicarapacurly pages 1-2)

5.4 2024: maize PcG pathway regulators affecting yield-relevant traits

A 2024 maize study identifies a plant-specific PcG factor ZmEMF1a (mn8) that interacts with PRC2 subunit ZmMSI1 and PRC1 component ZmRING1; its mutation causes genome-wide reductions in H3K27me3 and reduced kernel size and weight, tying Polycomb-mediated chromatin states to yield-relevant kernel traits. (zhou2024zmemf1aisrequired pages 1-5)

6) Current applications and real-world implementations

Direct evidence for deployed, field-scale applications is not described in the retrieved texts; however, multiple primary studies provide validated levers and phenotypic outputs with clear translational relevance.

6.1 Cereal grain quality/yield levers via PRC2-H3K27me3 control of storage proteins and proliferation

A cereals endosperm study links PRC2 (via FIE1-containing PRC2) to balancing endosperm cell proliferation and storage-protein gene regulation, and explicitly discusses the potential to “harness these modifications for crop improvement.” In maize, ZmFie1 knockout is reported to cause smaller kernels with increased zein accumulation and reduction of H3K27me3 on α-zein loci; related examples in rice and wheat connect PRC2-linked regulation to prolamin/gluten and kernel size traits. Although this is not a direct manipulation of ZmMEZ1, ZmMEZ1 is a PRC2 member expressed at the relevant developmental window, so it is mechanistically connected to the same PRC2-H3K27me3 axis. (wang2025thefie1prc2complex pages 1-2, wang2025thefie1prc2complex pages 12-14, wang2025thefie1prc2complex pages 3-4)

6.2 Flowering-time engineering in Brassica as a PRC2 paradigm

The Brassica rapa CLF work explicitly proposes that understanding PRC2/H3K27me3 control of flowering integrator genes could aid yield by engineering varieties with different flowering-time requirements, but notes pleiotropic effects (e.g., growth/leaf morphology) that would need to be managed. This provides a concrete example of how PRC2 catalytic subunits can be agricultural levers, relevant by analogy to maize PRC2/E(z) biology. (pozaviejo2024brassicarapacurly pages 1-2)

7) Expert analysis and interpretation (bounded by evidence)

Maize EZ1/MEZ1 is best understood as a PRC2 catalytic E(z)-family member with a likely specialized endosperm role, given (i) Mez1 imprinting and (ii) co-expression with a PRC2 module at grain-filling onset. (makarevitch2013genomicdistributionof pages 10-11, wang2025thefie1prc2complex pages 3-4)
Functional redundancy is a major theme in maize E(z) homologs, as mez2/mez3 mutations affect only a subset of H3K27me3 loci and show minimal obvious morphology, implying either compensation by Mez1 and/or other mechanisms that buffer loss of specific H3K27me3 peaks. (makarevitch2013genomicdistributionof pages 7-9, makarevitch2013genomicdistributionof pages 10-11)
Trait engineering via PRC2 must account for pleiotropy and epigenetic buffering: crop studies show uncoupling between transcript changes and final storage-protein accumulation in some contexts and pleiotropic developmental defects when core H3K27 writers are perturbed. (wang2025thefie1prc2complex pages 11-12, pozaviejo2024brassicarapacurly pages 1-2)

8) Key statistics and data points (selected)

Maize encodes three E(z) homologs: Mez1/Mez2/Mez3. (makarevitch2013genomicdistributionof pages 2-3)
Endosperm imprinting association: 41/46 PEGs marked by H3K27me3 in endosperm; maternal-allele restriction in tested cases. (makarevitch2013genomicdistributionof pages 10-11)
B73 seedling H3K27me3 segments: 4374 total; 742 (17%) Mez2/3-dependent segments. (makarevitch2013genomicdistributionof pages 7-9, makarevitch2013genomicdistributionof media 76c36c18)
Endosperm grain-filling H3K27me3 dynamics (6–20 DAP): 8365 peaks gained (8 vs 6 DAP), 12,111 lost (12 vs 10 DAP), overlap 5923 peaks mapping to 2838 genes; 7084 new peaks at 20 DAP. (wang2025thefie1prc2complex pages 3-4)
PRC2 component expression in maize endosperm: ZmFie2 example FPKM 12.98 (En48HAP) vs 2.46 (En10D); ZmMEZ1 among PRC2 members highest in endosperm during 6–10 DAP. (wang2025thefie1prc2complex pages 3-4)

9) Evidence summary table

The following table consolidates gene-level evidence and quantitative findings relevant to maize EZ1/MEZ1 functional annotation.

Gene/protein	Evidence type	Key findings	Quantitative data	Phenotypes	Source
Mez1 / EZ1 / ZmMEZ1	Expression, comparative genomics, epigenomic inference	One of three maize E(z) homologs in PRC2; imprinted and most closely related to Arabidopsis CLF; expressed in endosperm and other tested tissues; proposed to contribute to endosperm functions and H3K27me3 deposition as a PRC2 catalytic subunit by homology/inference. In developing endosperm, ZmMEZ1 is highly expressed together with ZmFie1, ZmEmf2b, ZmMSI1c, supporting participation in a grain-filling PRC2 complex.	H3K27me3 marks nearly all maize PEGs in endosperm: 41/46 (89%); in 3 tested cases the mark was maternal-allele restricted. During grain filling, intersecting dynamic peaks yielded 5923 common peaks (FSPs) mapping to 2838 genes; 7084 new H3K27me3 peaks were identified at 20 DAP.	No direct maize mez1 mutant phenotype reported in retrieved papers; no exon-insertion line recovered for Mez1 in the 2013 study. Functional role is strongest in endosperm/grain filling by expression-context evidence rather than direct genetics. (makarevitch2013genomicdistributionof pages 10-11, wang2025thefie1prc2complex pages 3-4)	Makarevitch et al., 2013, Plant Cell, https://doi.org/10.1105/tpc.112.106427, doi:10.1105/tpc.112.106427; Wang et al., 2025, Plant Communications, https://doi.org/10.1016/j.xplc.2025.101343, doi:10.1016/j.xplc.2025.101343
Mez2	Genetic, epigenomic, transcript, mutant analysis	Maize E(z) homolog and putative H3K27me3 methyltransferase; partially redundant with Mez3 for maintaining H3K27me3 at a subset of loci. Single and double mutant profiling shows only part of the maize H3K27me3 landscape depends on Mez2/3, indicating redundancy and additional methyltransferase activity from other E(z) family members.	In B73, 4374 H3K27me3-enriched segments were detected; 742 (17%) were Mez2/3-dependent, including 21 mez2-only, 315 mez3-only, 90 double-mutant-only, and 316 affected by either mutation; 659 filtered-gene-set genes lay in Mez2/3-dependent regions.	Homozygous mez2 single mutants and mez2 mez3 double mutants had no striking morphological defects; plants were somewhat smaller but fertile, and RNA-seq found no broad enrichment of expression changes among Mez2/3-dependent targets. (makarevitch2013genomicdistributionof pages 7-9, makarevitch2013genomicdistributionof pages 1-2, makarevitch2013genomicdistributionof media 76c36c18)	Makarevitch et al., 2013, Plant Cell, https://doi.org/10.1105/tpc.112.106427, doi:10.1105/tpc.112.106427
Mez3	Genetic, epigenomic, transcript, mutant analysis	Highly similar paralog of Mez2 (92% nucleotide identity) and more closely related to Arabidopsis SWN/MEA; contributes to H3K27me3 maintenance with stronger locus-specific impact than Mez2 in the reported mutant series. Supports the model that maize PRC2 catalytic activity is partitioned among multiple E(z)-like proteins.	Same mutant dataset as above: among the 742 Mez2/3-dependent H3K27me3 segments, 315 were mez3-only dependent versus 21 mez2-only, indicating a larger unique contribution from Mez3 in this dataset. Across tissues, H3K27me3-marked genes were highly dynamic: 40.6% marked in only one tissue, 21% in two tissues, and 8.2% in all five tissues.	mez3 mutants were viable and fertile with only mild size reduction; no major developmental abnormality reported despite local H3K27me3 losses. (makarevitch2013genomicdistributionof pages 2-3, makarevitch2013genomicdistributionof pages 7-9, makarevitch2013genomicdistributionof media 76c36c18)	Makarevitch et al., 2013, Plant Cell, https://doi.org/10.1105/tpc.112.106427, doi:10.1105/tpc.112.106427
Mez1/Mez2/Mez3 family (maize E(z) homologs)	Family-level comparative/epigenomic evidence	The maize genome encodes three E(z) homologs that are the likely catalytic PRC2 subunits responsible for histone H3 Lys-27 methylation, especially H3K27me3. Mez1 is the imprinted member; Mez2/Mez3 are paralogous SWN/MEA-like genes. Family-level evidence links these proteins to chromatin repression, imprinting, and developmental regulation in maize.	Genome-wide catalogs identified 6337 filtered H3K27me3-marked genes in at least one of five B73 tissues, 5690 in four diploid tissues, and 12,266 methylated genes overall. H3K27me3 covered 0.13%–1.91% of the genome depending on tissue, and ~16% of filtered-gene-set genes were marked in at least one tissue. Conservation statistics: 34% of maize H3K27me3 targets with Arabidopsis orthologs were also marked in Arabidopsis; conservation with rice was 64% for seedling-marked genes and 74% for genes marked in all five tissues.	Family-level mutant evidence indicates mild visible phenotypes for mez2/mez3, suggesting redundancy and/or context-specific importance; strongest biological association is with endosperm imprinting and grain-filling regulation. (makarevitch2013genomicdistributionof pages 2-3, makarevitch2013genomicdistributionof pages 5-7, makarevitch2013genomicdistributionof pages 1-2, makarevitch2013genomicdistributionof pages 20-23)	Makarevitch et al., 2013, Plant Cell, https://doi.org/10.1105/tpc.112.106427, doi:10.1105/tpc.112.106427
ZmMEZ1 within Fie1-PRC2 endosperm complex	Expression, developmental epigenomics	Recent cereal endosperm work places ZmMEZ1 in a maize PRC2 module with ZmFie1, ZmEmf2b, ZmMSI1c at the onset of grain filling; expression patterns suggest a ZmFie1-mediated PRC2 is the primary regulator during En6D–En10D, linking ZmMEZ1 to developmental H3K27me3 deposition during kernel filling.	Peak dynamics during endosperm development: 8365 peaks gained (8 vs 6 DAP), 12,111 peaks lost (12 vs 10 DAP), overlap 5923 peaks, corresponding to 2838 genes; additional gene sets included 1140 B8 gain-only and 3884 B12 loss-only genes.	Supports a role in balancing endosperm filling and development; phenotype in this excerpt is developmental-stage regulation rather than direct ZmMEZ1 mutant analysis. (wang2025thefie1prc2complex pages 3-4)	Wang et al., 2025, Plant Communications, https://doi.org/10.1016/j.xplc.2025.101343, doi:10.1016/j.xplc.2025.101343

Table: This table summarizes the strongest available evidence for maize Enhancer of zeste-like genes, especially Mez1/EZ1 and Mez2/Mez3, integrating genetic, epigenomic, and expression findings. It is useful for distinguishing direct maize evidence from family-level inference and for tracking the quantitative H3K27me3 data tied to each gene.

10) Visual evidence from primary maize literature

Quantitative classification of Mez2/3-dependent H3K27me3 segments and related figures/tables were retrieved from the 2013 Plant Cell study (e.g., Table listing Mez2/3-dependent vs independent segments; distribution and clustering in mez mutants). (makarevitch2013genomicdistributionof media 76c36c18, makarevitch2013genomicdistributionof media 80d49567, makarevitch2013genomicdistributionof media 8a1ba137)

11) Gaps and recommendations (explicit limitations)

Direct biochemical characterization of ZmMEZ1 (EZ1/MEZ1)—including enzymatic kinetics, methylation-state specificity (me1 vs me2 vs me3), and substrate peptide preferences—was not present in the retrieved full texts. Current statements therefore rely on complex-level PRC2 function and E(z)-family inference plus maize genetics for Mez2/Mez3. (makarevitch2013genomicdistributionof pages 10-11, makarevitch2013genomicdistributionof pages 7-9)
Direct ZmMEZ1 mutant phenotypes were not available in the retrieved maize genetics paper (no exon insertion line recovered), limiting causal assignment of specific H3K27me3 programs to Mez1 vs Mez2/Mez3. (makarevitch2013genomicdistributionof pages 10-11)

Key primary sources (with dates and URLs)

Makarevitch I. et al. 2013-03. Plant Cell “Genomic Distribution of Maize Facultative Heterochromatin Marked by Trimethylation of H3K27.” https://doi.org/10.1105/tpc.112.106427 (makarevitch2013genomicdistributionof pages 2-3)
Zhou Y. et al. 2024-10-01 (posted). Research Square preprint “ZmEMF1a is required for the maintainence of H2Aub and H3K27me3 modifications in maize kernel development.” https://doi.org/10.21203/rs.3.rs-4998315/v1 (zhou2024zmemf1aisrequired pages 1-5)
Cheng K. et al. 2023-02. BMC Plant Biology “Genome-wide identification and characterization of PRC2 core components in upland cotton.” https://doi.org/10.1186/s12870-023-04075-4 (cheng2023genomewideidentificationand pages 1-2)
Nugroho A.B.D. et al. 2023-02. Frontiers in Plant Science “Transcriptomic and epigenomic analyses… PRC2 regulates developmental and stress responsive metabolism in Brassica rapa.” https://doi.org/10.3389/fpls.2023.1079218 (nugroho2023transcriptomicandepigenomic pages 2-3)
Poza-Viejo L. et al. 2024-06. Planta “Brassica rapa CURLY LEAF is a major H3K27 methyltransferase regulating flowering time.” https://doi.org/10.1007/s00425-024-04454-7 (pozaviejo2024brassicarapacurly pages 1-2)
Wang J. et al. 2025-06-09. Plant Communications “The Fie1-PRC2 complex regulates H3K27me3 deposition to balance endosperm filling and development in cereals.” https://doi.org/10.1016/j.xplc.2025.101343 (wang2025thefie1prc2complex pages 3-4)

References

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(wang2025thefie1prc2complex pages 11-12): Jiechen Wang, Shuai Li, Liujie Wu, Dongsheng Shi, Lina Xu, Zhiping Zhang, Yongyan Wang, Chen Ji, Yuqi Chen, Xueling Zhou, Feifan Zhang, Mengyao Li, Xiaohan Li, Canghao Du, Qiong Wang, Xiaoduo Lu, Wenqin Wang, Guifeng Wang, and Yongrui Wu. The fie1-prc2 complex regulates h3k27me3 deposition to balance endosperm filling and development in cereals. Jun 2025. URL: https://doi.org/10.1016/j.xplc.2025.101343, doi:10.1016/j.xplc.2025.101343. This article has 2 citations and is from a peer-reviewed journal.
(makarevitch2013genomicdistributionof pages 20-23): Irina Makarevitch, Steven R. Eichten, Roman Briskine, Amanda J. Waters, Olga N. Danilevskaya, Robert B. Meeley, Chad L. Myers, Matthew W. Vaughn, and Nathan M. Springer. Genomic distribution of maize facultative heterochromatin marked by trimethylation of h3k27[w]. Plant Cell, 25:780-793, Mar 2013. URL: https://doi.org/10.1105/tpc.112.106427, doi:10.1105/tpc.112.106427. This article has 120 citations and is from a highest quality peer-reviewed journal.
(makarevitch2013genomicdistributionof media 80d49567): Irina Makarevitch, Steven R. Eichten, Roman Briskine, Amanda J. Waters, Olga N. Danilevskaya, Robert B. Meeley, Chad L. Myers, Matthew W. Vaughn, and Nathan M. Springer. Genomic distribution of maize facultative heterochromatin marked by trimethylation of h3k27[w]. Plant Cell, 25:780-793, Mar 2013. URL: https://doi.org/10.1105/tpc.112.106427, doi:10.1105/tpc.112.106427. This article has 120 citations and is from a highest quality peer-reviewed journal.
(makarevitch2013genomicdistributionof media 8a1ba137): Irina Makarevitch, Steven R. Eichten, Roman Briskine, Amanda J. Waters, Olga N. Danilevskaya, Robert B. Meeley, Chad L. Myers, Matthew W. Vaughn, and Nathan M. Springer. Genomic distribution of maize facultative heterochromatin marked by trimethylation of h3k27[w]. Plant Cell, 25:780-793, Mar 2013. URL: https://doi.org/10.1105/tpc.112.106427, doi:10.1105/tpc.112.106427. This article has 120 citations and is from a highest quality peer-reviewed journal.

Artifacts

Edison artifact artifact-00

Citations

makarevitch2013genomicdistributionof pages 2-3
makarevitch2013genomicdistributionof pages 1-2
makarevitch2013genomicdistributionof pages 7-9
cheng2023genomewideidentificationand pages 1-2
pozaviejo2024brassicarapacurly pages 1-2
makarevitch2013genomicdistributionof pages 10-11
nugroho2023transcriptomicandepigenomic pages 2-3
nugroho2023transcriptomicandepigenomic pages 1-2
makarevitch2013genomicdistributionof pages 5-7
makarevitch2013genomicdistributionof pages 20-23
w
https://doi.org/10.1105/tpc.112.106427,
https://doi.org/10.1016/j.xplc.2025.101343,
https://doi.org/10.1105/tpc.112.106427
https://doi.org/10.21203/rs.3.rs-4998315/v1
https://doi.org/10.1186/s12870-023-04075-4
https://doi.org/10.3389/fpls.2023.1079218
https://doi.org/10.1007/s00425-024-04454-7
https://doi.org/10.1016/j.xplc.2025.101343
https://doi.org/10.3389/fpls.2023.1079218,
https://doi.org/10.1007/s00425-024-04454-7,
https://doi.org/10.1186/s12870-023-04075-4,
https://doi.org/10.21203/rs.3.rs-4998315/v1,

📄 View Raw YAML

id: Q8S4P6
gene_symbol: EZ1
product_type: PROTEIN
status: COMPLETE
taxon:
  id: NCBITaxon:4577
  label: Zea mays
description: >
  Maize EZ1 (Q8S4P6), also known as MEZ1 (Maize Enhancer-of-zeste 1), is an
  Enhancer-of-zeste [E(z)]-class SET-domain histone-lysine N-methyltransferase
  (EC 2.1.1.356) and the catalytic-subunit candidate of plant Polycomb Repressive
  Complex 2 (PRC2). It is one of three maize E(z)-like genes (Mez1/Mez2/Mez3);
  phylogenetically Mez1 is the maize CLF-like (CURLY LEAF-like) homolog, whereas
  Mez2/Mez3 are EZA1/SWN-like (SWINGER-like) (Springer et al. 2002,
  doi:10.1104/pp.010742). The UniProt FUNCTION statement describes it as a Polycomb
  group protein and "Catalytic subunit of some PcG multiprotein complex, which
  methylates 'Lys-27' of histone H3, leading to transcriptional repression of the
  affected target genes". The enzyme uses S-adenosyl-L-methionine to transfer methyl
  groups onto Lys-27 of histone H3 (H3K27me1/2/3), establishing a repressive
  chromatin state (facultative heterochromatin) at target loci; in plants PRC2 is
  defined by this H3K27 methylation activity. The protein carries the canonical
  E(z)-family architecture (EZD1/EZD2, SANT, a Cys-rich CXC region, and the
  C-terminal SET domain "predicted to be involved in protein methylation") and acts
  in the nucleus on chromatin within PRC2-like assemblies that include maize
  homologs of FIE/MSI1/SU(Z)12-like proteins. As part of plant PRC2, MEZ1 functions
  in epigenetic gene silencing and developmental regulation (flowering, photoperiod
  response) and is notable as the only one of the three maize E(z) homologs that is
  imprinted, consistent with the strong association of maize H3K27me3 with imprinted
  (paternally expressed) genes in endosperm. Direct maize loss-of-function genetics
  exist for Mez2/Mez3 (whose mutants reduce H3K27me3 at a subset of loci, implying
  partial redundancy); a Mez1-specific knockout and in vitro biochemistry on the
  maize protein itself were not available in the retrieved literature, so the
  catalytic and complex-membership annotations rest on strong sequence/domain,
  phylogenetic, and orthology evidence plus the conserved plant PRC2 mechanism.
existing_annotations:
# --- SPKW keyword-mapping annotation (GO_REF:0000043) ---
# Present in the Sept 2025 goa_uniprot_gcrp snapshot (go-db plant.ddb); REMOVED
# from the current (2026) GOA release when GOA retired the keyword2GO pipeline
# for cellular organisms. Reviewed retrospectively to assess whether removal was
# justified. This is the SPKW-unique annotation derived from the "Methyltransferase"
# / "Transferase" UniProt keywords.
- term:
    id: GO:0032259
    label: methylation
  evidence_type: IEA
  original_reference_id: GO_REF:0000043
  retired: true
  qualifier: involved_in
  review:
    summary: >
      SPKW (GO_REF:0000043) annotation derived from the UniProt keyword
      "Methyltransferase"/"Transferase"; snapshot-only, removed in the current GOA
      release. EZ1/MEZ1 is genuinely a methyltransferase, but "methylation" is the
      generic process term that drops the substrate: the enzyme specifically performs
      histone H3 Lys-27 methylation.
    action: MARK_AS_OVER_ANNOTATED
    reason: >
      GOA's removal of this annotation was JUSTIFIED. The keyword-derived term
      "methylation" (GO:0032259) is the high-level parent process that simply states a
      methyl group is transferred, dropping all substrate specificity. EZ1/MEZ1 is an
      E(z)-class enzyme whose UniProt FUNCTION explicitly states it "methylates
      'Lys-27' of histone H3", i.e. it performs substrate-specific histone H3K27
      methylation as a SAM-dependent histone lysine methyltransferase acting on H3K27.
      The substrate specificity is already captured by the molecular-function terms
      retained in current GOA - "histone H3K27 methyltransferase activity"
      (GO:0046976) and "histone H3K27 trimethyltransferase activity" (GO:0140951) -
      and the biological role is captured by "heterochromatin formation" (GO:0031507)
      and "negative regulation of gene expression, epigenetic" (GO:0045814). The bare
      "methylation" process term therefore adds no information once these specific
      annotations are present. It cannot be usefully MODIFIED to a specific
      histone-methylation process term either, because the candidate substrate-specific
      process terms in GO ("histone H3-K27 methylation" GO:0070734 and "histone
      methylation" GO:0016571) are now obsolete - GO carries the substrate specificity
      on the molecular-function branch rather than as a dedicated process. Removal of
      the redundant generic keyword-derived term is appropriate (over-annotation).
    supported_by:
    - reference_id: file:MAIZE/EZ1/EZ1-deep-research-falcon.md
      supporting_text: its expected enzymatic role is to use S-adenosylmethionine
        (SAM) to methylate **histone H3 Lys-27**, producing H3K27me3 on chromatin
        within PRC2
    - reference_id: file:MAIZE/EZ1/EZ1-deep-research-falcon.md
      supporting_text: PRC2 catalyzes **H3K27 trimethylation (H3K27me3)**
# --- Current GOA annotations (2026 release) ---
- term:
    id: GO:0003682
    label: chromatin binding
  evidence_type: IBA
  original_reference_id: GO_REF:0000033
  qualifier: enables
  review:
    summary: >
      IBA annotation propagated across the E(z)/EZH phylogenetic group. As a PRC2
      catalytic subunit, EZ1/MEZ1 associates with chromatin (nucleosomes) to deposit
      H3K27 methylation.
    action: ACCEPT
    reason: >
      Appropriate and well supported by conserved biology. PRC2 is a chromatin-associated
      nuclear complex that deposits histone methylation on nucleosomes at genomic loci,
      so chromatin binding is a genuine, conserved molecular activity of the E(z)/EZH
      family. The IBA term is at the right level of specificity and consistent with the
      EZ1 SANT and CXC chromatin-engaging modules described for the maize MEZ proteins.
    supported_by:
    - reference_id: file:MAIZE/EZ1/EZ1-deep-research-falcon.md
      supporting_text: PRC2-dependent deposition of H3K27me3 is a chromatin-associated
        nuclear process
    - reference_id: file:MAIZE/EZ1/EZ1-deep-research-falcon.md
      supporting_text: PRC2 complex subunits are required for nucleosome association
        of PRC2
- term:
    id: GO:0031507
    label: heterochromatin formation
  evidence_type: IBA
  original_reference_id: GO_REF:0000033
  qualifier: involved_in
  review:
    summary: >
      IBA annotation: the E(z)/PRC2 family establishes repressive (facultative
      heterochromatin) chromatin states via H3K27me3. This is a core biological process
      of EZ1/MEZ1.
    action: ACCEPT
    reason: >
      Core function, strongly supported by conserved plant PRC2 biology and maize-specific
      epigenomics. Plant PRC2 deposits H3K27 methylation that establishes a repressive
      chromatin state at target loci, and maize H3K27me3 marks define facultative
      heterochromatin and are attributed to the E(z)/PRC2 pathway. The IBA term is at an
      appropriate level of specificity for an E(z)-class catalytic subunit.
    supported_by:
    - reference_id: file:MAIZE/EZ1/EZ1-deep-research-falcon.md
      supporting_text: Genomic distribution of maize facultative heterochromatin
        marked by trimethylation of H3K27
    - reference_id: file:MAIZE/EZ1/EZ1-deep-research-falcon.md
      supporting_text: Maize H3K27me3 is tissue-variable and enriched in gene-dense
        chromosome arms
- term:
    id: GO:0005634
    label: nucleus
  evidence_type: IEA
  original_reference_id: GO_REF:0000120
  qualifier: located_in
  review:
    summary: >
      IEA annotation for nuclear localization, consistent with the UniProt subcellular
      location ("Nucleus") and with PRC2 being a chromatin-associated nuclear complex.
    action: ACCEPT
    reason: >
      Correct and well supported. The UniProt entry assigns subcellular location
      "Nucleus", and PRC2 is inherently a chromatin-associated nuclear complex because it
      deposits histone methylation on nucleosomes; genome-wide analyses report that most
      PRC2 proteins localize to the nucleus. Although maize-specific localization
      microscopy for MEZ1 was not retrieved, the conservative inference is strong.
    supported_by:
    - reference_id: file:MAIZE/EZ1/EZ1-deep-research-falcon.md
      supporting_text: most PRC2 core proteins localize to the **nucleus** and physically
        interact to form multi-subunit complexes
    - reference_id: file:MAIZE/EZ1/EZ1-deep-research-falcon.md
      supporting_text: maize PRC2 core subunits (including E(z)/MEZ family proteins)
        are nuclear/chromatin-associated
- term:
    id: GO:0006338
    label: chromatin remodeling
  evidence_type: IEA
  original_reference_id: GO_REF:0000002
  qualifier: involved_in
  review:
    summary: >
      IEA annotation from InterPro (IPR045318, EZH1/2-like). "Chromatin remodeling" is
      an imprecise process term for a histone methyltransferase whose action is covalent
      H3K27 methylation, not ATP-dependent nucleosome repositioning.
    action: MODIFY
    reason: >
      The essence (EZ1 alters chromatin state) is correct, but "chromatin remodeling"
      (GO:0006338) conventionally denotes dynamic, often ATP-dependent reorganization of
      nucleosome structure, whereas EZ1/MEZ1 acts by depositing a covalent histone mark
      (H3K27 methylation) to establish a repressive chromatin state. The biology is more
      precisely captured by "heterochromatin formation" (GO:0031507), which is the
      established process for E(z)/PRC2-mediated H3K27me3 silencing and is already present
      via the IBA annotation. Modify to the more specific and accurate process term.
    proposed_replacement_terms:
    - id: GO:0031507
      label: heterochromatin formation
    supported_by:
    - reference_id: file:MAIZE/EZ1/EZ1-deep-research-falcon.md
      supporting_text: PRC2 catalyzes **H3K27 trimethylation (H3K27me3)**
    - reference_id: file:MAIZE/EZ1/EZ1-deep-research-falcon.md
      supporting_text: Genomic distribution of maize facultative heterochromatin
        marked by trimethylation of H3K27
- term:
    id: GO:0031519
    label: PcG protein complex
  evidence_type: IEA
  original_reference_id: GO_REF:0000120
  qualifier: part_of
  review:
    summary: >
      IEA annotation: EZ1/MEZ1 is part of a Polycomb group (PcG) protein complex (PRC2).
      This is a core cellular-component annotation for an E(z)-class catalytic subunit.
    action: ACCEPT
    reason: >
      Correct and core. The UniProt FUNCTION states EZ1 is a Polycomb group protein and
      the catalytic subunit of "some PcG multiprotein complex"; plant E(z)-class proteins
      function within PRC2-like assemblies that include FIE/MSI1/SU(Z)12-like subunits.
      In maize, EZ1/MEZ1 is most plausibly functional as part of PRC2-like complexes. The
      term is at an appropriate level of specificity for complex membership.
    supported_by:
    - reference_id: file:MAIZE/EZ1/EZ1-deep-research-falcon.md
      supporting_text: '**ZmMEZ1** is highly expressed together with **ZmFie1, ZmEmf2b,
        ZmMSI1c**, supporting participation in a grain-filling PRC2 complex'
    - reference_id: PMID:11950982
      supporting_text: Polycomb group (PcG) proteins play an important role in developmental
        and
- term:
    id: GO:0042054
    label: histone methyltransferase activity
  evidence_type: IEA
  original_reference_id: GO_REF:0000002
  qualifier: enables
  review:
    summary: >
      IEA annotation from InterPro (IPR045318, EZH1/2-like). EZ1/MEZ1 is a histone
      methyltransferase, but the substrate-specific child term "histone H3K27
      methyltransferase activity" (GO:0046976) is more informative and is already present.
    action: MODIFY
    reason: >
      The annotation is correct but too general. EZ1/MEZ1 is an E(z)-class enzyme that
      specifically methylates Lys-27 of histone H3; the deep research concludes it is a
      SAM-dependent histone lysine methyltransferase acting on H3K27, consistent with its
      EC assignment in UniProt (EC 2.1.1.356) and its E(z)-class SET domain conservation.
      The generic "histone methyltransferase activity" should be modified to the
      substrate-specific "histone H3K27 methyltransferase activity" (GO:0046976), which is
      already annotated (IBA/IEA) and captures the true catalytic specificity.
    proposed_replacement_terms:
    - id: GO:0046976
      label: histone H3K27 methyltransferase activity
    supported_by:
    - reference_id: file:MAIZE/EZ1/EZ1-deep-research-falcon.md
      supporting_text: its expected enzymatic role is to use S-adenosylmethionine
        (SAM) to methylate **histone H3 Lys-27**, producing H3K27me3 on chromatin
        within PRC2
    - reference_id: file:MAIZE/EZ1/EZ1-deep-research-falcon.md
      supporting_text: E(z)-family SET-domain proteins (e.g., **CLF/SWN/MEA** in Arabidopsis)
        as the catalytic subunits responsible for depositing H3K27me3
- term:
    id: GO:0140951
    label: histone H3K27 trimethyltransferase activity
  evidence_type: IEA
  original_reference_id: GO_REF:0000120
  qualifier: enables
  review:
    summary: >
      IEA annotation transferred from EC 2.1.1.356 (UniProtKB-EC). This is the most
      specific molecular-function term and matches the UniProt catalytic activity
      (formation of H3K27me3).
    action: ACCEPT
    reason: >
      Correct and maximally specific. The UniProt CATALYTIC ACTIVITY record assigns
      EC 2.1.1.356 (L-lysyl(27)-[histone H3] + 3 SAM -> trimethyl-L-lysyl(27)-[histone H3]),
      i.e. histone H3K27 trimethyltransferase activity, and the deep research confirms EZ1
      is a SAM-dependent histone lysine methyltransferase acting on H3K27 consistent with
      its EC assignment in UniProt. This is a core molecular function; accept as-is.
    supported_by:
    - reference_id: file:MAIZE/EZ1/EZ1-deep-research-falcon.md
      supporting_text: PRC2 catalyzes **H3K27 trimethylation (H3K27me3)**
    - reference_id: file:MAIZE/EZ1/EZ1-deep-research-falcon.md
      supporting_text: its expected enzymatic role is to use S-adenosylmethionine
        (SAM) to methylate **histone H3 Lys-27**, producing H3K27me3 on chromatin
        within PRC2
- term:
    id: GO:0001222
    label: transcription corepressor binding
  evidence_type: IEA
  original_reference_id: GO_REF:0000107
  qualifier: enables
  review:
    summary: >
      IEA annotation transferred from the Arabidopsis ortholog (AT2G23380 = SWN, P93831)
      by Ensembl Compara. "Transcription corepressor binding" is a non-specific
      protein-binding term with no maize-specific support and is not part of the gene's
      core methyltransferase function.
    action: MARK_AS_OVER_ANNOTATED
    reason: >
      This is an orthology-transferred protein-binding annotation lacking gene-specific
      support in maize. The retrieved literature does not identify a specific corepressor
      partner of EZ1/MEZ1; the gene's well-supported molecular function is its E(z)-class
      H3K27 methyltransferase activity within PRC2. "Protein binding"-type terms that do
      not identify an informative interaction partner are discouraged and add little once
      the catalytic MF and PcG-complex membership are annotated. Treat as an over-annotation
      pending direct interaction evidence.
    supported_by:
    - reference_id: file:MAIZE/EZ1/EZ1-deep-research-falcon.md
      supporting_text: E(z)-family SET-domain proteins (e.g., **CLF/SWN/MEA** in Arabidopsis)
        as the catalytic subunits responsible for depositing H3K27me3
- term:
    id: GO:0003727
    label: single-stranded RNA binding
  evidence_type: IEA
  original_reference_id: GO_REF:0000107
  qualifier: enables
  review:
    summary: >
      IEA annotation transferred from the Arabidopsis ortholog (AT2G23380 = SWN) by
      Ensembl Compara. There is no maize-specific evidence that EZ1/MEZ1 binds
      single-stranded RNA, and this is not part of its supported function.
    action: REMOVE
    reason: >
      Unsupported orthology transfer. While PRC2 RNA association has been reported in some
      systems, it is mechanistically contested and there is no maize-specific evidence that
      EZ1/MEZ1 binds single-stranded RNA. The retrieved literature characterizes EZ1/MEZ1
      strictly as a chromatin-associated, nuclear E(z)-class histone methyltransferase
      acting on H3K27; no RNA-binding assay supports this term for the maize protein. A
      speculative, ortholog-transferred ssRNA-binding MF that is not part of the gene's
      demonstrated function should be removed.
    supported_by:
    - reference_id: file:MAIZE/EZ1/EZ1-deep-research-falcon.md
      supporting_text: PRC2-dependent deposition of H3K27me3 is a chromatin-associated
        nuclear process
- term:
    id: GO:0005677
    label: chromatin silencing complex
  evidence_type: IEA
  original_reference_id: GO_REF:0000107
  qualifier: part_of
  review:
    summary: >
      IEA annotation (Ensembl ortholog transfer; also present via EnsemblPlants in the
      UniProt record). EZ1/MEZ1 is part of a PRC2 chromatin-silencing complex that
      establishes repressive H3K27me3 chromatin.
    action: ACCEPT
    reason: >
      Consistent with the gene's role. Plant PRC2 is a chromatin-silencing complex that
      deposits H3K27 methylation to establish a repressive chromatin state at target loci,
      mediating transcriptional repression; EZ1/MEZ1 is the catalytic subunit of such a
      PcG complex per UniProt. This complex-membership term is appropriate and overlaps with
      the PcG protein complex annotation.
    supported_by:
    - reference_id: file:MAIZE/EZ1/EZ1-deep-research-falcon.md
      supporting_text: classification into the four core groups (E(z), Su(z)12, ESC,
        p55/MSI), nuclear localization of components
    - reference_id: PMID:11950982
      supporting_text: these genes likely play a conserved role in repressing gene
        expression
- term:
    id: GO:0006355
    label: regulation of DNA-templated transcription
  evidence_type: IEA
  original_reference_id: GO_REF:0000107
  qualifier: involved_in
  review:
    summary: >
      IEA annotation (Ensembl ortholog transfer). EZ1/MEZ1 regulates transcription, but
      this is a very generic process term; its action is specifically epigenetic
      transcriptional repression.
    action: MODIFY
    reason: >
      The essence is correct (EZ1 affects transcription) but the term is overly general.
      EZ1/MEZ1 acts by depositing repressive H3K27 methylation leading to transcriptional
      repression of target genes (UniProt FUNCTION), i.e. it mediates epigenetic
      negative regulation of gene expression. The more specific and informative term
      "negative regulation of gene expression, epigenetic" (GO:0045814) - which is already
      present as a separate IEA annotation - better captures this directional, mechanism-
      specific role. Modify the generic transcription-regulation term to the epigenetic
      negative-regulation term.
    proposed_replacement_terms:
    - id: GO:0045814
      label: negative regulation of gene expression, epigenetic
    supported_by:
    - reference_id: PMID:11950982
      supporting_text: these genes likely play a conserved role in repressing gene
        expression
    - reference_id: file:MAIZE/EZ1/EZ1-deep-research-falcon.md
      supporting_text: PRC2-mediated H3K27me3 participates in **allele-specific repression**
        and imprinting behavior in maize endosperm
- term:
    id: GO:0009909
    label: regulation of flower development
  evidence_type: IEA
  original_reference_id: GO_REF:0000107
  qualifier: involved_in
  review:
    summary: >
      IEA annotation transferred from the Arabidopsis ortholog (SWN/CLF) by Ensembl
      Compara. In Arabidopsis, E(z)/PRC2 represses floral regulators via H3K27me3; this is
      a pleiotropic developmental role rather than the core molecular function.
    action: KEEP_AS_NON_CORE
    reason: >
      Plausible by orthology and consistent with the well-known role of Arabidopsis E(z)
      homologs (CLF/SWN) in repressing flowering-pathway genes via H3K27me3, but it is a
      downstream, pleiotropic developmental consequence of PRC2 silencing rather than the
      gene's core biochemical function. No maize-specific flower-development phenotype was
      retrieved for MEZ1. Retain as a non-core developmental process.
    supported_by:
    - reference_id: file:MAIZE/EZ1/EZ1-deep-research-falcon.md
      supporting_text: braA.clf-1 mutants have reduced H3K27me3 at flowering integrator
        loci (FT, SOC1, SEP3 homologs) with increased transcript levels and accelerated
        flowering
- term:
    id: GO:0031507
    label: heterochromatin formation
  evidence_type: IEA
  original_reference_id: GO_REF:0000107
  qualifier: involved_in
  review:
    summary: >
      IEA annotation (Ensembl ortholog transfer); duplicates the IBA annotation to the
      same term. Heterochromatin (facultative, H3K27me3) formation is a core process for
      the E(z)/PRC2 family.
    action: ACCEPT
    reason: >
      Correct and consistent with the IBA annotation to the same term. Plant PRC2 deposits
      H3K27me3 to establish facultative heterochromatin, and maize H3K27me3 marks define
      facultative heterochromatin attributed to the E(z)/PRC2 pathway. Duplicate annotations
      with different evidence codes are acceptable; this IEA provides additional
      computational support for a core process.
    supported_by:
    - reference_id: file:MAIZE/EZ1/EZ1-deep-research-falcon.md
      supporting_text: Genomic distribution of maize facultative heterochromatin
        marked by trimethylation of H3K27
    - reference_id: file:MAIZE/EZ1/EZ1-deep-research-falcon.md
      supporting_text: PRC2 catalyzes **H3K27 trimethylation (H3K27me3)**
- term:
    id: GO:0045814
    label: negative regulation of gene expression, epigenetic
  evidence_type: IEA
  original_reference_id: GO_REF:0000107
  qualifier: involved_in
  review:
    summary: >
      IEA annotation (Ensembl ortholog transfer). EZ1/MEZ1 mediates epigenetic gene
      silencing through H3K27 methylation. This accurately captures the directional,
      mechanism-specific biological role of PRC2.
    action: ACCEPT
    reason: >
      Accurate and informative. EZ1/MEZ1 deposits repressive H3K27 methylation leading to
      transcriptional repression of target genes (UniProt FUNCTION) and is a PRC2 catalytic
      subunit; PRC2 is the canonical machinery for epigenetic negative regulation of gene
      expression in plants. The term correctly captures the gene's directional repressive
      role and is preferable to the generic "regulation of DNA-templated transcription".
    supported_by:
    - reference_id: file:MAIZE/EZ1/EZ1-deep-research-falcon.md
      supporting_text: PRC2-mediated H3K27me3 participates in **allele-specific repression**
        and imprinting behavior in maize endosperm
    - reference_id: PMID:11950982
      supporting_text: these genes likely play a conserved role in repressing gene
        expression
- term:
    id: GO:0046976
    label: histone H3K27 methyltransferase activity
  evidence_type: IEA
  original_reference_id: GO_REF:0000107
  qualifier: enables
  review:
    summary: >
      IEA annotation (Ensembl ortholog transfer). This is the substrate-specific
      molecular function of EZ1/MEZ1 and a core annotation.
    action: ACCEPT
    reason: >
      Core molecular function, correctly specified. EZ1/MEZ1 is an E(z)-class enzyme that
      methylates Lys-27 of histone H3 (UniProt FUNCTION) and is a SAM-dependent histone
      lysine methyltransferase acting on H3K27 consistent with its EC assignment in UniProt
      and its E(z)-class SET domain conservation. This is the central activity of the gene
      product; accept. (The narrower trimethyltransferase term GO:0140951 is also present
      and likewise accepted.)
    supported_by:
    - reference_id: file:MAIZE/EZ1/EZ1-deep-research-falcon.md
      supporting_text: its expected enzymatic role is to use S-adenosylmethionine
        (SAM) to methylate **histone H3 Lys-27**, producing H3K27me3 on chromatin
        within PRC2
    - reference_id: file:MAIZE/EZ1/EZ1-deep-research-falcon.md
      supporting_text: E(z)-family SET-domain proteins (e.g., **CLF/SWN/MEA** in Arabidopsis)
        as the catalytic subunits responsible for depositing H3K27me3
- term:
    id: GO:0048586
    label: regulation of long-day photoperiodism, flowering
  evidence_type: IEA
  original_reference_id: GO_REF:0000107
  qualifier: involved_in
  review:
    summary: >
      IEA annotation transferred from the Arabidopsis ortholog by Ensembl Compara (also
      reflected in the UniProt EnsemblPlants GO line). A pleiotropic, photoperiod-dependent
      developmental role inferred from orthology, not the core function.
    action: KEEP_AS_NON_CORE
    reason: >
      A plausible orthology-based developmental role: Arabidopsis E(z)/PRC2 represses
      flowering-time regulators (e.g. FLC/FT module) via H3K27me3, and photoperiod-dependent
      flowering is one downstream output. This is a pleiotropic, indirect developmental
      consequence of PRC2-mediated silencing rather than the gene's core biochemical
      function, and no maize-specific photoperiod phenotype was retrieved for MEZ1. Retain
      as non-core.
    supported_by:
    - reference_id: file:MAIZE/EZ1/EZ1-deep-research-falcon.md
      supporting_text: CLF as a “major H3K27 methyltransferase regulating flowering
        time”
    - reference_id: file:MAIZE/EZ1/EZ1-deep-research-falcon.md
      supporting_text: braA.clf-1 mutants have reduced H3K27me3 at flowering integrator
        loci (FT, SOC1, SEP3 homologs) with increased transcript levels and accelerated
        flowering
core_functions:
- description: >
    EZ1/MEZ1 is an Enhancer-of-zeste [E(z)]-class SET-domain histone-lysine
    N-methyltransferase (EC 2.1.1.356) that, as the catalytic subunit of plant
    Polycomb Repressive Complex 2 (PRC2), uses S-adenosyl-L-methionine to methylate
    Lys-27 of histone H3 (H3K27me1/2/3).
  molecular_function:
    id: GO:0046976
    label: histone H3K27 methyltransferase activity
  supported_by:
  - reference_id: file:MAIZE/EZ1/EZ1-deep-research-falcon.md
    supporting_text: its expected enzymatic role is to use S-adenosylmethionine (SAM)
      to methylate **histone H3 Lys-27**, producing H3K27me3 on chromatin within PRC2
  - reference_id: file:MAIZE/EZ1/EZ1-deep-research-falcon.md
    supporting_text: E(z)-family SET-domain proteins (e.g., **CLF/SWN/MEA** in Arabidopsis)
      as the catalytic subunits responsible for depositing H3K27me3
- description: >
    Through H3K27 methylation, EZ1/MEZ1 establishes a repressive chromatin state
    (facultative heterochromatin) at target loci, mediating epigenetic transcriptional
    repression as part of a nuclear PcG (PRC2) protein complex. Maize H3K27me3 marks
    define facultative heterochromatin attributed to the E(z)/PRC2 pathway and are
    strongly associated with developmental gene repression and imprinting.
  molecular_function:
    id: GO:0046976
    label: histone H3K27 methyltransferase activity
  directly_involved_in:
  - id: GO:0031507
    label: heterochromatin formation
  - id: GO:0045814
    label: negative regulation of gene expression, epigenetic
  locations:
  - id: GO:0005634
    label: nucleus
  in_complex:
    id: GO:0031519
    label: PcG protein complex
  supported_by:
  - reference_id: file:MAIZE/EZ1/EZ1-deep-research-falcon.md
    supporting_text: PRC2-dependent deposition of H3K27me3 is a chromatin-associated
      nuclear process
  - reference_id: file:MAIZE/EZ1/EZ1-deep-research-falcon.md
    supporting_text: Genomic distribution of maize facultative heterochromatin marked
      by trimethylation of H3K27
  - reference_id: file:MAIZE/EZ1/EZ1-deep-research-falcon.md
    supporting_text: PRC2-mediated H3K27me3 participates in **allele-specific repression**
      and imprinting behavior in maize endosperm
  - reference_id: PMID:11950982
    supporting_text: these genes likely play a conserved role in repressing gene expression
proposed_new_terms: []
suggested_questions:
- question: >
    Does purified maize MEZ1 (EZ1) have intrinsic H3K27 methyltransferase activity in a
    reconstituted maize PRC2, and what is its product specificity (mono/di/tri-methyl) at
    H3K27?
  experts:
  - Nathan M. Springer
- question: >
    What is the division of labor between the three maize E(z) homologs (Mez1/clf-like vs
    Mez2/Mez3/SWN-like) in establishing H3K27me3 at distinct genomic loci, and is Mez1
    uniquely required at imprinted/endosperm loci given that it is the only imprinted
    homolog?
  experts:
  - Nathan M. Springer
  - Irina Makarevitch
suggested_experiments:
- description: >
    Generate maize mez1 (single) and mez1 mez2 mez3 (higher-order) loss-of-function alleles
    and profile genome-wide H3K27me3 by ChIP-seq across tissues (including endosperm) with
    matched RNA-seq, to define Mez1-dependent H3K27me3 domains and de-repressed target genes.
  hypothesis: >
    Mez1 (the clf-like homolog) contributes non-redundantly to a subset of H3K27me3 domains
    not covered by Mez2/Mez3, including imprinted loci in endosperm.
  experiment_type: loss-of-function genetics with ChIP-seq/RNA-seq
- description: >
    Reconstitute a maize PRC2 from recombinant MEZ1 plus maize FIE/MSI1/SU(Z)12-like
    subunits and assay SAM-dependent methyltransferase activity on recombinant nucleosomes,
    measuring methylation state at H3K27 by quantitative mass spectrometry.
  hypothesis: >
    MEZ1 is catalytically active as an H3K27 methyltransferase only (or much more
    efficiently) within an assembled PRC2 complex, consistent with the conserved requirement
    of non-catalytic PRC2 subunits for activity.
  experiment_type: in vitro reconstituted histone methyltransferase assay
- description: >
    Test MEZ1 substrate and residue specificity using SET-domain catalytic point mutants and
    a panel of histone H3 peptides/nucleosomes carrying K27 versus other lysine substrates,
    quantifying product methylation states.
  hypothesis: >
    The conserved E(z) SET domain of MEZ1 confers strict H3K27 specificity, and catalytic-site
    mutations abolish methyltransferase activity without affecting PRC2 assembly.
  experiment_type: structure-function mutagenesis and enzyme specificity assay
references:
- id: PMID:11950982
  title: Sequence relationships, conserved domains, and expression patterns for maize
    homologs of the polycomb group genes E(z), esc, and E(Pc).
  findings:
  - statement: >
      Primary maize reference (Springer et al. 2002) describing the three maize
      Enhancer-of-zeste-like genes Mez1/Mez2/Mez3 (Mez1 = EZ1/MEZ1), their conserved
      PcG domains, and tissue expression; Mez transcripts were detected in all tissues
      tested. PcG proteins act in developmental and epigenetic regulation of gene
      expression, and the cross-kingdom conservation of E(z)/esc homologs indicates a
      conserved role in repressing gene expression.
- id: GO_REF:0000002
  title: >
    Gene Ontology annotation through association of InterPro records with GO terms
  findings:
  - statement: >
      InterPro-to-GO mappings (IPR045318 EZH1/2-like) assign histone methyltransferase
      activity and chromatin remodeling to EZ1.
- id: GO_REF:0000033
  title: Annotation inferences using phylogenetic trees
  findings:
  - statement: >
      E(z)/EZH-family functions (chromatin binding, heterochromatin formation) are conserved
      across the PANTHER PTHR45747 phylogenetic group and propagated to EZ1 by IBA.
- id: GO_REF:0000043
  title: Gene Ontology annotation based on UniProtKB/Swiss-Prot keyword mapping
  findings:
  - statement: >
      SwissProt keyword-derived (SPKW) annotation present in the Sept 2025 goa_uniprot_gcrp
      snapshot but removed from the current GOA release after GOA retired the keyword2GO
      pipeline for cellular organisms.
  - statement: >
      For EZ1, the keyword "Methyltransferase"/"Transferase" mapped to the generic process
      "methylation" (GO:0032259), which drops the substrate; the substrate-specific histone
      H3K27 methyltransferase activity is already annotated, so the generic process term is
      redundant.
- id: GO_REF:0000107
  title: >
    Automatic transfer of experimentally verified manual GO annotation data to orthologs
    using Ensembl Compara
  findings:
  - statement: >
      Annotations transferred from the Arabidopsis (SWN/CLF) and rice E(z) orthologs to
      maize EZ1, including histone H3K27 methyltransferase activity, heterochromatin
      formation, epigenetic negative regulation, and developmental (flowering/photoperiod)
      processes.
- id: GO_REF:0000120
  title: Combined Automated Annotation using Multiple IEA Methods
  findings:
  - statement: >
      Nuclear localization, PcG protein complex membership, and EC-derived histone H3K27
      trimethyltransferase activity assigned to EZ1 by combined IEA methods.
- id: file:MAIZE/EZ1/EZ1-deep-research-falcon.md
  title: >
    Deep-research report (falcon / Edison Scientific Literature) - functional annotation of
    maize EZ1/MEZ1 (Q8S4P6).
  findings:
  - statement: >
      Confirms target identity: maize Mez1 is one of three E(z)-like genes (Mez1/Mez2/Mez3);
      Mez1 is the clf-like homolog while Mez2/Mez3 are EZA1/SWN-like (Springer et al. 2002,
      doi:10.1104/pp.010742), matching UniProt Q8S4P6 as an EZH1/2-like histone-lysine
      methyltransferase.
  - statement: >
      EZ1/MEZ1 is most strongly supported to be a SAM-dependent histone lysine
      methyltransferase acting on H3K27, consistent with its EC assignment in UniProt and its
      E(z)-class SET domain conservation; plant PRC2 deposits H3K27 methylation establishing
      a repressive chromatin state at target loci.
  - statement: >
      PRC2 is a chromatin-associated nuclear complex; most PRC2 proteins localize to the
      nucleus and form multi-subunit complexes, supporting EZ1/MEZ1 nuclear, on-chromatin
      function within PRC2-like assemblies.
  - statement: >
      Maize H3K27me3 marks define facultative heterochromatin attributed to the E(z)/PRC2
      pathway; Mez2/Mez3 mutants reduce H3K27me3 at a subset of loci (partial redundancy);
      Mez1 is uniquely imprinted among the three homologs; direct Mez1 loss-of-function and
      in vitro biochemistry on the maize protein were not available in the retrieved corpus.

Gene Description

Existing Annotations Review

Core Functions

EZ1/MEZ1 is an Enhancer-of-zeste [E(z)]-class SET-domain histone-lysine N-methyltransferase (EC 2.1.1.356) that, as the catalytic subunit of plant Polycomb Repressive Complex 2 (PRC2), uses S-adenosyl-L-methionine to methylate Lys-27 of histone H3 (H3K27me1/2/3).

References

Suggested Questions for Experts

Suggested Experiments

Deep Research

Falcon

Research Report: Maize EZ1 (UniProt Q8S4P6; gene synonyms: EZ1 / MEZ1)

0) Target verification (mandatory disambiguation)

1) Key concepts and definitions (current understanding)

1.1 Polycomb Repressive Complex 2 (PRC2) and H3K27me3

1.2 Where EZ1/MEZ1 fits

2) Functional annotation of maize EZ1/MEZ1

2.1 Primary biochemical function (reaction and substrate)

2.2 Complex context (PRC2 membership in maize endosperm)

3) Biological processes and pathways in maize (direct evidence emphasized)

3.1 Endosperm imprinting and allelic chromatin marking

3.2 Genome-wide H3K27me3 landscape and dependence on maize E(z) homologs

3.3 Endosperm filling: developmental-stage PRC2 activity and quantitative epigenomics

4) Subcellular localization

5) Recent developments and latest research (prioritizing 2023–2024)

5.1 2023: crop PRC2 systems biology (Brassica rapa)

5.2 2023: crop PRC2 components, nuclear localization, and interactions (cotton)

5.3 2024: crop PRC2 catalytic subunit as an agronomic lever (flowering time)

5.4 2024: maize PcG pathway regulators affecting yield-relevant traits

6) Current applications and real-world implementations

6.1 Cereal grain quality/yield levers via PRC2-H3K27me3 control of storage proteins and proliferation

6.2 Flowering-time engineering in Brassica as a PRC2 paradigm

7) Expert analysis and interpretation (bounded by evidence)

8) Key statistics and data points (selected)

9) Evidence summary table

10) Visual evidence from primary maize literature

11) Gaps and recommendations (explicit limitations)

Key primary sources (with dates and URLs)

Artifacts

Citations

📄 View Raw YAML