DNA polymerase I from Yersinia phage phiR8-01 (g022). This is a phage-encoded DNA-directed DNA polymerase (EC 2.7.7.7) that catalyzes the synthesis of DNA during viral genome replication. The protein belongs to DNA polymerase family A and contains a characteristic palm domain for nucleotidyltransferase activity.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
|
GO:0003677
DNA binding
|
IEA
GO_REF:0000002 |
REMOVE |
Summary: While DNA polymerases do bind DNA, this term is too general and does not capture the specific catalytic function. The more specific term DNA-directed DNA polymerase activity (GO:0003887) already implies DNA binding and better represents the molecular function.
Reason: Correctly identified as overly general. DNA binding is inherent in DNA polymerase activity and adds no additional functional information. The specific molecular function GO:0003887 is more informative.
Supporting Evidence:
PMID:35357498
The conserved DNA polymerase PolA motifs A, B and C could be identified from the sequences of several of the most closely related proteins (Supplementary Figures S8 and S9) further confirming the possibility that DNAP01 is a functional DNA polymerase
|
|
GO:0003887
DNA-directed DNA polymerase activity
|
IEA
GO_REF:0000120 |
ACCEPT |
Summary: This is the core molecular function of the protein, directly supported by the EC number 2.7.7.7 and UniProt annotation as "DNA polymerase I, phage-associated". The InterPro domains confirm DNA polymerase family A membership.
Reason: Correctly identified as the core function. EC 2.7.7.7 directly corresponds to DNA-directed DNA polymerase activity. UniProt domain annotation (residues 483-738) and InterPro family classification strongly support this annotation.
Supporting Evidence:
PMID:35357498
DNAP01 was indeed able to replicate the YerA41 DNA thereby creating a non-modified DNA-product... Furthermore, the DNAP01 polymerase did not require any added specific or random hexamer primers for its activity with the YerA41 genomic material
|
|
GO:0006259
DNA metabolic process
|
IEA
GO_REF:0000117 |
REMOVE |
Summary: This term is too broad and non-specific. The more specific terms "DNA-templated DNA replication" (GO:0006261) and "viral DNA genome replication" (GO:0039693) better describe the biological process.
Reason: Appropriately identified as too general. DNA metabolic process encompasses many different processes including repair, recombination, and degradation. The viral-specific replication terms are more informative and accurate for this context.
|
|
GO:0006260
DNA replication
|
IEA
GO_REF:0000120 |
KEEP AS NON CORE |
Summary: Accurate but somewhat general. The more specific term "viral DNA genome replication" (GO:0039693) is more appropriate for a phage polymerase, making this term redundant.
Reason: Upon further consideration, this annotation should be kept as non-core rather than removed. While viral DNA genome replication is more specific, DNA replication is still accurate and represents the broader biological process. This follows GO annotation principles where both general and specific terms can coexist.
Supporting Evidence:
PMID:35357498
DNAP01 was indeed able to replicate the YerA41 DNA thereby creating a non-modified DNA-product
|
|
GO:0006261
DNA-templated DNA replication
|
IEA
GO_REF:0000002 |
KEEP AS NON CORE |
Summary: Appropriate biological process for a DNA polymerase. However, the more specific term "viral DNA genome replication" (GO:0039693) better captures the viral context, making this general term less necessary.
Reason: Correctly identified as non-core. This term accurately describes the mechanism (DNA-templated) but lacks the viral specificity that is the key characteristic of this polymerase. Both general and specific terms are valuable in GO annotation.
Supporting Evidence:
PMID:35357498
When host polymerases are unable to replicate the viral genome, the bacteriophage produces its own polymerase that can function using the modified DNA as a template
|
|
GO:0006302
double-strand break repair
|
IEA
GO_REF:0000118 |
REMOVE |
Summary: TreeGrafter prediction likely based on homology to bacterial DNA polymerase I which has repair functions. However, phage DNA polymerases are primarily dedicated to viral genome replication, not host DNA repair. No evidence supports this specific repair function in the phage context.
Reason: This annotation should be removed rather than marked as over-annotated. There is no evidence that this phage polymerase functions in double-strand break repair. The TreeGrafter prediction appears to be based on superficial homology to bacterial Pol I without considering the specialized viral context. Phage polymerases are optimized for rapid viral genome replication, not DNA repair processes.
Supporting Evidence:
PMID:35357498
Unlike commercially available DNA polymerases, the DNA polymerase coded by the phage's genome should be able to amplify its own modified DNA
|
|
GO:0016740
transferase activity
|
IEA
GO_REF:0000043 |
REMOVE |
Summary: Too general. DNA polymerases are transferases, but the specific term "DNA-directed DNA polymerase activity" (GO:0003887) already encompasses this and is more informative.
Reason: Correctly identified as overly general. Transferase activity is a very broad enzyme classification that includes many different types of enzymes. The specific DNA polymerase molecular function term provides much more biological information.
|
|
GO:0016779
nucleotidyltransferase activity
|
IEA
GO_REF:0000043 |
REMOVE |
Summary: While accurate (DNA polymerases are nucleotidyltransferases), this is less specific than "DNA-directed DNA polymerase activity" (GO:0003887) which better describes the molecular function.
Reason: Correctly identified as less informative than the specific polymerase term. While technically accurate, nucleotidyltransferase activity encompasses many different enzymes including various polymerases, kinases, and other transferases. The DNA polymerase-specific annotation is more valuable.
|
|
GO:0039693
viral DNA genome replication
|
IEA
GO_REF:0000043 |
ACCEPT |
Summary: Highly appropriate and specific biological process for a phage DNA polymerase. This accurately describes the primary role of this protein in viral replication.
Reason: Correctly identified as the most appropriate biological process annotation. This term specifically captures the viral context and primary function of this phage-encoded polymerase. This is the core biological process that the enzyme performs.
Supporting Evidence:
PMID:35357498
The presence of DNAP01 in the phage particles (8) implicates that it is delivered along with the genomic material from the phage particles upon infection into the host bacteria
|
|
GO:0008296
3'-5'-DNA exonuclease activity
|
IEA
GO_REF:0000002 |
NEW |
Summary: This annotation is missing but should be present. Family A DNA polymerases typically possess intrinsic 3'-5' exonuclease activity for proofreading during DNA synthesis.
Reason: This is a key missing annotation. As a family A DNA polymerase, g022 is highly likely to possess 3'-5' exonuclease activity for proofreading function. This is a conserved feature of family A polymerases that improves replication fidelity by removing incorrectly incorporated nucleotides. The deep research confirms this is typical for family A enzymes.
Supporting Evidence:
file:9CAUD/g022/g022-deep-research.md
Family A DNA polymerases, including phage-encoded variants, typically possess intrinsic 3'-5' exonuclease activity that serves as a proofreading mechanism
|
UniProt ID: I7J3R9
Gene Symbol: g022 (locus BN110_032)
Organism: Yersinia phage phiR8-01 (Tequatrovirus genus, Autographiviridae family)
Protein Size: 815 amino acids
EC Number: 2.7.7.7 (DNA-directed DNA polymerase)
Functional Domain: DNA polymerase A domain (residues 483-738)
Bacteriophage DNA polymerases represent a diverse and evolutionarily significant group of enzymes that have adapted to the unique replication requirements of viral genomes. These enzymes often exhibit specialized properties that distinguish them from their cellular counterparts, including enhanced processivity, unique primer requirements, and the ability to replicate modified DNA templates [PMID:35357498, "The DNA polymerase of bacteriophage YerA41 replicates its T-modified DNA in a primer-independent manner reveals Family A conservation with primer-independent activity and high processivity in related Yersinia phages"].
The structural organization of bacteriophage DNA polymerases follows the characteristic "right hand" morphology common to all DNA polymerases, with distinct fingers, palm, and thumb subdomains [PMID:34574025, "Bacteriophage DNA polymerases resemble in overall morphology a cupped human right hand, with fingers (which bind an incoming nucleotide and interact with the single-stranded template), palm (which harbors the catalytic amino acid residues and also binds an incoming dNTP) and thumb (which binds double-stranded DNA) subdomains"].
DNA polymerase family A (Pol A) represents one of the most ancient and widely distributed polymerase families, with members found across all domains of life and their viruses. Prokaryotic family A polymerases include the ubiquitous DNA polymerase I (Pol I) enzyme encoded by the polA gene, which is involved in excision repair and Okazaki fragment processing [PMID:11842093, "Prokaryotic family A polymerases include the DNA polymerase I (Pol I) enzyme, which is encoded by the polA gene and ubiquitous among prokaryotes, involved in excision repair with both 3'–5' and 5'–3' exonuclease activity"].
Evolutionary analyses suggest that the archaeal-type, PolB-based system evolved first among DNA replication machineries, followed by diversification into various viral lineages before the emergence of bacterial PolC-based systems [PMID:17134509, "Among the two types of DNA replication machineries found in extant life forms, the archaeal-type, PolB-based system evolved first and had already given rise to a variety of diverse viruses and other selfish elements before the advent of the bacterial, PolC-based machinery"].
High-resolution crystal structures of DNA polymerases in the Pol I family, including Taq Pol I, E. coli Pol I (Klenow fragment), and bacteriophage T7 DNA polymerase, reveal the characteristic "cupped human right hand" morphology with three distinct subdomains:
Fingers Domain: Binds incoming nucleotides and interacts with single-stranded template DNA. This domain undergoes conformational changes during the nucleotide selection process [PMID:14561325, "The fingers domain binds an incoming nucleotide and interacts with the single-stranded template, undergoing conformational changes during nucleotide selection"].
Palm Domain: Contains the catalytic amino acid residues and represents the most highly conserved domain among different polymerase types. The palm domain harbors essential sequence motifs A and C, with critical aspartate residues located in a hairpin between central β-strands [PMID:12086655, "The palm domain is the most highly conserved domain among different types of polymerases, harboring the catalytic amino acid residues and essential motifs A and C"].
Thumb Domain: Binds double-stranded DNA and contributes to processivity by providing stability to the polymerase-DNA complex [PMID:15084672, "The thumb domain binds double-stranded DNA and contributes to processivity through stabilization of the polymerase-DNA complex"].
The DNA polymerase reaction proceeds through an ordered mechanism involving multiple steps:
This mechanism follows a two-step nucleotide selection process, with initial binding to an entry (E) site followed by rotation into the nucleotide addition (A) site for proper template pairing [PMID:14570949, "The results are consistent with a two-step mechanism of nucleotide selection, with initial binding to an entry (E) site beneath the active center in an inverted orientation, followed by rotation into the nucleotide addition (A) site for pairing with the template DNA"].
Family A DNA polymerases, including phage-encoded variants, typically possess intrinsic 3'-5' exonuclease activity that serves as a proofreading mechanism. This activity is governed by four universally conserved aspartate residues that coordinate two metal ions responsible for hydrolyzing the last phosphodiester bond of the primer strand [PMID:29666393, "The 3′-5′ exonuclease activity is governed by four universally conserved aspartate residues that coordinate the two metal ions responsible for the hydrolysis of the last phosphodiester bond of the primer strand"].
Proofreading Mechanism:
1. Error detection: When an incorrect base pair is recognized, the polymerase moves backward by one base pair
2. Domain transfer: DNA is transferred from the polymerization domain to the 3'-5' exonuclease domain
3. Nucleotide excision: The incorrectly incorporated nucleotide is excised
4. Return to synthesis: DNA moves back to the polymerization domain for continued replication
This proofreading mechanism improves replication fidelity approximately 100-fold, reducing the error rate from ~10^-4 to ~10^-6 per nucleotide incorporated [PMID:12459442, "DNA polymerase proofreading improves replication fidelity ∼ 100-fold, which is required by many organisms to prevent unacceptably high, life threatening mutation loads"].
Many family A polymerases, particularly E. coli DNA polymerase I, possess 5'-3' exonuclease activity in addition to their polymerase and 3'-5' exonuclease functions. This activity is structure-specific, cleaving 5' displaced strands at junctions between single-stranded and duplex regions [PMID:9405471, "The 5′-3′ exonuclease is known to be a structure-specific nuclease that cleaves a 5′ displaced strand at the junction between single-stranded and duplex regions"].
The 5'-3' exonuclease activity is particularly important for:
- Okazaki fragment processing: Removing RNA primers and joining DNA fragments during lagging strand synthesis
- DNA repair: Excising damaged DNA segments during various repair pathways
- Recombination: Processing DNA intermediates during homologous recombination
Bacteriophages have evolved diverse DNA replication strategies that often differ significantly from cellular replication systems. These include:
Protein-primed replication: Exemplified by bacteriophage φ29, where replication initiates through a terminal protein covalently linked to the 5' ends of the linear genome. The terminal protein acts as a primer for the viral DNA polymerase, eliminating the need for RNA primers [PMID:15461462, "In φ29, each 5' end is covalently linked to a terminal protein, which is essential in the replication process by acting as a primer for the viral DNA polymerase"].
Primer-independent initiation: Some phage DNA polymerases can initiate DNA synthesis without external primers, as demonstrated by the NrS-1 polymerase from deep-sea vent phages [PMID:28559297, "The NrS-1 DNA polymerase initiates DNA synthesis from a specific template DNA sequence in the absence of any primer"].
Rolling circle replication: Utilized by various phages for replicating circular DNA molecules through continuous strand displacement synthesis.
In bacteriophage T7, the helicase and polymerase work in close coordination at the replication fork. This coupling allows for active DNA unwinding, with the polymerase providing a separation pin to split the fork while the helicase unwinds the duplex DNA [PMID:34599182, "In bacteriophage T7, helicase and polymerase reside right at the replication fork where the parental DNA is separated into two daughter strands. The two motors pull the two daughter strands to opposite directions, while the polymerase provides a separation pin to split the fork"].
Phage DNA polymerases often exhibit enhanced processivity compared to their cellular counterparts. Processivity refers to the average number of nucleotides added before the enzyme dissociates from the template. While non-processive polymerases add nucleotides at approximately one per second, processive polymerases can add multiple nucleotides per second [PMID:25106265, "While nonprocessive DNA polymerases add nucleotides at a rate of one nucleotide per second, processive DNA polymerases add multiple nucleotides per second, drastically increasing the rate of DNA synthesis"].
Mechanisms enhancing processivity:
- Sliding clamps: Ring-shaped proteins that encircle DNA and tether the polymerase
- Specialized domains: Additional domains that increase DNA binding affinity
- Protein-protein interactions: Coupling with other replication machinery components
DNA polymerase fidelity is achieved through multiple mechanisms:
Geometric selection: The polymerase active site is optimized to accommodate only correctly paired nucleotides, discriminating against mispairs based on geometric constraints [PMID:14698632, "Replicative DNA polymerases must synthesize DNA with high fidelity, with most having evolved to promote proper base pairing"].
Induced fit: Conformational changes upon correct nucleotide binding increase the catalytic efficiency for properly paired substrates while reducing efficiency for mispaired substrates.
Proofreading: The 3'-5' exonuclease activity provides a second checkpoint, removing incorrectly incorporated nucleotides [PMID:12459442, "The 3'→5' exonuclease activity of A- and B-family polymerases additionally assures the correctness of the nascent DNA strand"].
Phage DNA polymerases function within complex replisome assemblies that coordinate various aspects of DNA replication. The NrS-1 DNA polymerase forms a replisome with phage-encoded helicase and single-strand DNA-binding protein to enhance processivity, similar to the bacteriophage T7 replisome [PMID:28559297, "The NrS-1 DNA polymerase forms a replisome with phage-encoded helicase and ssDNA-binding protein to enhance processivity, similar to the bacteriophage T7 replisome"].
Various accessory proteins modulate polymerase activity:
Single-strand DNA-binding proteins (SSB): Stabilize single-stranded DNA regions and facilitate polymerase progression
Helicases: Unwind duplex DNA ahead of the replication fork
Primase: Synthesizes RNA primers for leading and lagging strand synthesis (though some phage polymerases can initiate synthesis de novo)
Sliding clamps: Enhance processivity by tethering the polymerase to DNA
Many bacteriophages incorporate modified nucleotides into their genomes as a defense mechanism against host restriction endonucleases. Phage DNA polymerases have evolved specialized capabilities to replicate these hypermodified templates efficiently [PMID:35357498, "Bacteriophage DNA polymerases are specialized to handle hypermodified viral DNA templates that contain modified bases unique to the phage"].
Examples of DNA modifications:
- Hydroxymethylcytosine: Found in T4 phage DNA
- 5-methylcytosine: Present in various phage genomes
- Glucosylated bases: Additional modifications that further protect against restriction
Phage DNA polymerases are often packaged within virion particles to ensure immediate availability upon infection. This packaging strategy allows for rapid initiation of viral DNA replication without relying on host cell machinery [PMID:35357498, "Viral DNA polymerases are delivered within phage particles during infection, ensuring immediate availability for viral genome replication"].
Despite functional specialization, viral and cellular DNA polymerases share fundamental structural features:
Conserved active site architecture: The catalytic palm domain shows remarkable conservation across all polymerase families
Metal ion coordination: Universal requirement for divalent metal ions (typically Mg²⁺ or Mn²⁺) in the active site
Substrate binding sites: Similar nucleotide and DNA binding mechanisms
Primer requirements: While most cellular polymerases require primers, some viral polymerases can initiate synthesis de novo
Processivity: Viral polymerases often exhibit higher processivity to enable rapid genome replication
Template specificity: Viral polymerases may be adapted to replicate modified DNA templates
Size and complexity: Viral polymerases are often smaller and less complex than cellular replicative polymerases
Phylogenetic analyses reveal complex evolutionary relationships between viral and cellular polymerases, with evidence for multiple horizontal gene transfer events [PMID:17134509, "Mixing of viral and cellular sequences in phylogenetic analyses suggests that many transfers of these enzymes have taken place between cells and viruses (in either direction)"].
Key evolutionary insights:
- Viral polymerases show closer relationships to each other than to their host polymerases in some cases
- Evidence for ancient viral origins of some polymerase lineages
- Horizontal gene transfer has shaped polymerase evolution
Phage DNA polymerases have undergone adaptive evolution to optimize:
Replication speed: Rapid completion of the viral life cycle
Host range: Adaptation to different bacterial hosts
Immune evasion: Resistance to host defense mechanisms
DNA modification: Ability to incorporate or replicate modified nucleotides
Phage DNA polymerases have found extensive use in molecular biology applications:
High-fidelity PCR: Polymerases with 3'-5' exonuclease activity provide enhanced accuracy for PCR amplification [PMID:8289329, "PCR performed with DNA polymerase containing 3'-5' exonuclease activity yields amplification products containing significantly fewer mutations compared to Taq polymerase"].
Multiple Displacement Amplification (MDA): φ29 polymerase is widely used in MDA procedures for whole genome amplification, capable of producing fragments tens of kilobases in length [PMID:15084672, "φ29 polymerase enzyme is used in multiple displacement amplification (MDA) procedures whereby fragments tens of kilobases in length can be produced from non-specific hexameric primers"].
Real-time PCR: The 5'-3' exonuclease activity of certain thermostable polymerases enables real-time PCR detection through probe cleavage [PMID:1363668, "The 5'→3' exonuclease activity of thermostable enzyme may be employed in PCR product detection systems to generate specific detectable signals concomitantly with amplification"].
DNA synthesis: High-fidelity polymerases enable accurate synthesis of long DNA constructs
Genome editing: Polymerases with specialized properties support various genome editing approaches
Diagnostic applications: Thermostable polymerases from phages enable robust diagnostic PCR assays
Based on sequence analysis and comparison with characterized family A polymerases, g022 likely contains:
N-terminal region: May contain regulatory or DNA-binding domains
Central polymerase domain (residues 483-738): Contains the catalytic palm, fingers, and thumb subdomains
C-terminal region: May contain additional functional domains or protein interaction sites
As a family A DNA polymerase, g022 is expected to contain:
Motif A: Contains the conserved aspartate residue crucial for metal ion coordination
Motif B: Involved in nucleotide binding and positioning
Motif C: Contains the second conserved aspartate residue for catalysis
These motifs are essential for polymerase activity and are highly conserved across all family A members [PMID:35357498, "Family A DNA polymerases contain conserved PolA motifs A, B, and C that are essential for catalytic activity"].
As a DNA-directed DNA polymerase (EC 2.7.7.7), g022 catalyzes the formation of phosphodiester bonds between nucleotides in a template-directed manner. The reaction mechanism involves:
Based on its family A classification and viral origin, g022 likely exhibits:
Moderate to high processivity: Enabling efficient replication of the phage genome
Template-dependent synthesis: Requiring a DNA template for activity
Primer-dependent initiation: Most likely requiring a primer for synthesis initiation, though some viral polymerases can initiate de novo
3'-5' exonuclease: Likely present based on family A classification, providing proofreading capability
5'-3' exonuclease: Potentially present, though not universal among all family A polymerases
As a member of the Tequatrovirus genus, phage phiR8-01 likely follows a lytic life cycle characterized by:
DNA polymerase expression is typically regulated during the viral life cycle:
Early gene expression: g022 may be expressed early in infection to initiate genome replication
DNA packaging: Newly synthesized genomes are packaged into virion heads
Virion maturation: Assembly of complete infectious particles
Phage DNA polymerases must function in the presence of host defense mechanisms:
Restriction-modification systems: Host endonucleases that cleave foreign DNA
CRISPR-Cas systems: Adaptive immune systems that target viral nucleic acids
Interferon responses: Antiviral signaling pathways (in eukaryotic hosts)
Nucleotide pools: Competition with host DNA synthesis for dNTP substrates
Replication machinery: Potential interaction with or displacement of host replication proteins
Cellular energy: Utilization of host ATP and other energy sources
Yersinia species are important human and animal pathogens:
Y. pestis: Causative agent of plague
Y. enterocolitica: Causes gastroenteritis
Y. pseudotuberculosis: Causes mesenteric lymphadenitis
Understanding phage biology in these species has implications for:
- Phage therapy: Potential use of phages as antimicrobial agents
- Bacterial typing: Phage sensitivity patterns for strain identification
- Virulence modulation: Effects of phage infection on bacterial pathogenicity
Biocontrol: Phages targeting plant pathogenic Yersinia species
Food safety: Detection and control of foodborne Yersinia pathogens
Environmental monitoring: Tracking Yersinia populations in agricultural systems
X-ray crystallography: High-resolution structure determination of g022
Cryo-electron microscopy: Visualization of replication complexes
NMR spectroscopy: Solution structure and dynamics studies
Biochemical assays: Kinetic parameters, processivity measurements, and substrate specificity
Single-molecule studies: Real-time observation of polymerase activity
Mutational analysis: Structure-function relationships
Enzyme engineering: Optimization for specific applications
Thermostability enhancement: Development of heat-stable variants
Novel applications: Exploration of unique properties for biotechnology
The g022 gene from Yersinia phage phiR8-01 encodes a DNA polymerase I that represents a fascinating example of viral adaptation and evolution. As a member of the ancient family A polymerase lineage, g022 likely retains core catalytic mechanisms while possessing specialized features that enable efficient replication of the Tequatrovirus genome.
Key features of g022 include:
Evolutionary significance: Part of an ancient polymerase family with complex evolutionary relationships between viral and cellular lineages
Catalytic efficiency: DNA-directed DNA polymerase activity (EC 2.7.7.7) with likely proofreading capability through 3'-5' exonuclease activity
Viral specialization: Adaptations for rapid genome replication in the viral life cycle context
Biotechnological potential: Possible applications in molecular biology techniques requiring high-fidelity DNA synthesis
Host interaction: Function within the complex ecological relationship between Tequatrovirus phages and their Yersinia hosts
The study of g022 and related viral polymerases continues to provide insights into fundamental mechanisms of DNA replication, the evolution of replication machinery, and the development of new biotechnological tools. As our understanding of phage biology expands, proteins like g022 may find increasing applications in research, diagnostics, and therapeutic development.
Further research on g022 would benefit from detailed biochemical characterization, structural studies, and investigation of its role in the complete Tequatrovirus replication machinery. Such studies would not only advance our understanding of viral DNA replication but also potentially reveal new opportunities for biotechnological applications and therapeutic interventions.
This comprehensive review synthesizes current knowledge about DNA polymerase structure, function, and evolution, with specific focus on viral adaptations and biotechnological applications. The information presented draws from extensive literature on DNA polymerases, viral replication mechanisms, and comparative genomics studies that illuminate the fascinating biology of phage-encoded replication enzymes like g022.
g022 represents a DNA polymerase from the Tequatrovirus genus:
- Host range: Tequatroviruses infect Enterobacteriaceae including Yersinia
- Viral replication: Essential for autonomous viral DNA synthesis
- Family A properties: Shares conserved motifs with other DNA polymerases
- Viral packaging: Likely packaged in virion for immediate use post-infection
- Template adaptation: May handle modified DNA bases unique to the phage
id: I7J3R9
gene_symbol: I7J3R9
taxon:
id: NCBITaxon:10663
label: Tequatrovirus
description: DNA polymerase I from Yersinia phage phiR8-01 (g022). This is a phage-encoded
DNA-directed DNA polymerase (EC 2.7.7.7) that catalyzes the synthesis of DNA during
viral genome replication. The protein belongs to DNA polymerase family A and contains
a characteristic palm domain for nucleotidyltransferase activity.
existing_annotations:
- term:
id: GO:0003677
label: DNA binding
evidence_type: IEA
original_reference_id: GO_REF:0000002
review:
summary: While DNA polymerases do bind DNA, this term is too general and does
not capture the specific catalytic function. The more specific term DNA-directed
DNA polymerase activity (GO:0003887) already implies DNA binding and better
represents the molecular function.
action: REMOVE
reason: Correctly identified as overly general. DNA binding is inherent in DNA
polymerase activity and adds no additional functional information. The specific
molecular function GO:0003887 is more informative.
supported_by:
- reference_id: PMID:35357498
supporting_text: The conserved DNA polymerase PolA motifs A, B and C could be
identified from the sequences of several of the most closely related proteins
(Supplementary Figures S8 and S9) further confirming the possibility that DNAP01
is a functional DNA polymerase
- term:
id: GO:0003887
label: DNA-directed DNA polymerase activity
evidence_type: IEA
original_reference_id: GO_REF:0000120
review:
summary: This is the core molecular function of the protein, directly supported
by the EC number 2.7.7.7 and UniProt annotation as "DNA polymerase I, phage-associated".
The InterPro domains confirm DNA polymerase family A membership.
action: ACCEPT
reason: Correctly identified as the core function. EC 2.7.7.7 directly corresponds
to DNA-directed DNA polymerase activity. UniProt domain annotation (residues
483-738) and InterPro family classification strongly support this annotation.
supported_by:
- reference_id: PMID:35357498
supporting_text: DNAP01 was indeed able to replicate the YerA41 DNA thereby
creating a non-modified DNA-product... Furthermore, the DNAP01 polymerase
did not require any added specific or random hexamer primers for its activity
with the YerA41 genomic material
- term:
id: GO:0006259
label: DNA metabolic process
evidence_type: IEA
original_reference_id: GO_REF:0000117
review:
summary: This term is too broad and non-specific. The more specific terms "DNA-templated
DNA replication" (GO:0006261) and "viral DNA genome replication" (GO:0039693)
better describe the biological process.
action: REMOVE
reason: Appropriately identified as too general. DNA metabolic process encompasses
many different processes including repair, recombination, and degradation. The
viral-specific replication terms are more informative and accurate for this
context.
- term:
id: GO:0006260
label: DNA replication
evidence_type: IEA
original_reference_id: GO_REF:0000120
review:
summary: Accurate but somewhat general. The more specific term "viral DNA genome
replication" (GO:0039693) is more appropriate for a phage polymerase, making
this term redundant.
action: KEEP_AS_NON_CORE
reason: Upon further consideration, this annotation should be kept as non-core
rather than removed. While viral DNA genome replication is more specific, DNA
replication is still accurate and represents the broader biological process.
This follows GO annotation principles where both general and specific terms
can coexist.
supported_by:
- reference_id: PMID:35357498
supporting_text: DNAP01 was indeed able to replicate the YerA41 DNA thereby
creating a non-modified DNA-product
- term:
id: GO:0006261
label: DNA-templated DNA replication
evidence_type: IEA
original_reference_id: GO_REF:0000002
review:
summary: Appropriate biological process for a DNA polymerase. However, the more
specific term "viral DNA genome replication" (GO:0039693) better captures the
viral context, making this general term less necessary.
action: KEEP_AS_NON_CORE
reason: Correctly identified as non-core. This term accurately describes the mechanism
(DNA-templated) but lacks the viral specificity that is the key characteristic
of this polymerase. Both general and specific terms are valuable in GO annotation.
supported_by:
- reference_id: PMID:35357498
supporting_text: When host polymerases are unable to replicate the viral genome,
the bacteriophage produces its own polymerase that can function using the
modified DNA as a template
- term:
id: GO:0006302
label: double-strand break repair
evidence_type: IEA
original_reference_id: GO_REF:0000118
review:
summary: TreeGrafter prediction likely based on homology to bacterial DNA polymerase
I which has repair functions. However, phage DNA polymerases are primarily dedicated
to viral genome replication, not host DNA repair. No evidence supports this
specific repair function in the phage context.
action: REMOVE
reason: This annotation should be removed rather than marked as over-annotated.
There is no evidence that this phage polymerase functions in double-strand break
repair. The TreeGrafter prediction appears to be based on superficial homology
to bacterial Pol I without considering the specialized viral context. Phage
polymerases are optimized for rapid viral genome replication, not DNA repair
processes.
supported_by:
- reference_id: PMID:35357498
supporting_text: Unlike commercially available DNA polymerases, the DNA polymerase
coded by the phage's genome should be able to amplify its own modified DNA
- term:
id: GO:0016740
label: transferase activity
evidence_type: IEA
original_reference_id: GO_REF:0000043
review:
summary: Too general. DNA polymerases are transferases, but the specific term
"DNA-directed DNA polymerase activity" (GO:0003887) already encompasses this
and is more informative.
action: REMOVE
reason: Correctly identified as overly general. Transferase activity is a very
broad enzyme classification that includes many different types of enzymes. The
specific DNA polymerase molecular function term provides much more biological
information.
- term:
id: GO:0016779
label: nucleotidyltransferase activity
evidence_type: IEA
original_reference_id: GO_REF:0000043
review:
summary: While accurate (DNA polymerases are nucleotidyltransferases), this is
less specific than "DNA-directed DNA polymerase activity" (GO:0003887) which
better describes the molecular function.
action: REMOVE
reason: Correctly identified as less informative than the specific polymerase
term. While technically accurate, nucleotidyltransferase activity encompasses
many different enzymes including various polymerases, kinases, and other transferases.
The DNA polymerase-specific annotation is more valuable.
- term:
id: GO:0039693
label: viral DNA genome replication
evidence_type: IEA
original_reference_id: GO_REF:0000043
review:
summary: Highly appropriate and specific biological process for a phage DNA polymerase.
This accurately describes the primary role of this protein in viral replication.
action: ACCEPT
reason: Correctly identified as the most appropriate biological process annotation.
This term specifically captures the viral context and primary function of this
phage-encoded polymerase. This is the core biological process that the enzyme
performs.
supported_by:
- reference_id: PMID:35357498
supporting_text: The presence of DNAP01 in the phage particles (8) implicates
that it is delivered along with the genomic material from the phage particles
upon infection into the host bacteria
- term:
id: GO:0008296
label: 3'-5'-DNA exonuclease activity
evidence_type: IEA
original_reference_id: GO_REF:0000002
review:
summary: This annotation is missing but should be present. Family A DNA polymerases
typically possess intrinsic 3'-5' exonuclease activity for proofreading during
DNA synthesis.
action: NEW
reason: This is a key missing annotation. As a family A DNA polymerase, g022 is
highly likely to possess 3'-5' exonuclease activity for proofreading function.
This is a conserved feature of family A polymerases that improves replication
fidelity by removing incorrectly incorporated nucleotides. The deep research
confirms this is typical for family A enzymes.
supported_by:
- reference_id: file:9CAUD/g022/g022-deep-research.md
supporting_text: Family A DNA polymerases, including phage-encoded variants,
typically possess intrinsic 3'-5' exonuclease activity that serves as a proofreading
mechanism
core_functions:
- description: Catalyzes the synthesis of DNA from deoxynucleoside triphosphates using
DNA as a template during viral genome replication
molecular_function:
id: GO:0003887
label: DNA-directed DNA polymerase activity
directly_involved_in:
- id: GO:0039693
label: viral DNA genome replication
- description: Provides 3'-5' exonuclease activity for proofreading during DNA synthesis,
improving replication fidelity by removing incorrectly incorporated nucleotides
molecular_function:
id: GO:0008296
label: 3'-5'-DNA exonuclease activity
supported_by:
- reference_id: file:9CAUD/g022/g022-deep-research.md
supporting_text: Family A DNA polymerases, including phage-encoded variants, typically
possess intrinsic 3'-5' exonuclease activity that serves as a proofreading mechanism
directly_involved_in:
- id: GO:0039693
label: viral DNA genome replication
references:
- id: PMID:35357498
title: The DNA polymerase of bacteriophage YerA41 replicates its T-modified DNA
in a primer-independent manner.
findings:
- statement: Bacteriophage DNA polymerases can function with extensively modified
DNA templates that are resistant to conventional DNA polymerases
supporting_text: Unlike commercially available DNA polymerases, the DNA polymerase
coded by the phage's genome should be able to amplify its own modified DNA.
When host polymerases are unable to replicate the viral genome, the bacteriophage
produces its own polymerase that can function using the modified DNA as a template
full_text_unavailable: false
- statement: YerA41 phage DNA polymerase demonstrates primer-independent replication
activity with modified viral genomic DNA
supporting_text: We expressed and purified DNAP01, which showed DNA polymerase
activity and was able to use the YerA41 genomic material as a template without
any added primers, with just added dNTPs
full_text_unavailable: false
- statement: YerA41 DNA polymerase contains conserved PolA motifs A, B and C characteristic
of family A DNA polymerases
supporting_text: The conserved DNA polymerase PolA motifs A, B and C could be
identified from the sequences of several of the most closely related proteins
(Supplementary Figures S8 and S9) further confirming the possibility that DNAP01
is a functional DNA polymerase of YerA41
full_text_unavailable: false
- statement: Phage DNA polymerase is packaged within viral particles and delivered
during infection
supporting_text: The presence of DNAP01 in the phage particles (8) implicates
that it is delivered along with the genomic material from the phage particles
upon infection into the host bacteria. DNAP01 should inherently possess the
ability to use the YerA41 DNA as template
full_text_unavailable: false
- statement: Bacteriophage DNA polymerase functions without external primers and
shows high processivity
supporting_text: DNAP01 was indeed able to replicate the YerA41 DNA thereby creating
a non-modified DNA-product... Furthermore, the DNAP01 polymerase did not require
any added specific or random hexamer primers for its activity with the YerA41
genomic material... DNAP01 demonstrated apparent high progressivity in experiments
where it was incubated different times with the YerA41 genomic material as a
mere one-minute incubation was sufficient
full_text_unavailable: false
- statement: The C-terminal domain of phage DNA polymerase contains the active polymerase
function
supporting_text: As the structural modelling of DNAP01 predicted that the DNA
polymerase activity would reside in its C-terminal domain (DNAP01-Ct, residues
946–1306 of the full-length, Supplementary Figure S8), it was also selected
for expression cloning
full_text_unavailable: false
- id: GO_REF:0000002
title: Gene Ontology annotation through association of InterPro records with GO
terms.
full_text_unavailable: false
findings: []
- id: GO_REF:0000043
title: Gene Ontology annotation based on UniProtKB/Swiss-Prot keyword mapping
full_text_unavailable: false
findings: []
- id: GO_REF:0000117
title: Electronic Gene Ontology annotations created by ARBA machine learning models
full_text_unavailable: false
findings: []
- id: GO_REF:0000118
title: TreeGrafter-generated GO annotations
full_text_unavailable: false
findings: []
- id: GO_REF:0000120
title: Combined Automated Annotation using Multiple IEA Methods.
full_text_unavailable: false
findings: []
status: COMPLETE