GO:0000731 DNA synthesis involved in DNA repair: Mechanism, Genes, Functions and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0000731 (DNA synthesis involved in DNA repair) describes DNA synthesis that starts from a broken 3' single-strand DNA end and uses the homologous intact duplex as the template.
• This process is central to homologous recombination-dependent repair and to gap-filling steps of nucleotide excision repair and interstrand crosslink repair.
• Replication fork reversal creates a 3' single-strand end that can prime DNA synthesis involved in DNA repair, linking fork remodeling to repair synthesis.
• Translesion synthesis polymerases can extend from a 3' end during repair, but they are error-prone and must be tightly regulated.
• Defects in repair synthesis are associated with cancer predisposition, chemoresistance, and sensitivity to DNA-damaging agents such as hydroxyurea.
• CRISPR knockout, point-mutation, knock-in, and overexpression models allow causal testing of genes that execute DNA synthesis involved in DNA repair.
Description
GO:0000731, DNA synthesis involved in DNA repair, is a biological process defined as synthesis of DNA that proceeds from the broken 3' single-strand DNA end and uses the homologous intact duplex as the template. This definition places the term at the intersection of DNA strand exchange, primer extension, and template-directed polymerization during repair of damaged or broken chromosomes. The process is not a single enzyme reaction but a coordinated series of events in which a 3' single-strand end is generated, stabilized, and then extended by a DNA polymerase using an intact homologous duplex as the template. Researchers study GO:0000731 because it determines whether a cell survives DNA damage with high fidelity or resorts to error-prone bypass, and because its dysregulation is linked to genome instability and disease. The term is especially relevant to homologous recombination, replication fork reversal, nucleotide excision repair gap filling, and interstrand crosslink repair, where repair synthesis is required to restore an intact duplex. Because the 3' end is the defining substrate, the process is mechanistically distinct from de novo DNA synthesis at replication origins and from simple nick translation.
DNA synthesis involved in DNA repair At A Glance
| GO ID | GO:0000731 |
|---|---|
| GO term | DNA synthesis involved in DNA repair |
| Ontology | biological_process |
| Synonym | DNA repair synthesis; DNA synthesis during DNA repair; mitotic DNA repair synthesis |
| Definition | Synthesis of DNA that proceeds from the broken 3' single-strand DNA end and uses the homologous intact duplex as the template |
| Major function | Template-directed extension of a 3' single-strand end during repair of DNA damage or breaks |
| Related processes | Homologous recombination, replication fork reversal, nucleotide excision repair, interstrand crosslink repair, translesion synthesis |
| Key polymerases | Repair and translesion synthesis DNA polymerases that extend from a 3' end |
| Disease relevance | Cancer predisposition, chemoresistance, and sensitivity to DNA-damaging agents |
What Is GO:0000731?
In simple terms, DNA synthesis involved in DNA repair is the copying step that fills in missing DNA using a broken 3' end as the starting point and an intact matching DNA strand as the instruction template. The QuickGO definition states that it is the synthesis of DNA that proceeds from the broken 3' single-strand DNA end and uses the homologous intact duplex as the template. This distinguishes it from other DNA synthesis reactions because the primer is a damaged or resected chromosomal end rather than a canonical replication origin or RNA primer. The process is therefore template-directed and homology-dependent, and it is often coupled to strand invasion, gap filling, and restoration of the original DNA sequence.
Why Is DNA synthesis involved in DNA repair Important in Cell Biology?
DNA synthesis involved in DNA repair is important because it is the step that actually restores missing genetic information after a break or lesion, and its fidelity determines whether repair is error-free or mutagenic. When this process fails or is misregulated, cells accumulate mutations, become dependent on alternative repair pathways, or die, which directly affects cancer development and the response to chemotherapy and radiotherapy. Because the 3' single-strand end is the defining substrate, the process is also a focal point for understanding how replication fork reversal, strand invasion, and polymerase switching are coordinated.
• It restores missing DNA sequence after breaks, gaps, and crosslinks using an intact homologous duplex as the template.
• It is required for error-free repair of replication-associated DNA damage and for recovery from fork stalling.
• It is a key step in nucleotide excision repair gap filling in human cells.
• It contributes to interstrand crosslink repair, where repair synthesis must occur after unhooking and incision.
• Translesion synthesis polymerases can perform repair synthesis but may introduce mutations, linking the process to mutagenesis.
• Its dysfunction is associated with cancer predisposition and with sensitivity to hydroxyurea and other DNA-damaging agents.
• It is a determinant of chemoresistance because cancer cells can upregulate repair synthesis to survive genotoxic therapy.
• It is mechanistically coupled to replication fork reversal and genome maintenance pathways.
• It provides a therapeutic target when tumors depend on a specific repair synthesis polymerase.
• It can be studied with CRISPR models to test causality of candidate repair genes.
What Happens During DNA synthesis involved in DNA repair?
Generation of the broken 3' single-strand end
In simple terms: First, the cell creates or exposes a free 3' DNA end that can act as the starting point for copying.
The process begins when a DNA break or lesion is processed to expose a 3' single-strand DNA end. Replication fork reversal is one mechanism that generates a reversed fork with a 3' end that can prime repair synthesis. Resection and end processing at double-strand breaks also produce 3' single-strand tails that are substrates for homology-dependent repair synthesis. The availability and structure of this 3' end determine whether repair synthesis can proceed and which polymerase is recruited.
Homologous template engagement and strand invasion
In simple terms: The broken end finds and pairs with an intact matching DNA sequence that will serve as the template.
Once a 3' single-strand end is available, it must engage an intact homologous duplex to serve as the template. This homology search and strand invasion step is a hallmark of homologous recombination and is required for template-directed repair synthesis. The intact duplex provides the correct sequence information so that repair synthesis can restore the original DNA sequence rather than introducing errors. In replication-associated repair, the sister chromatid is the preferred template, which helps ensure high-fidelity repair.
Polymerase recruitment and primer extension
In simple terms: A DNA polymerase binds the 3' end and starts adding new DNA letters using the intact strand as a guide.
After strand invasion, a DNA polymerase extends the 3' end using the homologous duplex as the template. This is the catalytic core of GO:0000731 and can be performed by replicative or repair-specific polymerases depending on the context. In nucleotide excision repair, repair synthesis fills the gap left after excision of a damaged base, and specific polymerases are required for this step in human cells. In interstrand crosslink repair, translesion synthesis polymerases can extend from the 3' end after unhooking, although this can be error-prone.
Gap filling and ligation
In simple terms: The copied patch is sealed to the rest of the DNA so the strand is continuous again.
Repair synthesis does not end with polymerase extension; the newly synthesized patch must be joined to the adjacent DNA. Gap filling and ligation restore strand continuity and complete the repair event. In translesion synthesis gap-filling models, the polymerase extends from the 3' end and the remaining nick is sealed by ligation. Failure to complete this step leaves persistent nicks or gaps that can trigger further genome instability.
Polymerase switching and damage tolerance
In simple terms: If the template is damaged, the cell may switch to a more flexible but less accurate polymerase to finish the job.
When the template contains a lesion that blocks a high-fidelity polymerase, cells can switch to translesion synthesis polymerases to extend from the 3' end. This polymerase switching is a regulated decision that balances completion of repair synthesis against the risk of mutation. O6-alkylguanine lesions, for example, can be bypassed by translesion synthesis in human cells, linking repair synthesis to alkylation damage tolerance. The involvement of translesion synthesis polymerases in interstrand crosslink repair further shows that repair synthesis can be completed by specialized enzymes when needed.
Key Genes Involved in GO:0000731 DNA synthesis involved in DNA repair
The genes and proteins below are experimentally implicated in DNA synthesis involved in DNA repair, including polymerases, fork-remodeling factors, and repair pathway components.
| Gene | Major Role | Research Relevance |
|---|---|---|
| POLH | Translesion synthesis polymerase that can extend from a 3' end | Tests error-prone repair synthesis and UV damage tolerance |
| POLI | Translesion synthesis polymerase involved in bypass of damaged bases | Models polymerase switching during repair synthesis |
| POLK | Translesion synthesis polymerase implicated in gap filling | Studies mutagenic repair synthesis and lesion bypass |
| REV1 | Scaffold and polymerase for translesion synthesis | Central to polymerase switching during repair synthesis |
| REV3L | Catalytic subunit of polymerase zeta | Tests extension from 3' ends during damage tolerance |
| PCNA | Sliding clamp that coordinates polymerase recruitment | Target for studying repair synthesis regulation |
| RAD51 | Strand invasion and homologous template engagement | Required for homology-dependent repair synthesis |
| BRCA1 | Homologous recombination and fork protection | Links repair synthesis to genome maintenance |
| BRCA2 | RAD51 loading and homologous recombination | Models defective repair synthesis and cancer risk |
| FANCD2 | Interstrand crosslink repair and unhooking | Tests repair synthesis after crosslink unhooking |
| FANCI | Interstrand crosslink repair complex | Studies coordination of incision and repair synthesis |
| ERCC1 | Nucleotide excision repair incision and gap filling | Models NER repair synthesis defects |
| XPF | Nuclease for NER and crosslink repair | Tests repair synthesis after incision |
| XPA | Damage recognition in nucleotide excision repair | Upstream of repair synthesis gap filling |
| SMARCAL1 | Fork reversal and remodeling | Links fork reversal to 3' end generation |
| ZRANB3 | Fork reversal and remodeling | Studies repair synthesis priming after reversal |
| HLTF | Fork reversal and genome maintenance | Models replication-associated repair synthesis |
How Is DNA synthesis involved in DNA repair Regulated?
DNA synthesis involved in DNA repair is regulated at multiple levels, including polymerase recruitment, post-translational modification of sliding clamps, and cell cycle control. Replication fork reversal and remodeling factors determine when a 3' end becomes available to prime repair synthesis. Translesion synthesis polymerases are tightly controlled because their use can introduce mutations, and their switching is coordinated with PCNA modification and repair pathway choice. In nucleotide excision repair, the choice of polymerase for gap filling is influenced by the lesion and chromatin context. Interstrand crosslink repair requires coordination between incision, unhooking, and repair synthesis, and defects in this regulation cause sensitivity to crosslinking agents. Hydroxyurea treatment perturbs replication and can indirectly affect repair synthesis by altering dNTP pools and fork progression. Genome maintenance pathways that sense mechanical and replication stress also influence repair synthesis decisions.
DNA synthesis involved in DNA repair and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| BRCA1 | Hereditary breast and ovarian cancer; homologous recombination deficiency | Knockout and point-mutation cell models |
| BRCA2 | Hereditary breast and ovarian cancer; Fanconi anemia subtype | Knock-in and knockout models |
| FANCD2 | Fanconi anemia; interstrand crosslink repair defect | Knockout and tagged knock-in models |
| POLH | Xeroderma pigmentosum variant; translesion synthesis defect | Point-mutation and knockout models |
| REV1 | Cancer chemoresistance; translesion synthesis | Overexpression and knockout models |
Cancer predisposition and genome instability
Defects in homology-dependent repair synthesis and in the genes that support it cause genome instability and are associated with cancer predisposition. Loss of BRCA1 or BRCA2 function impairs homologous recombination and repair synthesis, leading to reliance on error-prone pathways. Translesion synthesis polymerases can promote mutagenesis during repair synthesis, contributing to the mutation burden in tumors.
Chemoresistance and sensitivity to DNA-damaging agents
Cancer cells can upregulate repair synthesis to survive chemotherapy and radiotherapy, making this process a determinant of treatment response. Conversely, cells defective in repair synthesis are sensitive to agents such as hydroxyurea and crosslinking drugs. Targeting translesion synthesis polymerases is being explored to overcome resistance to DNA-damaging therapy.
Interstrand crosslink repair disorders
Interstrand crosslink repair requires incision, unhooking, and repair synthesis, and defects in this pathway cause hypersensitivity to crosslinking agents. Fanconi anemia proteins such as FANCD2 and FANCI coordinate these steps, and their loss impairs repair synthesis after crosslink unhooking. Experimental models in yeast and human cells have been used to dissect the repair synthesis steps induced by crosslinking and metal-based compounds.
From DNA synthesis involved in DNA repair-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| Is a candidate gene required for repair synthesis? | CRISPR knockout cell line |
| Does a specific residue control polymerase recruitment? | Point-mutation knock-in |
| Can a tagged protein track repair synthesis foci? | Tagged knock-in |
| Does overexpression drive chemoresistance? | Overexpression cell model |
| Which genes are synthetic lethal with repair synthesis defects? | CRISPR library screening |
| How does fork reversal affect 3' end availability? | Knockout and live-cell imaging models |
How to Study the DNA synthesis involved in DNA repair Process
| Method | What It Measures | Typical Application |
|---|---|---|
| Labeled nucleotide incorporation | Repair synthesis activity | NER and translesion synthesis gap filling |
| Repair foci imaging | Recruitment of repair synthesis factors | Homologous recombination and fork reversal |
| Live-cell fork imaging | Fork reversal and 3' end generation | Replication-associated repair synthesis |
| Genome-wide sequencing | Mutation signatures from repair synthesis | Translesion synthesis mutagenesis |
| Proteomics | Polymerase complex composition | Polymerase switching studies |
| Yeast genetic assays | Pathway requirement for repair synthesis | Lesion-specific repair pathway mapping |
| CRISPR knockout | Causal requirement for a gene | Repair synthesis gene discovery |
| CRISPR library screening | Synthetic lethal interactions | Target discovery in repair-deficient cells |
Measuring repair synthesis with labeled nucleotides
Repair synthesis can be measured by incorporating labeled or modified nucleotides into DNA after damage, followed by detection of incorporated signal at repair sites. This approach is used in nucleotide excision repair and translesion synthesis studies to quantify gap filling. Combining labeling with damage agents such as UV or crosslinkers allows pathway-specific measurement.
Imaging repair foci and fork dynamics
Live-cell imaging of repair factors and fork remodeling proteins reveals when and where 3' ends are generated and extended. Foci of RAD51, BRCA1, and PCNA can be used as proxies for repair synthesis activity. Fork reversal events can be visualized with tagged remodeling factors such as SMARCAL1 and ZRANB3.
Genomic and proteomic profiling
Genome-wide sequencing after damage can map repair synthesis tracts and mutations introduced by translesion synthesis. Proteomics can identify polymerase complexes recruited to damaged chromatin. These methods help distinguish error-free repair synthesis from mutagenic bypass.
Yeast and human cell genetic assays
Saccharomyces cerevisiae repair pathway assays have been used to define which pathways handle specific lesions and require repair synthesis. Human cell models complement yeast studies by testing polymerase requirements in a relevant disease context. Combining both systems strengthens causal inference about GO:0000731.
How CRISPR Can Be Used to Study GO:0000731 DNA synthesis involved in DNA repair
Knockout
CRISPR knockout is used to delete candidate genes and test whether they are required for DNA synthesis involved in DNA repair. Knockout of BRCA1, BRCA2, or translesion synthesis polymerases impairs repair synthesis and sensitizes cells to DNA-damaging agents. Knockout models are also used to define synthetic lethal interactions with repair synthesis defects.
Point Mutation
Point-mutation knock-in allows precise testing of residues that control polymerase recruitment, PCNA modification, or strand invasion. These models are useful when complete knockout is lethal or when a specific catalytic activity must be separated from a scaffold function. Point mutants can reveal whether a gene acts directly in repair synthesis or indirectly through pathway regulation.
Knock-in
Tagged knock-in of repair synthesis genes enables visualization and purification of endogenous complexes. Fluorescent or affinity tags on RAD51, PCNA, or translesion synthesis polymerases allow tracking of repair foci and interaction partners. Knock-in of disease-associated variants can model how patient mutations affect repair synthesis.
Overexpression
Overexpression models test whether increased levels of a repair synthesis gene drive chemoresistance or mutagenesis. Overexpression of translesion synthesis polymerases can increase bypass of DNA lesions and alter drug sensitivity. These models are useful for studying gain-of-function contributions to cancer therapy resistance.
How EDITGENE Supports DNA synthesis involved in DNA repair Research
Researchers studying DNA synthesis involved in DNA repair-related genes often need to determine whether a candidate gene is causally involved in the process or merely correlated with it. CRISPR-based models provide that causal link by allowing precise knockout, point mutation, knock-in, and overexpression of the genes that generate, extend, or regulate the broken 3' single-strand end during repair. EDITGENE supports this workflow with validated cell model engineering and screening services tailored to repair synthesis biology.
Contact EDITGENE today to design your custom CRISPR model for DNA synthesis involved in DNA repair research.
Frequently Asked Questions About DNA synthesis involved in DNA repair
What is GO:0000731 DNA synthesis involved in DNA repair?
GO:0000731 is a biological process defined as synthesis of DNA that proceeds from the broken 3' single-strand DNA end and uses the homologous intact duplex as the template.
What genes are involved in DNA synthesis involved in DNA repair?
Genes include polymerases such as POLH, POLI, POLK, REV1, and REV3L, as well as homologous recombination and fork remodeling factors such as RAD51, BRCA1, BRCA2, SMARCAL1, and ZRANB3.
Why is DNA synthesis involved in DNA repair important?
It restores missing DNA sequence after damage and determines whether repair is error-free or mutagenic, which affects genome stability, cancer risk, and therapy response.
How is DNA synthesis involved in DNA repair measured?
It can be measured by labeled nucleotide incorporation, repair foci imaging, live-cell fork imaging, genome-wide sequencing, and proteomics.
What is the difference between repair synthesis and translesion synthesis?
Repair synthesis uses an intact homologous duplex as the template, while translesion synthesis can bypass a lesion and may be error-prone.
Which diseases are linked to defects in DNA synthesis involved in DNA repair?
Defects are linked to cancer predisposition, chemoresistance, Fanconi anemia, and xeroderma pigmentosum variant.
How do CRISPR models help study DNA synthesis involved in DNA repair?
CRISPR knockout, point mutation, knock-in, and overexpression models allow causal testing of genes that generate, extend, or regulate the 3' single-strand end during repair.
What is the role of replication fork reversal in repair synthesis?
Fork reversal generates a 3' single-strand end that can prime DNA synthesis involved in DNA repair, linking fork remodeling to repair.
Can translesion synthesis polymerases perform repair synthesis?
Yes, translesion synthesis polymerases can extend from a 3' end during repair, including in interstrand crosslink repair, but they may introduce mutations.
What experimental models are used to study GO:0000731?
Common models include yeast genetic assays, human cell lines with labeled nucleotide incorporation, repair foci imaging, and CRISPR-engineered knockout or knock-in cells.
Conclusion
GO:0000731, DNA synthesis involved in DNA repair, defines the template-directed extension of a broken 3' single-strand DNA end using an intact homologous duplex. This process is essential for error-free repair, is coordinated with fork reversal, strand invasion, polymerase switching, and gap filling, and is directly linked to cancer predisposition, chemoresistance, and sensitivity to DNA-damaging agents. Studying it requires causal models, and CRISPR knockout, point-mutation, knock-in, overexpression, and library screening approaches provide the tools to dissect which genes truly execute or regulate repair synthesis.
References
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- 2. Du H et al.. 2019. Repair and translesion synthesis of O(6)-alkylguanine DNA lesions in human cells.. J Biol Chem 294(29):11144-11153 PMID: 31167778
- 3. Lehmann AR. 2011. DNA polymerases and repair synthesis in NER in human cells.. DNA Repair (Amst) 10(7):730-3 PMID: 21601536
- 4. Roy U et al.. 2016. Involvement of translesion synthesis DNA polymerases in DNA interstrand crosslink repair.. DNA Repair (Amst) 44:33-41 PMID: 27311543
- 5. Timson J. 1975. Hydroxyurea.. Mutat Res 32(2):115-32 PMID: 765790
- 6. Rodrigues GB et al.. 2021. Saccharomyces cerevisiae DNA repair pathways involved in repair of lesions induced by mixed ternary mononuclear Cu(II) complexes based on valproic acid with 1,10-phenanthroline or 2,2'- bipyridine ligands.. Mutat Res Genet Toxicol Environ Mutagen 868-869:503390 PMID: 34454693
- 7. Quinet A et al.. 2018. Filling gaps in translesion DNA synthesis in human cells.. Mutat Res Genet Toxicol Environ Mutagen 836(Pt B):127-142 PMID: 30442338
- 8. Spegg V et al.. 2024. Genome maintenance meets mechanobiology.. Chromosoma 133(1):15-36 PMID: 37581649
