GO:0070987 error-free translesion synthesis: Mechanism, Genes, Functions and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0070987 error-free translesion synthesis is a DNA damage tolerance process that uses specialized DNA polymerases to insert the correct nucleotide opposite a replication-blocking lesion without removing the lesion and without increasing the endogenous mutation level.
• In Saccharomyces cerevisiae, RAD30 encodes DNA polymerase eta, which incorporates two adenines across a thymine-thymine dimer in an error-free manner.
• Human translesion synthesis polymerases polκ and polη can perform error-free replication across specific DNA adducts such as N2-dG methyleugenol and estragole adducts.
• Error-free translesion synthesis is distinct from error-prone translesion synthesis, which can increase mutations and is associated with cancer and chemotherapy resistance.
• HMCES shields abasic sites in single-stranded DNA to maintain genome integrity and prevent error-prone processing.
• WRN and WRNIP1 ATPases impose high fidelity on translesion synthesis by Y-family DNA polymerases, highlighting regulatory layers that ensure error-free outcomes.
Description
Error-free translesion synthesis (GO:0070987) is a biological process that allows cells to replicate past DNA lesions without removing them and without elevating the endogenous mutation rate. This process is critical for genome maintenance because replication-blocking lesions, if left unrepaired, can cause replication fork stalling, double-strand breaks, and cell death. Unlike error-prone translesion synthesis, which uses low-fidelity polymerases and can introduce mutations, error-free translesion synthesis employs specialized DNA polymerases or replication complexes that insert the correct nucleotide opposite the lesion. The importance of this pathway is underscored by its conservation from yeast to humans and its role in preventing mutations that drive cancer and other diseases. Researchers study error-free translesion synthesis to understand how cells balance survival with genomic stability, and to identify therapeutic targets for cancer and DNA repair disorders.
error-free translesion synthesis At A Glance
| GO ID | GO:0070987 |
|---|---|
| GO term | error-free translesion synthesis |
| Ontology | biological_process |
| Synonym | none |
| Major function | Conversion of DNA-damage-induced single-stranded gaps into large molecular weight DNA after replication by using a specialized DNA polymerase or replication complex to insert a defined nucleotide across the lesion without increasing the endogenous mutation level |
| Organisms | Saccharomyces cerevisiae, Homo sapiens, and other eukaryotes |
| Key polymerases | DNA polymerase eta (RAD30 in S. cerevisiae), DNA polymerase kappa |
| Related processes | DNA damage tolerance, translesion synthesis, post-replication repair |
What Is GO:0070987?
Error-free translesion synthesis is the conversion of DNA-damage-induced single-stranded gaps into large molecular weight DNA after replication by using a specialized DNA polymerase or replication complex to insert a defined nucleotide across the lesion. This process does not remove the replication-blocking lesions but does not cause an increase in the endogenous mutation level. For example, in Saccharomyces cerevisiae, RAD30 encodes DNA polymerase eta, which incorporates two adenines across a thymine-thymine dimer without increasing the endogenous mutation level.
Why Is error-free translesion synthesis Important in Cell Biology?
Error-free translesion synthesis is essential for maintaining genome stability during DNA replication stress. By allowing replication to proceed past lesions without introducing mutations, it prevents the accumulation of mutations that can lead to cancer and other diseases. Defects in this pathway can cause hypersensitivity to DNA-damaging agents and are associated with cancer predisposition syndromes such as xeroderma pigmentosum. Understanding error-free translesion synthesis also has therapeutic implications, as cancer cells often rely on translesion synthesis to survive chemotherapy, making this pathway a target for sensitizing tumors to treatment.
• Prevents mutations by inserting correct nucleotides opposite DNA lesions.
• Allows replication fork progression past blocking lesions, avoiding fork collapse and double-strand breaks.
• Defects in error-free translesion synthesis are linked to cancer predisposition, including xeroderma pigmentosum.
• Plays a role in chemotherapy resistance, as cancer cells use translesion synthesis to bypass drug-induced DNA damage.
• Involved in the response to environmental carcinogens such as aryl hydrocarbons.
• Regulated by accessory proteins like WRN and WRNIP1 that ensure high fidelity.
• HMCES shields abasic sites to prevent error-prone processing and maintain genome integrity.
• Conserved from yeast to humans, making model organisms valuable for mechanistic studies.
• Potential target for cancer therapy to enhance the efficacy of DNA-damaging agents.
• Important for understanding the balance between DNA damage tolerance and mutagenesis.
What Happens During error-free translesion synthesis?
Lesion recognition and polymerase switching
In simple terms: The cell detects a DNA lesion that blocks replication and switches to a specialized polymerase that can copy past it.
During replication, DNA lesions such as thymine-thymine dimers or bulky adducts can stall the replicative polymerase. Error-free translesion synthesis begins with the recognition of these lesions and the recruitment of specialized translesion synthesis polymerases, such as DNA polymerase eta, to the stalled fork. In Saccharomyces cerevisiae, RAD30 encodes DNA polymerase eta, which is recruited to insert nucleotides across the lesion. This polymerase switching is tightly regulated to ensure that the correct polymerase is used for the specific lesion.
Nucleotide insertion across the lesion
In simple terms: The specialized polymerase adds the correct nucleotide opposite the damaged DNA base.
Once recruited, the translesion synthesis polymerase inserts a defined nucleotide across the lesion. For example, DNA polymerase eta incorporates two adenines across a thymine-thymine dimer, which is the correct pairing and thus error-free. Human polκ and polη have been shown to perform error-free replication across N2-dG methyleugenol and estragole DNA adducts. Similarly, translesion synthesis polymerases promote error-free replication through the minor-groove DNA adduct 3-deaza-3-methyladenine.
Extension and gap filling
In simple terms: After inserting the correct base, the polymerase extends the DNA to fill the gap and restore a normal DNA molecule.
Following nucleotide insertion, the translesion synthesis polymerase or another polymerase extends the DNA strand to fill the single-stranded gap, converting it into large molecular weight DNA. This extension step is crucial for completing replication and maintaining genome integrity. The process does not remove the lesion; instead, the lesion remains in the DNA and is bypassed. Accessory factors such as WRN and WRNIP1 ATPases impose high fidelity on this extension step by Y-family DNA polymerases.
Shielding of abasic sites by HMCES
In simple terms: A protein called HMCES protects abasic sites in single-stranded DNA to prevent them from causing mutations.
Abasic sites are common DNA lesions that can block replication. HMCES (5-hydroxymethylcytosine binding, ES cell-specific) maintains genome integrity by shielding abasic sites in single-strand DNA, preventing error-prone processing and promoting error-free outcomes. This shielding mechanism is an important part of the error-free translesion synthesis pathway, ensuring that abasic sites do not lead to mutations.
Regulation by REV7 and pathway choice
In simple terms: REV7 helps decide whether the cell uses error-free or error-prone translesion synthesis.
REV7 is a key regulator that directs DNA repair pathway choice, influencing whether translesion synthesis proceeds via error-free or error-prone mechanisms. REV7 interacts with multiple partners to coordinate the response to replication stress and DNA damage. This regulation is critical for maintaining the balance between survival and mutagenesis.
Key Genes Involved in GO:0070987 error-free translesion synthesis
The following genes and proteins are central to error-free translesion synthesis, based on published literature.
| Gene | Major Role | Research Relevance |
|---|---|---|
| RAD30 | Encodes DNA polymerase eta in S. cerevisiae; incorporates two adenines across thymine-thymine dimers | Model for studying error-free translesion synthesis mechanisms |
| POLH | Human DNA polymerase eta; performs error-free replication across certain adducts | Defects cause xeroderma pigmentosum variant; cancer research |
| POLK | Human DNA polymerase kappa; error-free replication across N2-dG methyleugenol and estragole adducts | Role in bypassing bulky DNA adducts |
| REV7 | Directs DNA repair pathway choice; regulates translesion synthesis | Target for cancer therapy and understanding chemotherapy resistance |
| HMCES | Shields abasic sites in single-stranded DNA to maintain genome integrity | Prevents error-prone processing of abasic sites |
| WRN | ATPase that imposes high fidelity on translesion synthesis by Y-family polymerases | Werner syndrome protein; role in genome stability |
| WRNIP1 | ATPase that collaborates with WRN to ensure high fidelity translesion synthesis | Regulator of translesion synthesis fidelity |
| PCNA | Sliding clamp that coordinates polymerase switching during translesion synthesis | Central hub for DNA damage tolerance |
| REV1 | Scaffold protein that recruits translesion synthesis polymerases | Coordinator of error-prone and error-free pathways |
| REV3 | Catalytic subunit of DNA polymerase zeta; involved in error-prone translesion synthesis | Contrasts with error-free pathways |
| REV7 (MAD2L2) | Subunit of polymerase zeta and regulator of pathway choice | Implicated in cancer and chemotherapy response |
| UBE2N | E2 ubiquitin-conjugating enzyme that modifies PCNA | Regulates polymerase switching |
| RAD18 | E3 ubiquitin ligase that monoubiquitinates PCNA | Key regulator of DNA damage tolerance |
| MUTYH | Involved in base excision repair; may influence lesion availability for translesion synthesis | Links to colorectal cancer |
| XPA | Nucleotide excision repair protein; defects cause xeroderma pigmentosum | Used to study translesion synthesis in repair-deficient backgrounds |
| XPC | Nucleotide excision repair protein; defects cause xeroderma pigmentosum | Model for studying translesion synthesis in repair-deficient backgrounds |
| POLI | Human DNA polymerase iota; Y-family polymerase | Potential role in translesion synthesis |
| POLZ | DNA polymerase zeta complex; error-prone translesion synthesis | Contrast with error-free pathways |
How Is error-free translesion synthesis Regulated?
Error-free translesion synthesis is regulated at multiple levels to ensure high fidelity and prevent mutagenesis. The process is coordinated by post-translational modifications, particularly monoubiquitination of PCNA by RAD18 and UBE2N, which promotes polymerase switching. REV7 directs DNA repair pathway choice, influencing whether error-free or error-prone translesion synthesis is used. Accessory ATPases such as WRN and WRNIP1 impose high fidelity on Y-family DNA polymerases during translesion synthesis. Additionally, HMCES shields abasic sites to prevent error-prone processing. These regulatory mechanisms ensure that error-free translesion synthesis is used preferentially when possible, maintaining genome stability.
error-free translesion synthesis and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| POLH | Xeroderma pigmentosum variant; skin cancer | POLH knockout or point-mutation cell lines; UV sensitivity assays |
| REV7 | Cancer progression and chemotherapy resistance | REV7 knockout or overexpression models; drug sensitivity assays |
| HMCES | Genome instability; potential cancer predisposition | HMCES knockout cells; abasic site repair assays |
| WRN | Werner syndrome; premature aging and cancer | WRN knockout or point-mutation models; translesion synthesis fidelity assays |
| XPA | Xeroderma pigmentosum; skin cancer | XPA knockout cells; UV mutagenesis studies |
Cancer and chemotherapy resistance
Error-free translesion synthesis is critical for cancer cells to survive DNA-damaging chemotherapy. Cancer cells often upregulate translesion synthesis polymerases to bypass drug-induced lesions, contributing to resistance. REV7, a key regulator of pathway choice, is implicated in cancer progression and chemotherapy response. Targeting error-free translesion synthesis could sensitize tumors to treatment.
Xeroderma pigmentosum and skin cancer
Xeroderma pigmentosum (XP) is a genetic disorder caused by defects in nucleotide excision repair, leading to extreme sensitivity to UV radiation and a high risk of skin cancer. In XP patients, error-free translesion synthesis is critical for bypassing UV-induced lesions such as thymine-thymine dimers. Genomic mutation landscapes in skin cancers from XP patients reveal distinct mutational signatures that reflect the interplay between defective repair and translesion synthesis.
Environmental carcinogenesis
Error-free and error-prone translesion synthesis over DNA adducts formed by environmental carcinogens such as aryl hydrocarbons (3-nitrobenzanthrone and 4-aminobiphenyl) can influence mutation spectra and cancer risk. Understanding how cells process these adducts via translesion synthesis is important for assessing carcinogen exposure and developing prevention strategies.
From error-free translesion synthesis-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| Does loss of POLH increase mutation frequency after UV exposure? | POLH knockout cell line (e.g., human fibroblasts) |
| Does a specific point mutation in REV7 alter pathway choice? | REV7 point-mutation knock-in cell line |
| Can overexpression of WRNIP1 enhance error-free translesion synthesis? | WRNIP1 overexpression cell line |
| Does HMCES shield abasic sites in vivo? | HMCES knockout or tagged knock-in cells |
| What is the role of RAD30 in error-free bypass of thymine-thymine dimers? | S. cerevisiae RAD30 knockout or point-mutation strains |
| Does POLK perform error-free replication across specific adducts? | POLK knockout or overexpression human cell lines |
How to Study the error-free translesion synthesis Process
| Method | What It Measures | Typical Application |
|---|---|---|
| Site-specific adduct bypass assay | Efficiency and fidelity of translesion synthesis across a defined lesion | Studying error-free vs error-prone bypass |
| Whole-genome sequencing | Mutational signatures and burden | Linking translesion synthesis defects to cancer |
| CRISPR knockout | Loss-of-function effects on DNA damage sensitivity | Validating gene function in error-free translesion synthesis |
| CRISPR knock-in | Effects of specific mutations on pathway choice | Modeling patient variants |
| In vitro polymerase fidelity assay | Nucleotide incorporation accuracy | Testing accessory factor influence |
| Co-immunoprecipitation | Protein-protein interactions | Identifying regulatory complexes |
| UV sensitivity assay | Cell survival after DNA damage | Assessing repair and tolerance capacity |
| Abasic site shielding assay | HMCES binding and protection | Studying genome integrity mechanisms |
Site-specific DNA adduct creation and translesion synthesis assays
To study error-free translesion synthesis, researchers use site-specifically created DNA adducts (e.g., aryl hydrocarbon adducts) in oligonucleotides or plasmids, followed by replication in cell extracts or cells. This allows measurement of bypass efficiency and fidelity. Such assays can distinguish error-free from error-prone outcomes.
Mutational signature analysis and genomic sequencing
Genomic mutation landscape analysis, such as whole-exome or whole-genome sequencing of skin cancers from xeroderma pigmentosum patients, can reveal mutational signatures associated with defective repair and translesion synthesis. This approach helps link specific polymerases to mutation patterns.
CRISPR-based knockout and knock-in models
CRISPR/Cas9 can be used to generate knockout, point-mutation, or knock-in cell lines for genes involved in error-free translesion synthesis (e.g., POLH, REV7, HMCES). These models enable functional studies of gene variants and their impact on DNA damage tolerance.
Protein interaction and fidelity assays
In vitro translesion synthesis assays using purified Y-family polymerases and accessory factors (e.g., WRN, WRNIP1) can measure fidelity and bypass efficiency. Co-immunoprecipitation and proximity labeling can identify interaction partners.
How CRISPR Can Be Used to Study GO:0070987 error-free translesion synthesis
Knockout
CRISPR knockout of genes such as POLH, REV7, or HMCES can reveal their essential roles in error-free translesion synthesis. For example, POLH knockout cells show increased UV sensitivity and mutagenesis, mimicking xeroderma pigmentosum variant. Knockout of HMCES leads to genome instability due to unprotected abasic sites.
Point Mutation
Point mutations in genes like REV7 can be introduced to study their impact on DNA repair pathway choice. Such models help dissect the molecular determinants of error-free versus error-prone translesion synthesis. Similarly, point mutations in POLH can model patient variants with defective error-free bypass.
Knock-in
Knock-in of tagged versions of proteins (e.g., HMCES-GFP) allows visualization and biochemical isolation of complexes involved in error-free translesion synthesis. Knock-in of disease-associated alleles can model their effects on DNA damage tolerance.
Overexpression
Overexpression of error-free translesion synthesis components, such as WRNIP1 or POLK, can test whether increased levels enhance fidelity or bypass efficiency. This approach can also reveal dominant-negative effects or saturation of regulatory pathways.
How EDITGENE Supports error-free translesion synthesis Research
Researchers studying error-free translesion synthesis-related genes often need to determine whether a candidate gene is causally involved in DNA damage tolerance, whether a specific mutation alters fidelity, or whether overexpression changes cellular sensitivity to DNA-damaging agents. EDITGENE provides comprehensive CRISPR-based services to address these questions with precision and reproducibility.
Contact EDITGENE today to design your custom CRISPR model for error-free translesion synthesis research.
Frequently Asked Questions About error-free translesion synthesis
What is error-free translesion synthesis?
Error-free translesion synthesis (GO:0070987) is a DNA damage tolerance process that uses specialized DNA polymerases to insert the correct nucleotide across a replication-blocking lesion without removing the lesion and without increasing the endogenous mutation level.
What genes are involved in error-free translesion synthesis?
Key genes include RAD30 (S. cerevisiae), POLH, POLK, REV7, HMCES, WRN, and WRNIP1.
How does error-free translesion synthesis differ from error-prone translesion synthesis?
Error-free translesion synthesis inserts the correct nucleotide and does not increase mutations, while error-prone translesion synthesis can introduce mutations and is associated with cancer and drug resistance.
What is the role of DNA polymerase eta in error-free translesion synthesis?
DNA polymerase eta (encoded by RAD30 in yeast and POLH in humans) incorporates two adenines across a thymine-thymine dimer, which is error-free.
Which diseases are linked to defects in error-free translesion synthesis?
Defects are linked to xeroderma pigmentosum and increased skin cancer risk, as well as potential cancer predisposition and chemotherapy resistance.
How can I study error-free translesion synthesis using CRISPR?
CRISPR knockout, point mutation, knock-in, and overexpression models can be used to test gene function, fidelity, and cellular sensitivity to DNA-damaging agents.
What is the role of HMCES in error-free translesion synthesis?
HMCES shields abasic sites in single-stranded DNA to maintain genome integrity and prevent error-prone processing.
How is error-free translesion synthesis regulated?
It is regulated by PCNA monoubiquitination, REV7 pathway choice, and accessory ATPases such as WRN and WRNIP1 that ensure high fidelity.
What experimental models are used to study error-free translesion synthesis?
Models include S. cerevisiae RAD30 mutants, human cell lines with POLH or REV7 knockouts, and site-specific adduct bypass assays.
Why is error-free translesion synthesis important for cancer research?
Cancer cells rely on translesion synthesis to survive chemotherapy; targeting error-free pathways could sensitize tumors to DNA-damaging treatments.
Conclusion
Error-free translesion synthesis (GO:0070987) is a vital DNA damage tolerance mechanism that allows cells to replicate past lesions without introducing mutations. Its importance spans genome stability, cancer predisposition, and chemotherapy resistance. Key genes such as POLH, POLK, REV7, HMCES, WRN, and WRNIP1 orchestrate this process with high fidelity. Understanding the molecular details of error-free translesion synthesis offers opportunities for therapeutic intervention and biomarker discovery. EDITGENE provides the CRISPR tools and services needed to accelerate research in this field.
References
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- 2. Deshmukh PU et al.. 2023. Human Translesion Synthesis Polymerases polκ and polη Perform Error-Free Replication across N(2)-dG Methyleugenol and Estragole DNA Adducts.. Biochemistry 62(16):2391-2406 PMID: 37486230
- 3. Xu X et al.. 2015. Error-free DNA-damage tolerance in Saccharomyces cerevisiae.. Mutat Res Rev Mutat Res 764:43-50 PMID: 26041265
- 4. Yoon JH et al.. 2017. Translesion synthesis DNA polymerases promote error-free replication through the minor-groove DNA adduct 3-deaza-3-methyladenine.. J Biol Chem 292(45):18682-18688 PMID: 28939775
- 5. Mohni KN et al.. 2019. HMCES Maintains Genome Integrity by Shielding Abasic Sites in Single-Strand DNA.. Cell 176(1-2):144-153.e13 PMID: 30554877
- 6. Yurchenko AA et al.. 2023. Genomic mutation landscape of skin cancers from DNA repair-deficient xeroderma pigmentosum patients.. Nat Commun 14(1):2561 PMID: 37142601
- 7. Clairmont CS et al.. 2021. REV7 directs DNA repair pathway choice.. Trends Cell Biol 31(12):965-978 PMID: 34147298
- 8. Yoon JH et al.. 2025. WRN and WRNIP1 ATPases impose high fidelity on translesion synthesis by Y-family DNA polymerases.. Elife 14 PMID: 40900148
