rs13181 — ERCC2 Lys751Gln

Missense variant in the XPD helicase that reduces nucleotide excision repair capacity, increasing susceptibility to DNA damage from UV, tobacco smoke, and environmental carcinogens

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ERCC2 Lys751Gln — When the DNA Repair Crew Works at Reduced Capacity

Your genome is under constant assault. Every day, ultraviolet radiation, tobacco smoke, air pollution, and industrial chemicals bombard your DNA with bulky chemical modifications called adducts11 adducts
large chemical groups that bind to DNA bases, physically distorting the double helix and blocking replication and transcription. Left unrepaired, these lesions cause mutations that accumulate over a lifetime — the molecular basis of genomic aging and carcinogenesis.

ERCC2 (also known as XPD) is the helicase engine at the core of nucleotide excision repair (NER)22 nucleotide excision repair (NER)
the primary DNA repair pathway for removing bulky adducts, operating in two modes: global genome NER for random lesions throughout the genome, and transcription-coupled NER for damage blocking active genes. The rs13181 variant changes a single amino acid at position 751 — lysine (Lys) to glutamine (Gln) — in a region of the protein that mediates interaction with the CAK kinase subcomplex33 CAK kinase subcomplex
a three-protein module (CDK7, cyclin H, MAT1) within the TFIIH transcription and repair complex; ERCC2 bridges CAK to the core TFIIH structure. The result is reduced helicase activity and measurably impaired DNA repair.

The Mechanism

ERCC2/XPD functions as a 5'-to-3' DNA helicase within the ten-subunit TFIIH complex. During NER, TFIIH unwinds roughly 30 base pairs of DNA around a lesion so that excision enzymes can cut out the damaged segment. The Gln751 substitution falls in the C-terminal domain where XPD contacts the CAK subcomplex and other TFIIH components; disrupting this interface reduces the helicase's opening efficiency.

Functional assays confirm the biochemical prediction. Sha Xiao et al. (2016)44 Sha Xiao et al. (2016)
The ERCC2/XPD Lys751Gln polymorphism affects DNA repair of benzo[a]pyrene induced damage, tested in an in vitro model. Toxicol In Vitro transfected ERCC2-deficient CHO cells with either the Lys751 or Gln751 cDNA and challenged them with benzo[a]pyrene (the predominant carcinogen in tobacco smoke). Cells expressing Gln751 showed significantly greater DNA strand breaks, slower repair kinetics, and higher cellular toxicity — directly demonstrating that the variant reduces NER capacity for a real-world environmental carcinogen.

A parallel study by Zhang et al. (2017)55 Zhang et al. (2017)
ERCC2/XPD Lys751Gln alter DNA repair efficiency of platinum-induced DNA damage through P53 pathway. Chem Biol Interact found the same pattern for cisplatin-induced DNA crosslinks: Gln751 cells repaired platinum adducts less efficiently, accumulated more S-phase arrest, and showed altered p53 signaling compared to Lys751 cells.

The Evidence

The clinical consequence of impaired NER accumulates over a lifetime. Multiple large meta-analyses have examined rs13181 across cancer types:

Lung cancer: Zhan P et al. (2010)66 Zhan P et al. (2010)
ERCC2/XPD Lys751Gln and Asp312Asn gene polymorphism and lung cancer risk: a meta-analysis involving 22 case-control studies. J Thorac Oncol pooled 22 case-control studies and found that Gln/Gln homozygotes (GG on the plus strand) have a 26% higher lung cancer risk versus Lys/Lys (OR 1.26, 95% CI 1.12–1.42). The elevated risk was consistent across Caucasian and, in most models, Asian subgroups.

Bladder cancer: Meta-analyses have also found modestly elevated bladder cancer risk in Gln carriers, with both heterozygotes and homozygotes showing elevated risk — consistent with a codominant effect. Notably, the bladder cancer association is stronger in smokers, a direct mechanistic consequence of tobacco carcinogens overwhelming impaired NER.

Head, neck, and other cancers: Associations have been reported for squamous cell carcinoma of the head and neck, glioma, esophageal cancer, and nasopharyngeal carcinoma, though the effect sizes are modest (OR 1.1–1.4) and consistency varies by population.

Longevity: Intriguingly, a Polish centenarian study (Polosak et al., Biogerontology 2010)77 (Polosak et al., Biogerontology 2010) found that among 149 centenarians (mean age 101), both homozygous genotypes (Lys/Lys and Gln/Gln in coding notation, corresponding to TT and GG on the plus strand) were less frequent than in young controls. The heterozygous Lys/Gln (TG) genotype appeared enriched in extreme survivors. The same study found that XPD mRNA expression decreases significantly with age — lower NER gene expression in elderly tissues may represent an adaptive response, not pure deterioration. The longevity finding requires replication in larger cohorts but adds biological nuance to the simple "more repair = better" narrative.

Gene-environment interaction: The variant matters most in the context of carcinogen exposure. Affatato et al. (2004)88 Affatato et al. (2004)
Effect of XPD/ERCC2 polymorphisms on chromosome aberration frequencies in smokers found elevated chromosome aberration rates in smokers carrying variant alleles of a related ERCC2 variant (rs1799793, Asp312Asn) — not rs13181 (Lys751Gln) directly. The gene-environment interaction principle nonetheless supports that reduced NER capacity amplifies carcinogen-induced DNA damage, and reducing carcinogen exposure is especially impactful for Gln carriers.

Practical Actions

The Gln allele reduces your cellular repair throughput for bulky DNA adducts — this does not cause cancer, but it means that adducts accumulate faster and persist longer when encountered. The implications are dose-dependent: more carcinogen exposure translates into greater relative disadvantage compared to Lys/Lys individuals.

For Gln carriers, the highest-leverage interventions target carcinogen exposure (avoidance) and cellular antioxidant defenses (supplementation). Monitoring should focus on cancer-related screenings appropriate for the tissues most exposed to relevant carcinogens.

Interactions

ERCC2 carries a second well-studied variant, Asp312Asn (rs1799793), also in a conserved functional domain. Both variants have been associated with lung cancer and bladder cancer in overlapping meta-analyses. Some studies suggest that carrying risk alleles at both positions amplifies cancer susceptibility beyond either alone, particularly for lung and head-and-neck cancer in the context of tobacco exposure. This interaction is documented primarily in observational studies and warrants compound analysis when both genotypes are available.

Other relevant NER pathway genes include ERCC1 (the endonuclease partner of XPD in the NER complex) and XRCC1 (base excision repair). Multi-variant risk scores combining rs13181 with variants in these genes are under active investigation but are not yet at the level of actionable clinical guidance.

Genotype Interpretations

What each possible genotype means for this variant.

TT Full Repair Capacity Normal

Normal ERCC2 helicase activity with typical nucleotide excision repair capacity

You have two copies of the Lys751 (T) allele, the reference form of ERCC2. Your XPD helicase protein has standard activity within the TFIIH complex, giving you typical capacity to unwind DNA around bulky adducts caused by UV radiation, tobacco carcinogens, and environmental chemicals. Functional assays confirm that Lys751/Lys751 cells repair benzo[a]pyrene and cisplatin-induced DNA damage more efficiently than Gln751-carrying cells. About 46% of people globally share this genotype; in Europeans it is slightly less common (~41% TT) because the G allele runs at higher frequency in European populations.

GT Intermediate Repair Capacity Intermediate

One copy of the reduced-activity Gln751 variant with modestly impaired DNA repair

The Gln751 substitution reduces the efficiency with which ERCC2/XPD unwinds DNA around bulky adducts, slowing the overall NER process. In heterozygotes, the remaining Lys751 allele partially compensates, but repair throughput is still reduced. The clinical consequence is dose-dependent: in non-smokers with limited carcinogen exposure, the risk differential vs TT individuals is small. In smokers or those with high occupational carcinogen exposure, the relative disadvantage of reduced NER is amplified — consistent with the gene-environment interaction data showing greatest excess risk in heavy smokers.

The longevity data from the Polish centenarian cohort are intriguing: TG heterozygotes appeared enriched among centenarians relative to both TT and GG homozygotes (though the study was modest in size). Whether this reflects a genuine heterozygote advantage for extreme longevity or is a chance finding requires replication.

GG Reduced Repair Capacity Reduced

Two copies of the reduced-activity Gln751 variant with significantly impaired nucleotide excision repair

The Gln751 substitution in both copies of ERCC2 eliminates the residual compensation provided by one Lys751 allele. NER operates at the lowest end of normal variation, meaning bulky DNA adducts — from UV, tobacco, air pollution, and other environmental sources — take longer to remove and are more likely to persist through cell division, increasing the probability of replication errors (mutations).

The cancer risk elevation documented in meta-analyses (OR 1.17–1.26 for lung cancer in the homozygous recessive model) reflects lifetime accumulation of this repair deficit. The association is strongest in tissues with the highest carcinogen exposure: lung (tobacco smoke, air pollution), bladder (urinary concentration of tobacco metabolites and aromatic amines), and head-and-neck mucosa (tobacco, alcohol, HPV).

It is important to contextualize the risk: an OR of 1.2–1.3 means a modest percentage increase over baseline cancer risk, not a guarantee of disease. Environmental factors account for the majority of variance in cancer risk even in GG individuals. However, the repair deficit is real, measurable, and actionable — carcinogen avoidance and antioxidant support are more impactful for GG individuals than for TT individuals precisely because their cellular repair buffer is thinner.

The centenarian study noting lower GG frequency among extreme survivors (versus young controls) aligns with the concept of cumulative genomic instability as a longevity liability — though this single study is insufficient for strong conclusions.