DNA gap position within guanine runs shapes mutation patterns in mismatch-repair-deficient cancers

A preprint posted to bioRxiv on 20 October 2026 reports that in mismatch repair deficient gastric, colorectal and endometrial cancers, G>T mutations inside guanine runs are not randomly placed. Instead, they are markedly enriched at the 5' guanine of the run, with enrichment scores of 0.86 to 0.87, and strongly depleted at the 3' guanine, scoring 0.05 to 0.08. The work suggests that the local sequence context, specifically position within the guanine run, imprints where mutations arise when mismatch repair is lost, offering a structural explanation for patterns already observed in these tumor types. The findings come from a preprint and have not yet been peer reviewed; independent validation and mechanistic follow-up remain outstanding.

Written by a model from the reports · updated 3 hours ago