A core promoter and a frequent single-nucleotide polymorphism of the mismatch repair gene hMLH1

The hMLH1 gene encodes a protein that is involved in the DNA mismatch repai r system. The coding region of the hMLH1 gene has been known to be mutated in a subset of patients with hereditary nonpolyposis colorectal cancer (HNP CC). Our current research characterized the promoter region of the hMLH1 ge ne and searched for mutations correlating to HNPCC.:Utilizing the oligo-cap ping method, major transcription start sites of the hMLH1 gene were mapped at two locations. The core promoter region of about 180 bp was determined b y the luciferase assay of serial deletion mutants. Although we did not find any pathogenic mutation in the hMLH1 promoter region by PCR-SSCP, we found : a single-nucleotide polymorphism at position -93 nt from the adenine resi due of the start codon. By PCR-RFLP analysis with Pvu II for this polymorph ism we detected LOH in four tumors from three patients. An easy detection o f this polymorphism with PCR-RFLP and high incidence (similar to 50%) of in formative cases make this polymorphism a suitable marker for the detection of hMLH1 allelic losses. (C) 1999 Academic Press.