A carboxy terminal domain of the hMSH-2 gene product is sufficient for binding specific mismatched oligonucleotides

The human MSH-2 gene product is a member of a highly conserved family of proteins which are involved in post-replication mismatch repair. hMSH-2 is homologous to Escherichia coli (E. coli) MutS and Sacchromyces cerevisiae MSH-1 and MSH-2 proteins, which recognise heteroduplex DNA at the sites of all single base mismatches and deletions or insertions up to 4 base pairs. hMSH-2 is one of the hereditary non-polyposis colorectal cancer (HNPCC) tumor suppressor genes, and maps to human chromosome 2p16. Alterations in the coding region of the hMSH-2 gene result in a mutator phenotype with marked instability of microsatellite sequences, indicative of a deficiency in DNA repair. It has been shown that purified hMSH-2 binds specifically to nucleotide mismatches in double-stranded DNA. Here we demonstrate that a region of high homology between the members of this class of proteins contains a type A nucleotide binding site consensus sequence which has ATPase activity and is sufficient to bind DNA containing specific mismatched residues.