HUMAN EXONUCLEASE-I INTERACTS WITH THE MISMATCH REPAIR PROTEIN HMSH21

DNA mismatch repair (MMR) plays a vital role in the faithful replicati on of DNA, and its inactivation leads to a mutator phenotype that has been associated with the common cancer susceptibility syndrome Heredit ary Non-Polyposis Colorectal Cancer (HNPCC). Here, we report on a nove l human exonuclease (hExoI) that is related to the yeast exonuclease 1 . The hExoI cDNA comprises 2541 bp, which code for a M-r 94,000 protei n that appears to be highly expressed in testis tissue and at very low levels in other tissues. The hExoI gene has 14 exons and is located o n chromosome 1q43, as determined by fluorescence in situ hybridization and radiation hybrid mapping. hExoI was found to interact strongly wi th the human MMR protein hMSH2, suggesting its involvement in the MMR process and/or DNA recombination.