The interaction of the human MutL homologues in hereditary nonpolyposis colon cancer.
Germline mutations in two human mismatch repair (MMR) genes, hMSH2 and hMLH1, appear to account for approximately 70% of the common cancer susceptibility syndrome hereditary nonpolyposis colorectal cancer (HNPCC). Although the hMLH1 protein has been found to copurify with another MMR protein hPMS2 as a heterodimer, their function in MMR is unknown. In this study, we have identified the physical interaction regions of both hMLH1 with hPMS2. We then examined the effects of hMLH1 missense alterations found in HNPCC kindreds for their interaction with hPMS2. Four of these missense alterations (L574P, K616Delta, R659P, and A681T) displayed >95% reduction in binding to hPMS2. Two additional missense alterations (K618A and K618T) displayed a >85% reduction in binding to hPMS2, whereas three missense alterations (S44F, V506A, and E578G) displayed 25-65% reduction in binding to hPMS2. Interestingly, two HNPCC missense alterations (Q542L and L582V) contained within the consensus interaction region displayed no effect on interaction with hPMS2, suggesting that they may affect other functions of hMLH1. These data confirm that functional deficiencies in the interaction of hMLH1 with hPMS2 are associated with HNPCC as well as suggest that other unknown functional alteration of the human MutL homologues may lead to tumorigenesis in HNPCC kindreds.
Guerrette
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Genetics and Molecular Biology Program, Department of Microbiology and Immunology, Kimmel Cancer Center, Thomas Jefferson University, Philadelphia, Pennsylvania 19107, USA.
Acharya
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Fishel
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D048868:Adaptor Proteins, Signal Transducing; D000251:Adenosine Triphosphatases; D001426:Bacterial Proteins / Q000235:genetics*; D002352:Carrier Proteins; D003123:Colorectal Neoplasms, Hereditary Nonpolyposis / Q000235:genetics*; D004260:DNA Repair; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D000070957:MutL Protein Homolog 1; D000070956:MutL Proteins; D051718:MutS Homolog 2 Protein; D009154:Mutation; D009363:Neoplasm Proteins / Q000235:genetics*; D009687:Nuclear Proteins; D011518:Proto-Oncogene Proteins / Q000235:genetics*; D012689:Sequence Homology, Nucleic Acid
D048868:Adaptor Proteins, Signal Transducing; D001426:Bacterial Proteins; D002352:Carrier Proteins; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; C501486:MLH1 protein, human; C074770:MutL protein, E coli; D009363:Neoplasm Proteins; D009687:Nuclear Proteins; D011518:Proto-Oncogene Proteins; D000251:Adenosine Triphosphatases; C497172:MSH2 protein, human; D000070957:MutL Protein Homolog 1; D000070956:MutL Proteins; D051718:MutS Homolog 2 Protein