Identification of mismatch repair protein complexes in HeLa nuclear extracts and their interaction with heteroduplex DNA.
Deficiencies in DNA mismatch repair (MMR) have been found in hereditary colon cancers (hereditary non-polyposis colon cancer, HNPCC) as well as in sporadic cancers, illustrating the importance of MMR in maintaining genomic integrity. We have examined the interactions of specific mismatch repair proteins in human nuclear extracts. Western blot and co-immunoprecipitation studies indicate two complexes as follows: one consisting of hMSH2, hMSH6, hMLH1, and hPMS2 and the other consisting of hMSH2, hMSH6, hMLH1, and hPMS1. These interactions occur without the addition of ATP. Furthermore, the protein complexes specifically bind to mismatched DNA and not to a similar homoduplex oligonucleotide. The protein complex-DNA interactions occur primarily through hMSH6, although hMSH2 can also become cross-linked to the mismatched substrate when not participating in the MMR protein complex. In the presence of ATP the binding of hMSH6 to mismatched DNA is decreased. In addition, hMLH1, hPMS2, and hPMS1 no longer interact with each other or with the hMutSalpha complex (hMSH2 and hMSH6). However, the ability of hMLH1 to co-immunoprecipitate mismatched DNA increases in the presence of ATP. This interaction is dependent on the presence of the mismatch and does not appear to involve a direct binding of hMLH1 to the DNA.
Matton
N
N
Department of Biological Sciences/Biomedical Program, University of Alaska, Anchorage, Alaska 99508, USA.
Simonetti
J
J
Williams
K
K
D048868:Adaptor Proteins, Signal Transducing; D020137:Base Pair Mismatch; D002352:Carrier Proteins; D002467:Cell Nucleus / Q000378:metabolism*; D004247:DNA / Q000302:isolation & purification / Q000378:metabolism*; D004260:DNA Repair; D004268:DNA-Binding Proteins / Q000302:isolation & purification / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D000070957:MutL Protein Homolog 1; D000070956:MutL Proteins; D051718:MutS Homolog 2 Protein; D009363:Neoplasm Proteins / Q000302:isolation & purification / Q000378:metabolism*; D009687:Nuclear Proteins; D009692:Nucleic Acid Heteroduplexes / Q000302:isolation & purification / Q000378:metabolism*; D011485:Protein Binding; D011518:Proto-Oncogene Proteins / Q000302:isolation & purification / Q000378:metabolism*; D014466:Ultraviolet Rays
D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; D004268:DNA-Binding Proteins; C094443:G-T mismatch-binding protein; C501486:MLH1 protein, human; D009363:Neoplasm Proteins; D009687:Nuclear Proteins; D009692:Nucleic Acid Heteroduplexes; C088996:PMS1 protein, human; D011518:Proto-Oncogene Proteins; D004247:DNA; C497172:MSH2 protein, human; D000070957:MutL Protein Homolog 1; D000070956:MutL Proteins; D051718:MutS Homolog 2 Protein