title: Dimerization of MLH1 and PMS2 limits nuclear localization of MutLalpha.
abstract: DNA mismatch repair maintains genomic stability by detecting and correcting mispaired DNA sequences and by signaling cell death when DNA repair fails. The mechanism by which mismatch repair coordinates DNA damage and repair with cell survival or death is not understood, but it suggests the need for regulation. Since the functions of mismatch repair are initiated in the nucleus, we asked whether nuclear transport of MLH1 and PMS2 is limiting for the nuclear localization of MutLalpha (the MLH1-PMS2 dimer). We found that MLH1 and PMS2 have functional nuclear localization signals (NLS) and nuclear export sequences, yet nuclear import depended on their C-terminal dimerization to form MutLalpha. Our studies are consistent with the idea that dimerization of MLH1 and PMS2 regulates nuclear import by unmasking the NLS. Limited nuclear localization of MutLalpha may thus represent a novel mechanism by which cells fine-tune mismatch repair functions. This mechanism may have implications in the pathogenesis of hereditary non-polyposis colon cancer.
authors.affiliation: Transplantation Biology, Mayo Clinic, Rochester, Minnesota 55905, USA.
authors.forename: Xiaosheng
authors.initials: X
authors.lastname: Wu
authors.forename: Jeffrey L
authors.initials: JL
authors.lastname: Platt
authors.forename: Marilia
authors.initials: M
authors.lastname: Cascalho
mesh_terms: D021581:Active Transport, Cell Nucleus / Q000502:physiology; D048868:Adaptor Proteins, Signal Transducing; D000251:Adenosine Triphosphatases / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D020137:Base Pair Mismatch; D001483:Base Sequence; D002352:Carrier Proteins; D002467:Cell Nucleus / Q000235:genetics / Q000378:metabolism*; D004260:DNA Repair / Q000502:physiology; D045643:DNA Repair Enzymes; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D019281:Dimerization; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D051379:Mice; D000070976:Mismatch Repair Endonuclease PMS2; D008969:Molecular Sequence Data; D000070957:MutL Protein Homolog 1; D000070956:MutL Proteins; D009363:Neoplasm Proteins / Q000235:genetics / Q000378:metabolism*; D019913:Nuclear Localization Signals; D009687:Nuclear Proteins
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; C501486:MLH1 protein, human; C501485:Mlh1 protein, mouse; C074770:MutL protein, E coli; D009363:Neoplasm Proteins; D019913:Nuclear Localization Signals; D009687:Nuclear Proteins; D000251:Adenosine Triphosphatases; C094934:PMS2 protein, human; C499533:Pms2 protein, mouse; D000070976:Mismatch Repair Endonuclease PMS2; D000070957:MutL Protein Homolog 1; D000070956:MutL Proteins; D045643:DNA Repair Enzymes