title: Identification of a second MutL DNA mismatch repair complex (hPMS1 and hMLH1) in human epithelial cells.
abstract: Deficiencies of MutL DNA mismatch repair-complex proteins (hMLH1, hPMS2, and hPMS1) typically result in microsatellite instability in human cancers. We examined the association patterns of MutL proteins in human epithelial cancer cell lines with (HCT-116, N87, SNU-1, and SNU-638) and without microsatellite instability (HeLa, AGS, KATO-III, and SNU-16). The analysis of hMLH1, hPMS2, and hPMS1 was performed using Northern blot, Western blot, and co-immunoprecipitation studies. Our data provide evidence that MutL proteins form two different complexes, MutL-alpha (hPMS2 and hMLH1) and MutL-beta (hPMS1 and hMLH1). Gastric and colorectal cancer cells lines with microsatellite instability lacked detectable hMLH1. Decreased levels of hMLH1 protein were associated with markedly reduced levels of hPMS2 and hPMS1 proteins, but the RNA levels of hPMS1 and hPMS2 were normal. In this study, we describe the association of hPMS1 with hMLH1 as a heterodimer, in human cells. Furthermore, normal levels of hMLH1 protein appear to be important in maintaining normal levels of hPMS1 and hPMS2 proteins.
authors.affiliation: Departments of Medicine and Pathology, Veterans Affairs Medical Center and Baylor College of Medicine, Houston, Texas 77030, USA.
authors.forename: W K
authors.initials: WK
authors.lastname: Leung
authors.forename: J J
authors.initials: JJ
authors.lastname: Kim
authors.forename: L
authors.initials: L
authors.lastname: Wu
authors.forename: J L
authors.initials: JL
authors.lastname: Sepulveda
authors.forename: A R
authors.initials: AR
authors.lastname: Sepulveda
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D000251:Adenosine Triphosphatases; D020137:Base Pair Mismatch / Q000235:genetics*; D002352:Carrier Proteins / Q000235:genetics* / Q000378:metabolism; D004260:DNA Repair / Q000235:genetics*; D045643:DNA Repair Enzymes; D004268:DNA-Binding Proteins; D019281:Dimerization; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D018895:Microsatellite Repeats / Q000235:genetics; D000070976:Mismatch Repair Endonuclease PMS2; D000070957:MutL Protein Homolog 1; D000070956:MutL Proteins; D009363:Neoplasm Proteins / Q000235:genetics* / Q000378:metabolism; D009687:Nuclear Proteins; D011233:Precipitin Tests; D011506:Proteins / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D014407:Tumor Cells, Cultured
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; D004268:DNA-Binding Proteins; C501486:MLH1 protein, human; D009363:Neoplasm Proteins; D009687:Nuclear Proteins; C088996:PMS1 protein, human; D011506:Proteins; D012333:RNA, Messenger; D000251:Adenosine Triphosphatases; C094934:PMS2 protein, human; D000070976:Mismatch Repair Endonuclease PMS2; D000070957:MutL Protein Homolog 1; D000070956:MutL Proteins; D045643:DNA Repair Enzymes