title: A novel function of protein kinase B as an inducer of the mismatch repair gene hPMS2 degradation.
abstract: Human DNA mismatch repair (MMR) proteins correct DNA errors, which normally occur during DNA replication. Defects of MMR genes result in genomic instability and carcinogenesis. However, the mechanism of MMR proteins regulation has not yet been clearly explored, especially for the member of MutL-related protein, human post meiotic segregation increased 2 (hPMS2). In this study, an inverse correlation between hPMS2 level and activated Akt was detected in nine tumor cell lines by western blot. The negative regulation of hPMS2 expression by activated Akt was further verified by functional experiments manipulating Akt activity using siRNA targeting Akt, Akt Inhibitor I, Akt/PKB Signaling Inhibitor-2 (API-2) and Insulin-like Growth Factor-I (IGF-1). In addition, protein complex immunoprecipitation assays and protein stability assays using cycloheximide revealed that activated Akt (P-Akt1 S473) could bind to hPMS2 directly and induce hPMS2 degradation. Moreover, results of immunofluorescence assays showed blocking Akt activity resulted in accumulation of hPMS2 protein in nucleus. These observations indicate that activated Akt is the upstream signaling regulating hPMS2 expression, stability and nuclear localization, providing a novel insight into the regulation of hPMS2 in cancer cells.
authors.affiliation: Department of Obstetrics and Gynecology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430022, PR China.
authors.forename: Jinghui
authors.initials: J
authors.lastname: Jia
authors.forename: Yuan
authors.initials: Y
authors.lastname: Zhang
authors.forename: Jing
authors.initials: J
authors.lastname: Cai
authors.forename: Junjie
authors.initials: J
authors.lastname: Wang
authors.forename: Hui
authors.initials: H
authors.lastname: Ding
authors.forename: Jun
authors.initials: J
authors.lastname: Zhou
authors.forename: Fang
authors.initials: F
authors.lastname: Fang
authors.forename: Zehua
authors.initials: Z
authors.lastname: Wang
mesh_terms: D000251:Adenosine Triphosphatases / Q000235:genetics / Q000378:metabolism*; D020816:Amino Acid Motifs; D045744:Cell Line, Tumor; D003513:Cycloheximide / Q000494:pharmacology; D053843:DNA Mismatch Repair; D045643:DNA Repair Enzymes / Q000235:genetics / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D015536:Down-Regulation; D006367:HeLa Cells; D006801:Humans; D061986:MCF-7 Cells; D000070976:Mismatch Repair Endonuclease PMS2; D010766:Phosphorylation; D011485:Protein Binding / Q000187:drug effects; D051057:Proto-Oncogene Proteins c-akt / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D034622:RNA Interference; D012333:RNA, Messenger / Q000378:metabolism
chemical_list: D004268:DNA-Binding Proteins; D012333:RNA, Messenger; D003513:Cycloheximide; D051057:Proto-Oncogene Proteins c-akt; D000251:Adenosine Triphosphatases; C094934:PMS2 protein, human; D000070976:Mismatch Repair Endonuclease PMS2; D045643:DNA Repair Enzymes