title: Protein serine/threonine phosphatase-1 dephosphorylates p53 at Ser-15 and Ser-37 to modulate its transcriptional and apoptotic activities.
abstract: We have previously demonstrated that the serine/threonine protein phosphatase-1 (PP-1) plays an important role in promoting cell survival. However, the molecular mechanisms by which PP-1 promotes survival remain largely unknown. In the present study, we provide evidence to show that PP-1 can directly dephosphorylate a master regulator of apoptosis, p53, to negatively modulate its transcriptional and apoptotic activities, and thus to promote cell survival. As a transcriptional factor, the function of p53 can be greatly regulated by phosphorylation and dephosphorylation. While the kinases responsible for phosphorylation of the 17 serine/threonine sites have been identified, the dephosphorylation of these sites remains largely unknown. In the present study, we demonstrate that PP-1 can dephosphorylate p53 at Ser-15 and Ser-37 through co-immunoprecipitation, in vitro and in vivo dephosphorylation assays, overexpression and silence of the gene encoding the catalytic subunit for PP-1. We further show that mutations mimicking constitutive dephosphorylation or phosphorylation of p53 at these sites attenuate or enhance its transcriptional activity, respectively. As a result of the changed p53 activity, expression of the downstream apoptosis-related genes such as bcl-2 and bax is accordingly altered and the apoptotic events are either largely abrogated or enhanced. Thus, our results demonstrate that PP-1 directly dephosphorylates p53, and dephosphorylation of p53 has as important impact on its functions as phosphorylation does. In addition, our results reveal that one of the molecular mechanisms by which PP-1 promotes cell survival is to dephosphorylate p53, and thus negatively regulate p53-dependent death pathway.
authors.affiliation: The Hormel Institute, University of Minnesota, Austin, 55912, USA. dwli1688@hotmail.com
authors.forename: D W-C
authors.initials: DW
authors.lastname: Li
authors.forename: J-P
authors.initials: JP
authors.lastname: Liu
authors.forename: P C
authors.initials: PC
authors.lastname: Schmid
authors.forename: R
authors.initials: R
authors.lastname: Schlosser
authors.forename: H
authors.initials: H
authors.lastname: Feng
authors.forename: W-B
authors.initials: WB
authors.lastname: Liu
authors.forename: Q
authors.initials: Q
authors.lastname: Yan
authors.forename: L
authors.initials: L
authors.lastname: Gong
authors.forename: S-M
authors.initials: SM
authors.lastname: Sun
authors.forename: M
authors.initials: M
authors.lastname: Deng
authors.forename: Y
authors.initials: Y
authors.lastname: Liu
mesh_terms: D019943:Amino Acid Substitution; D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D002460:Cell Line / Q000187:drug effects / Q000201:enzymology; D004847:Epithelial Cells / Q000187:drug effects / Q000378:metabolism; D017930:Genes, Reporter; D019254:Genes, bcl-2; D016158:Genes, p53; D006801:Humans; D047468:Immunoprecipitation; D007908:Lens, Crystalline / Q000166:cytology; D008387:Marine Toxins; D051379:Mice; D018345:Mice, Knockout; D019319:Okadaic Acid / Q000494:pharmacology; D010080:Oxazoles / Q000494:pharmacology; D010749:Phosphoprotein Phosphatases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000502:physiology*; D010766:Phosphorylation / Q000187:drug effects; D010768:Phosphoserine / Q000378:metabolism*; D011485:Protein Binding; D025941:Protein Interaction Mapping; D054645:Protein Phosphatase 1; D011499:Protein Processing, Post-Translational / Q000187:drug effects / Q000502:physiology*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000096:biosynthesis; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000494:pharmacology; D011993:Recombinant Fusion Proteins / Q000502:physiology; D014158:Transcription, Genetic / Q000187:drug effects / Q000502:physiology*; D016159:Tumor Suppressor Protein p53 / Q000737:chemistry / Q000378:metabolism*; D051028:bcl-2-Associated X Protein / Q000096:biosynthesis / Q000235:genetics
chemical_list: D008387:Marine Toxins; D010080:Oxazoles; D019253:Proto-Oncogene Proteins c-bcl-2; D034741:RNA, Small Interfering; D011993:Recombinant Fusion Proteins; D016159:Tumor Suppressor Protein p53; D051028:bcl-2-Associated X Protein; D010768:Phosphoserine; D019319:Okadaic Acid; C059041:calyculin A; D010749:Phosphoprotein Phosphatases; D054645:Protein Phosphatase 1