title: Cyclin G-associated kinase regulates protein phosphatase 2A by phosphorylation of its B'γ subunit.
abstract: Protein phosphatase 2A (PP2A) bearing the B'γ (=B'α/B56γ1/PR61γ) subunit is recruited to dephosphorylation targets by cyclin G. We demonstrate here that cyclin G-associated kinase (GAK), a component of the GAK/B'γ/cyclin G complex, directly phosphorylates the B'γ-Thr104 residue and regulates PP2A activity. Indeed, an anti-B'γ-pT104 antibody detected immunofluorescence signals at the chromosome and centrosome during mitosis; these signals were reduced by siRNA-mediated GAK knockdown. After DNA damage by γ-irradiation, the chromosome signals formed foci that colocalized with a DNA double-strand break (DSB) marker H2AX-pS139 (γH2AX) and CHK2-pT68. Moreover, B'γ-pT104 enhanced PP2A holoenzyme assembly and PP2A activity, as shown by the results of an in vitro phosphatase assay. These results suggest a novel role for GAK as a regulator of dephosphorylation events under the control of the PP2A B'γ subunit.
authors.affiliation: Department of Molecular Genetics, Research Institute for Microbial Diseases, Osaka University, Suita City, Osaka, Japan.
authors.forename: Yoko
authors.initials: Y
authors.lastname: Naito
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Shimizu
authors.forename: Takashi
authors.initials: T
authors.lastname: Kasama
authors.forename: Jun
authors.initials: J
authors.lastname: Sato
authors.forename: Hiroe
authors.initials: H
authors.lastname: Tabara
authors.forename: Ayumi
authors.initials: A
authors.lastname: Okamoto
authors.forename: Norikazu
authors.initials: N
authors.lastname: Yabuta
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Nojima
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D045744:Cell Line, Tumor; D018385:Centrosome / Q000378:metabolism; D064447:Checkpoint Kinase 2; D002875:Chromosomes / Q000378:metabolism; D004249:DNA Damage; D005720:Gamma Rays; D006367:HeLa Cells; D006657:Histones / Q000378:metabolism; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D008938:Mitosis; D008969:Molecular Sequence Data; D010766:Phosphorylation; D054648:Protein Phosphatase 2 / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D021122:Protein Subunits / Q000378:metabolism; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000378:metabolism; D015398:Signal Transduction
chemical_list: C468783:H2AX protein, human; D006657:Histones; D047908:Intracellular Signaling Peptides and Proteins; D021122:Protein Subunits; D034741:RNA, Small Interfering; D064447:Checkpoint Kinase 2; C578634:CHEK2 protein, human; C578633:Chek2 protein, mouse; C486325:GAK protein, human; D017346:Protein Serine-Threonine Kinases; D054648:Protein Phosphatase 2