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.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Amino Acid Sequence
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Animals
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Cell Line, Tumor
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Centrosome / metabolism
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Checkpoint Kinase 2
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Chromosomes / metabolism
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DNA Damage
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Gamma Rays
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HeLa Cells
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Histones / metabolism
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Humans
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Intracellular Signaling Peptides and Proteins / antagonists & inhibitors
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Intracellular Signaling Peptides and Proteins / genetics
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Intracellular Signaling Peptides and Proteins / metabolism*
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Mice
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Mitosis
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Molecular Sequence Data
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Phosphorylation
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Protein Phosphatase 2 / metabolism*
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Protein Serine-Threonine Kinases / antagonists & inhibitors
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Protein Serine-Threonine Kinases / genetics
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Protein Serine-Threonine Kinases / metabolism*
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Protein Subunits / metabolism
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RNA Interference
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RNA, Small Interfering / metabolism
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Signal Transduction
Substances
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H2AX protein, human
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Histones
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Intracellular Signaling Peptides and Proteins
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Protein Subunits
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RNA, Small Interfering
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Checkpoint Kinase 2
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CHEK2 protein, human
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Chek2 protein, mouse
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GAK protein, human
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Protein Serine-Threonine Kinases
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Protein Phosphatase 2