Protein phosphatase 6 interacts with the DNA-dependent protein kinase catalytic subunit and dephosphorylates gamma-H2AX.

The catalytic subunit of the DNA-dependent protein kinase (DNA-PKcs) plays a major role in the repair of DNA double-strand breaks (DSBs) by nonhomologous end joining (NHEJ). We have previously shown that DNA-PKcs is autophosphorylated in response to ionizing radiation (IR) and that dephosphorylation by a protein phosphatase 2A (PP2A)-like protein ...
phosphatase (PP2A, PP4, or PP6) regulates the protein kinase activity of DNA-PKcs. Here we report that DNA-PKcs interacts with the catalytic subunits of PP6 (PP6c) and PP2A (PP2Ac), as well as with the PP6 regulatory subunits PP6R1, PP6R2, and PP6R3. Consistent with a role in the DNA damage response, silencing of PP6c by small interfering RNA (siRNA) induced sensitivity to IR and delayed release from the G(2)/M checkpoint. Furthermore, siRNA silencing of either PP6c or PP6R1 led to sustained phosphorylation of histone H2AX on serine 139 (gamma-H2AX) after IR. In contrast, silencing of PP6c did not affect the autophosphorylation of DNA-PKcs on serine 2056 or that of the ataxia-telangiectasia mutated (ATM) protein on serine 1981. We propose that a novel function of DNA-PKcs is to recruit PP6 to sites of DNA damage and that PP6 contributes to the dephosphorylation of gamma-H2AX, the dissolution of IR-induced foci, and release from the G(2)/M checkpoint in vivo.
Mesh Terms:
Catalytic Domain, Cell Cycle Proteins, Cell Extracts, Cell Nucleus, Chromosomal Proteins, Non-Histone, Comet Assay, DNA Breaks, Double-Stranded, DNA Repair, DNA-Activated Protein Kinase, DNA-Binding Proteins, G2 Phase, Gene Silencing, Hela Cells, Histones, Humans, Mitosis, Models, Biological, Nuclear Proteins, Phosphoprotein Phosphatases, Phosphorylation, Protein Binding, Protein-Serine-Threonine Kinases, Radiation, Ionizing, Tumor Suppressor Proteins
Mol. Cell. Biol.
Date: Mar. 01, 2010
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