Protein Phosphatase 6 Interacts with the DNA-Dependent Protein Kinase Catalytic Subunit and Dephosphorylates γ-H2AX
Protein Phosphatase 6 Interacts with the DNA-Dependent Protein Kinase Catalytic Subunit and Dephosphorylates γ-H2AX
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DOI：
10.1128/mcb.00741-09
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发表时间：
2010-03-15
影响因子：
5.3
通讯作者：
Lees-Miller, Susan P.
中科院分区：
文献类型：
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作者：
Douglas, Pauline;Zhong, Jianing;Lees-Miller, Susan P.
DNA依赖蛋白激酶催化亚单位(DNA-PKcs)在非同源末端连接(NHEJ)修复DNA双链断裂(DSB)中起重要作用。我们先前已经证明DNA-PKcs在电离辐射(IR)的响应下被自动磷酸化，并且被蛋白磷酸酶2A(PP2A)样蛋白磷酸酶(PP2A、PP4或PP6)去磷酸化调节DNA-PKcs的蛋白激酶活性。在这里，我们报道了DNA-PKcs与PP6(PP6c)和PP2A(PP2Ac)的催化亚基以及PP6调节亚基PP6R1、PP6R2和PP6R3相互作用。与DNA损伤反应中的作用一致，小干扰RNA(SiRNA)沉默PP6c诱导了对IR的敏感性，并延迟了G(2)/M检查点的释放。此外，PP6c或PP6R1的siRNA沉默导致IR后组蛋白H_2AX在丝氨酸139(γ-H_2AX)上的持续磷酸化。相反，沉默PP6c并不影响DNA-PKcs在丝氨酸2056上的自磷酸化，也不影响共济失调毛细血管扩张突变(ATM)蛋白在丝氨酸1981上的自磷酸化。我们认为DNA-PKcs的一个新功能是将PP6募集到DNA损伤部位，PP6在体内有助于伽马-H_2AX的去磷酸化，IR诱导的病灶的溶解，以及从G(2)/M检查点释放。
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.