Ottawa Health Research Institute, Ottawa, Ontario, Canada.
Oncogene. 2010 Apr 8;29(14):2093-103. doi: 10.1038/onc.2009.492. Epub 2010 Jan 25.
Poly (ADP-ribose) polymerase-1 (PARP-1) has an important role in the cellular response to a broad spectrum of DNA lesions. PARP-1 is strongly activated in response to double-stranded DNA breaks (DSBs), yet its contribution to the DSB response is poorly understood. Here we used bleomycin, a radiomimetic that generates DSBs with high specificity to focus on the response of PARP-1 to DSBs. We report that the induction of PARP-1 activity by bleomycin depends on the Ku antigen, a nonhomologous-DNA-End-Joining factor and protein phosphatase 5 (PP5). PARP-1 activation in response to bleomycin was reduced over 10-fold in Ku-deficient cells, whereas its activation in response to U.V. was unaffected. PARP-1 activation was rescued by reexpression of Ku, but was refractory to manipulation of DNA-dependent protein kinase or ATM. Similarly, PARP-1 activation subsequent to bleomycin was reduced 2-fold on ablation of PP5 and was increased 5-fold when PP5 was overexpressed. PP5 seemed to act directly on PARP-1, as its basal phosphorylation was reduced on overexpression of PP5, and PP5 dephosphorylated PARP-1 in vitro. These results highlight the functional importance of Ku antigen and PP5 for PARP-1 activity subsequent to DSBs.
聚（ADP-核糖）聚合酶-1（PARP-1）在细胞对广泛的 DNA 损伤的反应中具有重要作用。PARP-1 对双链 DNA 断裂（DSBs）的反应强烈激活，但对 DSB 反应的贡献尚不清楚。在这里，我们使用博来霉素，一种具有高度特异性产生 DSB 的放射模拟物，专注于 PARP-1 对 DSB 的反应。我们报告说，博来霉素诱导 PARP-1 活性依赖于 Ku 抗原，一种非同源 DNA 末端连接因子和蛋白磷酸酶 5（PP5）。Ku 缺陷细胞中 PARP-1 活性的诱导降低了 10 倍以上，而对 U.V. 的激活不受影响。Ku 的重新表达挽救了 PARP-1 的激活，但对 DNA 依赖性蛋白激酶或 ATM 的操作无反应。同样，博来霉素处理后 PARP-1 的激活在 PP5 缺失时降低了 2 倍，而在 PP5 过表达时增加了 5 倍。PP5 似乎直接作用于 PARP-1，因为其基础磷酸化在 PP5 的过表达时降低，并且 PP5 在体外去磷酸化 PARP-1。这些结果突出了 Ku 抗原和 PP5 对 DSB 后 PARP-1 活性的功能重要性。
