PML contributes to p53-independent p21 up-regulation in gamma-irradiation induced DNA damage responses
PML contributes to p53-independent p21 up-regulation in gamma-irradiation induced DNA damage responses
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DOI：
10.1007/s11434-011-4566-0
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发表时间：
2011-10
影响因子：
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通讯作者：
Lin-Lin Cao-Lin;Yi Song;Bao-lei Tian;Ji-Long Liu;B. Liu;Jianing Zhang;Zhi-xian Sun
中科院分区：
文献类型：
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作者：
Lin-Lin Cao-Lin;Yi Song;Bao-lei Tian;Ji-Long Liu;B. Liu;Jianing Zhang;Zhi-xian Sun
细胞周期蛋白依赖性激酶抑制剂 p21WAF1/Cip1 是一种关键的细胞周期调节因子，在 DNA 损伤反应期间，它易位到细胞核中参与 DNA 修复。在本研究中，我们发现肿瘤抑制因子早幼粒细胞白血病蛋白 (PML) 有助于在不依赖于 p53 的途径中上调 p21。通过特异性 siRNA 敲低 p53 缺失的 H1299 和 HCT 116 (p53−/−) 肿瘤细胞中的 PML，导致 p21 蛋白表达下调，抑制 γ 辐射诱导的 p21 上调，并缩短 p21 蛋白半衰期。在 PML 敲低的 H1299 细胞中，p21 蛋白表达的下调被 MG132 处理逆转，表明 p21 蛋白的蛋白酶体降解增加。因此，PML 通过抑制蛋白酶体介导的蛋白水解作用来正向调节 p21 的表达。 PML 的敲除减少了 γ 辐射诱导的双链断裂 (DSB) 的修复，如 γ-H2AX 焦点的延迟消失以及 p21 和增殖细胞核抗原 (PCNA) 之间的关联减少所表明的。 p21的过度表达显着恢复了延迟的DSB修复功能。总而言之，这些数据为 γ 辐射诱导的 DNA 损伤反应中 PML 和 p21 之间存在独立于 p53 的功能关系提供了证据，并确定 PML 是 p53 缺陷肿瘤细胞中 p21 的正翻译后调节因子。
The cyclin-dependent kinase inhibitor p21WAF1/Cip1is a critical cell cycle regulator which translocates into the nucleus to participate in DNA repair during DNA damage responses. In the present study, we showed that the tumor suppressor, promyelocytic leukemia protein (PML) contributes to the up-regulation of p21 in a p53-independent pathway. Knock-down of PML in p53-null H1299 and HCT 116 (p53−/−) tumor cells by specific siRNA resulted in down-regulation of p21 protein expression, inhibition of γ-irradiation-induced p21 up-regulation, and a decrease in p21 protein half-life. In PML knockdown H1299 cells, the down-regulation of p21 protein expression was reversed by MG132 treatment indicating that the proteasomal degradation of p21 protein was increased. Thus, PML positively regulates p21 expression by inhibiting proteasome-mediated proteolysis. Knockdown of PML decreased the repair of γ-irradiation-induced double strand breaks (DSBs) as indicated by the delayed disappearance of γ-H2AX foci and a decreased association between p21 and proliferating cell nuclear antigen (PCNA). Over-expression of p21 significantly restored the delayed DSB repair function. Taken together, these data provide evidence for a p53-independent functional relationship between PML and p21 in γ-irradiation-induced DNA damage responses, and identify PML as a positive post-translational regulator of p21 in p53-deficient tumor cells.