Regulation of ubiquitination and degradation of p53 in unstressed cells through C-terminal phosphorylation
Regulation of ubiquitination and degradation of p53 in unstressed cells through C-terminal phosphorylation
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DOI：
10.1074/jbc.m103170200
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发表时间：
2001-08-24
影响因子：
4.8
通讯作者：
Stark, GR
中科院分区：
文献类型：
--
作者：
Chernov, MV;Bean, LJH;Stark, GR
以前，我们发现蛋白激酶C（PKC）抑制剂H7刺激p53以不能诱导p53依赖性启动子转录的形式积累。我们的结论是，H7抑制组成性的C-末端磷酸化的p53，调节其营业额在非应激细胞。我们现在表明，p53和它的抑制剂MDM 2（人类细胞中的HDM 2）一起在H7处理的细胞的细胞核中，可以共免疫沉淀。尽管p53与泛素连接酶MDM 2有这种关联，但在H7处理的细胞中未检测到泛素化的p53。此外，H7和蛋白体抑制剂LLnL的共同处理可以防止遍在蛋白化p53的积累，这在仅用LLnL处理的细胞中观察到。此外，用PKC激活剂佛波酯处理细胞刺激了p53的泛素化，并降低了其在应激后积累的能力。H7不诱导人p53在Ser-15（小鼠蛋白中的Ser-18）上的磷酸化，这是响应DNA损伤而发生的修饰，并导致MDM 2的释放和p53的反式激活。我们的结论是，磷酸化的C-末端结构域的p53蛋白激酶C增加其在非应激细胞中的泛素化和降解。
Previously, we found that the protein kinase C (PKC) inhibitor H7 stimulates p53 to accumulate in a form incapable of inducing transcription from p53-dependent promoters. We concluded that H7 inhibits constitutive C-terminal phosphorylation of p53, which regulates its turnover in unstressed cells. We now show that p53 and its inhibitor MDM2 (HDM2 in human cells) are together in the nuclei of H7-treated cells and can be co-immunoprecipitated. Despite this association of p53 with the ubiquitin ligase MDM2, ubiquitinated p53 was not detected in H7-treated cells. Furthermore, co-treatment with H7 and the proteosome inhibitor LLnL prevented the accumulation of ubiquitinated p53 that was observed in cells treated solely with LLnL. In addition, treatment of cells with the PKC activator phorbol ester stimulated the ubiquitination of p53 and reduced its ability to accumulate after stress. H7 did not induce the phosphorylation of human p53 on Ser-15 (Ser-18 in mouse protein), a modification that occurs in response to DNA damage and leads to the release of MDM2 and to transactivation by p53. We conclude that phosphorylation of the C-terminal domain of p53 by PKC increases its ubiquitination and degradation in unstressed cells.