Epidermal Growth Factor Receptor Protects Proliferating Cell Nuclear Antigen from Cullin 4A Protein-mediated Proteolysis
Epidermal Growth Factor Receptor Protects Proliferating Cell Nuclear Antigen from Cullin 4A Protein-mediated Proteolysis
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DOI：
10.1074/jbc.m112.388843
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发表时间：
2012-08-03
影响因子：
4.8
通讯作者：
Wang, Shao-Chun
中科院分区：
文献类型：
--
作者：
Lo, Yuan-Hung;Ho, Po-Chun;Wang, Shao-Chun
增殖细胞核抗原（PCNA）是生长刺激下DNA合成的重要组成部分。研究表明，EGF受体（EGFR）对PCNA tyr1 -211位点的磷酸化可保护PCNA免受多泛素化和降解的影响，而阻断磷酸化可诱导泛素化介导的染色质结合而非非结合PCNA的降解，并抑制细胞增殖。然而，连接生长信号与PCNA蛋白水解的泛素E3连接酶及其潜在的调控机制仍有待确定。本研究表明，在没有tyr1 -211磷酸化的情况下，PCNA在Lys-164位点被CUL4A E3连接酶多泛素化，导致PCNA降解。Lys-164向精氨酸的突变阻止了PCNA泛素化，挽救了K164R/Y211F PCNA双突变体的降解。激活EGFR可抑制PCNA与CUL4A的相互作用，而抑制EGFR可增加CUL4A-PCNA相互作用和CUL4A依赖的泛素介导的PCNA降解。用Y211F突变体PCNA替代内源性PCNA可增强对EGFR抑制的敏感性。我们的研究发现CUL4A是癌细胞中连接细胞表面受体酪氨酸激酶下调与细胞核DNA复制机制的泛素连接酶。
Proliferating cell nuclear antigen (PCNA) is an essential component for DNA synthesis upon growth stimulation. It has been shown that phosphorylation of PCNA at Tyr-211 by the EGF receptor (EGFR) protects PCNA from polyubiquitylation and degradation, whereas blocking phosphorylation induces ubiquitylation-mediated degradation of the chromatin-bound, but not the -unbound, PCNA, and suppresses cell proliferation. However, the ubiquitin E3 ligase linking growth signaling to the proteolysis of PCNA and the underlying regulatory mechanism remain to be identified. Here we show that, in the absence of Tyr-211 phosphorylation, PCNA is subject to polyubiquitylation at Lys-164 by the CUL4A E3 ligase, resulting in the degradation of PCNA. Mutation of Lys-164 to arginine prevents PCNA ubiquitylation and rescues the degradation of the K164R/Y211F PCNA double mutant. Activation of EGFR inhibits the interaction of PCNA with CUL4A, whereas inhibition of EGFR leads to increased CUL4A-PCNA interaction and CUL4A-dependent ubiquitin-mediated degradation of PCNA. Substitution of endogenous PCNA with the Y211F mutant PCNA conveys enhanced sensitization to EGFR inhibition. Our findings identify CUL4A as the ubiquitin ligase linking the down-regulation of cell surface receptor tyrosine kinase to the nuclear DNA replication machinery in cancer cells.