An evolutionarily conserved function of proliferating cell nuclear antigen for Cdt1 degradation by the Cul4-Ddb1 ubiquitin ligase in response to DNA damage
An evolutionarily conserved function of proliferating cell nuclear antigen for Cdt1 degradation by the Cul4-Ddb1 ubiquitin ligase in response to DNA damage
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DOI：
10.1074/jbc.c500464200
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发表时间：
2006-02-17
影响因子：
4.8
通讯作者：
Xiong, Y
中科院分区：
文献类型：
--
作者：
Hu, J;Xiong, Y
在细胞周期的S阶段，DNA复制许可因子CDT1被泛素-蛋白酶体途径降解，以确保在每个细胞分裂过程中进行一轮DNA复制，并对DNA损伤做出反应，以阻止DNA复制。CDT1的结构性表达导致DNA的重新复制，并与人类非小细胞肺癌的亚群的发展有关。在哺乳动物细胞中，DNA损伤诱导的CDT1降解是由CUL4-DDB1-Roc1 E3泛素连接酶催化的。我们在此报道了CDK抑制剂p21和p57的增殖细胞核抗原抑制域的过表达，而不是CDK-细胞周期蛋白抑制域的过表达，阻止了紫外线照射后培养的哺乳动物细胞中CDT1的降解。在体内，可溶性的CDT1和增殖细胞核抗原通过凝胶过滤共洗脱并相互物理结合。沉默培养的哺乳动物细胞中的增殖细胞核抗原或抑制裂解酵母中的pcn1表达可阻止对DNA损伤的CDT1降解。出乎意料的是，在没有DNA损伤的情况下，分裂酵母细胞中DDB1的缺失也积累了CDT1。我们认为，CUL4-DDB1连接酶在正常细胞生长过程中以及在DNA损伤时进化为泛素化CDT1，而另一种单独的E3连接酶，可能是SCFSkp2，在正常细胞生长过程中进化为共享或接管CDT1泛素化的功能，并且增殖细胞核抗原参与介导CUL4-DDB1连接酶对DNA损伤的CDT1降解。
The DNA replication licensing factor Cdt1 is degraded by the ubiquitin-proteasome pathway during S phase of the cell cycle, to ensure one round of DNA replication during each cell division and in response to DNA damage to halt DNA replication. Constitutive expression of Cdt1 causes DNA re-replication and is associated with the development of a subset of human non-small cell-lung carcinomas. In mammalian cells, DNA damage-induced Cdt1 degradation is catalyzed by the Cul4-Ddb1-Roc1 E3 ubiquitin ligase. We report here that overexpression of the proliferating cell nuclear antigen (PCNA) inhibitory domain from the CDK inhibitors p21 and p57, but not the CDK-cyclin inhibitory domain, blocked Cdt1 degradation in cultured mammalian cells after UV irradiation. In vivo soluble Cdt1 and PCNA co-elute by gel filtration and associate with each other physically. Silencing PCNA in cultured mammalian cells or repression of pcn1 expression in fission yeast blocked Cdt1 degradation in response to DNA damage. Unexpectedly, deletion of Ddb1 in fission yeast cells also accumulated Cdt1 in the absence of DNA damage. We suggest that the Cul4-Ddb1 ligase evolved to ubiquitinate Cdt1 during normal cell growth as well as in response to DNA damage and a separate E3 ligase, possibly SCFSkp2, evolved to either share or take over the function of Cdt1 ubiquitination during normal cell growth and that PCNA is involved in mediating Cdt1 degradation by the Cul4-Ddb1 ligase in response to DNA damage.