BRCA1/BARD1 ubiquitinate phosphorylated RNA polymerase II
BRCA1/BARD1 ubiquitinate phosphorylated RNA polymerase II
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DOI：
10.1074/jbc.m414020200
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发表时间：
2005-07-01
影响因子：
4.8
通讯作者：
Chiba, N
中科院分区：
文献类型：
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作者：
Starita, LM;Horwitz, AA;Chiba, N
乳腺和卵巢特异性肿瘤抑制因子BRCA 1与BARD 1结合时，是一种泛素连接酶。我们在这里已经表明，这种异源二聚体泛素化的超磷酸化形式的Rpb 1，RNA聚合酶II的最大亚基。两个主要的磷酸化位点已被确定在Rpb 1的羧基末端结构域，丝氨酸2（Ser-2）或丝氨酸5（Ser-5）的YSPTSPS七肽重复。只有Ser-5过度磷酸化的形式被BRCA 1/BARD 1泛素化。BRCA 1在细胞中的过表达刺激了DNA损伤诱导的Rpb 1泛素化。与体外反应相似，BRCA 1刺激细胞中Rpb 1泛素化仅发生在七肽重复的Ser-5上过度磷酸化的那些分子上。在体外，BRCA 1的羧基末端（氨基酸501-1863）被过度磷酸化的Rpb 1的泛素化所取代。然而，在细胞中，有效的Rpb 1泛素化需要BRCA 1的羧基末端，这表明该区域介导的相互作用在复杂的细胞核环境中是必不可少的。这些结果将BRCA 1依赖的聚合酶泛素化与DNA损伤联系起来。
The breast- and ovarian-specific tumor suppressor BRCA1, when associated with BARD1, is an ubiquitin ligase. We have shown here that this heterodimer ubiquitinates a hyperphosphorylated form of Rpb1, the largest subunit of RNA polymerase II. Two major phosphorylation sites have been identified in the Rpb1 carboxyl terminal domain, serine 2 ( Ser-2) or serine 5 ( Ser-5) of the YSPTSPS heptapeptide repeat. Only the Ser-5 hyperphosphorylated form is ubiquitinated by BRCA1/BARD1. Overexpression of BRCA1 in cells stimulated the DNA damage-induced ubiquitination of Rpb1. Similar to the in vitro reaction, the stimulation of Rpb1 ubiquitination by BRCA1 in cells occurred only on those molecules hyperphosphorylated on Ser-5 of the heptapeptide repeat. In vitro, the carboxyl terminus of BRCA1 ( amino acids 501-1863) was dispensable for the ubiquitination of hyperphosphorylated Rpb1. In cells, however, efficient Rpb1 ubiquitination required the carboxyl terminus of BRCA1, suggesting that interactions mediated by this region were essential in the complex milieu of the nucleus. These results link the BRCA1-dependent ubiquitination of the polymerase with DNA damage.