Nucleophosmin/B23 is a candidate substrate for the BRCA1-BARD1 ubiquitin ligase
Nucleophosmin/B23 is a candidate substrate for the BRCA1-BARD1 ubiquitin ligase
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DOI：
10.1074/jbc.c400169200
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发表时间：
2004-07-23
影响因子：
4.8
通讯作者：
Ohta, T
中科院分区：
文献类型：
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作者：
Sato, K;Hayami, R;Ohta, T
乳腺和卵巢肿瘤抑制因子BRCA1与BARD1形成异二聚环型泛素连接酶，催化非传统的Lys-6连接的多泛素链。目前还不清楚BRCA1-BARD1连接酶如何调控各种细胞过程，如DNA修复、细胞周期进展、转录调控和中心体复制。在这里，我们报道了BRCA1-BARD1催化核仁磷蛋白Noposmin/B23(NPM)的多泛素化。BRCA1-BARD1泛素化蛋白质的两个不同的质谱屏都识别了NPM。NPM与BRCA1和BARD1的N-末端片段以依赖于BRCA1-BARD1异二聚体形成的方式相互作用。在有丝分裂细胞中，NPM与BRCA1和BARD1共存，提示BRCA1-BARD1可能在有丝分裂过程中对NPM进行调控。BRCA1-BARD1在体外和体内催化NPM的泛素化，BRCA1-BARD1在细胞中的共表达导致NPM稳定而不是降解。这与这种连接酶催化非传统的多泛素链的观点是一致的。鉴于NPM和BRCA1之间有许多重叠的功能，我们认为NPM是BRCA1-BARD1泛素连接酶底物的有力候选者。
The breast and ovarian tumor suppressor BRCA1 forms a heterodimeric RING-type ubiquitin ligase with BARD1 to catalyze untraditional Lys-6-linked polyubiquitin chains. It is not clear how the BRCA1-BARD1 ligase regulates various cellular processes such as DNA repair, cell-cycle progression, transcriptional regulation, and centrosome duplication. Here we report that BRCA1-BARD1 catalyzes the polyubiquitination of nucleolar phosphoprotein nucleophosmin/B23 (NPM). Two different mass spectrometry screens for protein ubiquitinated by BRCA1-BARD1 both identified NPM. NPM interacts with N-terminal fragments of BRCA1 and BARD1 in a manner dependent upon BRCA1-BARD1 heterodimer formation. NPM colocalizes with BRCA1 and BARD1 in mitotic cells suggesting the possibility of NPM regulation by BRCA1-BARD1 during mitosis. BRCA1-BARD1 catalyzes the ubiquitination of NPM in vitro and in vivo, and BRCA1-BARD1 co-expression in cells causes NPM stabilization rather than degradation. This is consistent with the notion that this ligase catalyzes untraditional polyubiquitin chains. Given the many overlapped functions between NPM and BRCA1, we propose that NPM is a strong candidate as a substrate of the BRCA1-BARD1 ubiquitin ligase.