Structural analysis of human Orc6 protein reveals a homology with transcription factor TFIIB
Structural analysis of human Orc6 protein reveals a homology with transcription factor TFIIB
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人类 Orc6 蛋白的结构分析揭示与转录因子 TFIIB 的同源性
DOI：
10.1073/pnas.1013676108
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发表时间：
2011-05-03
影响因子：
11.1
通讯作者：
Liu, Yingfang
中科院分区：
文献类型：
--
作者：
Liu, Shixuan;Balasov, Maxim;Liu, Yingfang
起源识别复合物（ORC）是一种六亚基蛋白，对真核细胞中DNA复制的起始非常重要。Orc6是ORC亚基中最小和最不保守的亚基。Orc6是DNA复制所必需的，但在后生动物物种的胞质分裂中也具有功能，然而，Orc6在这些过程中的作用机制尚不清楚。在这里，我们报告了人类Orc6的中间结构域的结构。该结构域具有与转录因子TFIIB的相应螺旋结构域相似的总体折叠。基于这些发现，产生了Orc6与DNA结合的模型。我们已经鉴定了直接参与DNA结合的Orc6的氨基酸。这些氨基酸的改变消除了Orc6的DNA结合能力，并且还导致体外和培养细胞中DNA复制水平降低。我们的数据表明，Orc6是后生动物物种的ORC的DNA结合亚基之一。我们建议，Orc6可能参与定位的ORC在DNA复制的起点类似的作用TFIIB定位转录前起始复合物的启动子。
The Origin Recognition Complex (ORC) is a six-subunit protein important for the initiation of DNA replication in eukaryotic cells. Orc6 is the smallest and the least conserved among ORC subunits. It is required for the DNA replication but also has a function in cytokinesis in metazoan species, however, the mechanisms of Orc6 action in these processes are not clear. Here we report a structure of the middle domain of human Orc6. This domain has an overall fold similar to the corresponding helical domain of transcription factor TFIIB. Based on these findings, a model of Orc6 binding to DNA is produced. We have identified amino acids of Orc6 which are directly involved in DNA binding. Alterations of these amino acids abolish DNA binding ability of Orc6 and also result in reduced levels of DNA replication in vitro and in cultured cells. Our data indicate that Orc6 is one of the DNA binding subunits of ORC in metazoan species. We propose that Orc6 may participate in positioning of ORC at the origins of DNA replication similar to the role of TFIIB in positioning transcription preinitiation complex at the promoter.