Nature：破解17年细胞分裂难题

　　

生物通报道，来自英国伦敦研究所癌症研究中心，蛋白分析和蛋白组学实验室，遗传重组研究实验室，Clare Hall实验室的科学家的科学家破解17年的难题，找到哺乳动物的Holliday junction 解离酶。相关成果文章发表在最新一期11月20日的Nature上。

 

细胞分裂过程中，其中的一个步骤是将拷贝的DNA重新分配成为两份均等的DNA，在这一过程中，两个DNA分子以公价键方式连接在一起，形成一个名为Holliday junction（霍利迪连接体）。进入下一步时，需要有一种解离酶来分开两个相连的DNA分子。

 

早在上个世纪90年代，科学家在大肠杆菌中发现了解离酶，由ruvC基因编码表达。科学家猜想，在真核细胞中，尤其是在哺乳动物的细胞中应该也存在类似的酶。这一找，就花去了17年时间，现在来自英国的科学家终于在哺乳动物细胞中发现这类酶。

 

研究者通过两种不同的方法找出人类的解离酶GEN 1和酵母细胞的解离酶Yen1。GEN 1是从海拉癌细胞株的无细胞提取液中通过大量的光谱测定扫描找出的。而Yen 1是从酵母的基因融合文库中找到的。GEN 1和Yen 1是同源直系蛋白，二者都是结构特异性核酶的Rad2/XPG 家族的成员，是Rad/XPG家族里的一类新的亚类。

 

原文摘要：Identification of Holliday junction resolvases from humans and yeast

 

【Abstract】

Four-way DNA intermediates, also known as Holliday junctions, are formed during homologous recombination and DNA repair, and their resolution is necessary for proper chromosome segregation. Here we identify nucleases from Saccharomyces cerevisiae and human cells that promote Holliday junction resolution, in a manner analogous to that shown by the Escherichia coli Holliday junction resolvase RuvC. The human Holliday junction resolvase, GEN1, and its yeast orthologue, Yen1, were independently identified using two distinct experimental approaches: GEN1 was identified by mass spectrometry following extensive fractionation of HeLa cell-free extracts, whereas Yen1 was detected by screening a yeast gene fusion library for nucleases capable of Holliday junction resolution. The eukaryotic Holliday junction resolvases represent a new subclass of the Rad2/XPG family of nucleases. Recombinant GEN1 and Yen1 resolve Holliday junctions by the introduction of symmetrically related cuts across the junction point, to produce nicked duplex products in which the nicks can be readily ligated.

生物通 张欢