Site-specific ribonuclease activity of eukaryotic DNA topoisomerase I
Site-specific ribonuclease activity of eukaryotic DNA topoisomerase I
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DOI：
10.1016/s1097-2765(00)80010-6
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发表时间：
1997-12-01
期刊：
影响因子：
16
通讯作者：
Shuman, S
中科院分区：
文献类型：
--
作者：
Sekiguchi, J;Shuman, S
I型拓扑异构酶通过切割和重新连接一条双链DNA，通过共价蛋白质-DNA中间体改变DNA拓扑结构。在这里，我们展示了痘苗病毒拓扑异构酶，一种真核型IB酶，催化含有RNA的链的位点特异性内切核裂解。核糖核酸酶反应通过剪切性核苷酸上的酯交换反应形成共价的RNA-3‘-磷酸基酶中间体，然后被核糖的邻位2’-羟基攻击，生成游离的2‘，3’-环状磷酸产物。在另一种全DNA底物的切割磷酸上引入一个核糖核苷，就足以将拓扑异构酶转化为核酸内切酶。人拓扑异构酶I也具有内切核糖核酸酶活性。这些发现提示了拓扑异构酶在RNA加工中的潜在作用。
Type I topoisomerases alter DNA topology by cleaving and rejoining one strand of duplex DNA through a covalent protein-DNA intermediate. Here we show that vaccinia topoisomerase, a eukaryotic type IB enzyme, catalyzes site-specific endoribonucleolytic cleavage of an RNA-containing strand. The RNase reaction occurs via transesterification at the scissile ribonucleotide to form a covalent RNA-3'-phosphoryl-enzyme intermediate, which is then attacked by the vicinal 2' OH of the ribose sugar to yield a free 2', 3' cyclic phosphate product. Introduction of a single ribonucleoside at the scissile phosphate of an otherwise all-DNA substrate suffices to convert the topoisomerase into an endonuclease. Human topoisomerase I also has endoribonuclease activity. These findings suggest potential roles for topoisomerases in RNA processing.