Altmann C R, Solow-Cordero D E, Chamberlin M J
Department of Molecular and Cell Biology, University of California, Berkeley 94720.
Proc Natl Acad Sci U S A. 1994 Apr 26;91(9):3784-8. doi: 10.1073/pnas.91.9.3784.
In the absence of DNA, Escherichia coli RNA polymerase (EC 2.7.7.6) can bind RNA to form an equimolar binary complex with the concomitant release of the sigma factor. We show now that E. coli RNA polymerase binds at a region near the 3' terminus of the RNA and that an RNA in such RNA.RNA polymerase complexes undergoes reactions previously thought to be unique to nascent RNA in ternary complexes with DNA. These include GreA/GreB-dependent cleavage of the RNA and elongation by 3'-terminal addition of NMP from NTP. Both of these reactions are inhibited by rifampicin. Hence, by several criteria, the RNA in binary complexes is bound to the polymerase in a manner quite similar to that in ternary complexes. These findings can be explained by a model for the RNA polymerase ternary complex in which the RNA is bound at the 3' terminus through two protein binding sites located up to 10 nt apart. In this model, the stability of RNA binding to the polymerase in the ternary complex is due primarily to its interaction with the protein.
在没有DNA的情况下，大肠杆菌RNA聚合酶（EC 2.7.7.6）可与RNA结合形成等摩尔二元复合物，并伴随σ因子的释放。我们现在表明，大肠杆菌RNA聚合酶结合在RNA 3'末端附近的区域，并且这种RNA·RNA聚合酶复合物中的RNA会发生以前认为仅在与DNA形成的三元复合物中的新生RNA才具有的反应。这些反应包括GreA/GreB依赖的RNA切割以及通过从NTP进行3'末端添加NMP来实现延伸。这两种反应均受利福平抑制。因此，从几个标准来看，二元复合物中的RNA与聚合酶的结合方式与三元复合物中的非常相似。这些发现可以通过RNA聚合酶三元复合物的模型来解释，在该模型中，RNA通过两个相距达10个核苷酸的蛋白质结合位点在3'末端结合。在这个模型中，三元复合物中RNA与聚合酶结合的稳定性主要归因于其与蛋白质的相互作用。
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