Burgess B R, Richardson J P
Department of Chemistry, Indiana University, Bloomington, Indiana 47405, USA.
J Biol Chem. 2001 May 18;276(20):17106-10. doi: 10.1074/jbc.M101856200. Epub 2001 Mar 6.
Escherichia coli Rho factor is a ring-shaped, homohexameric protein that terminates synthesis of RNA through interactions with the nascent RNA transcript. Because its mechanism of action may involve translocation of the RNA transcript through the hole in its ring structure, its action could depend on the availability of a free 5' terminus. To determine whether Rho's activity is 5'-end-dependent, its ability to bind to and function on a circular derivative of lambda cro mRNA was investigated. The circular derivative was made in vitro by action of RNA ligase on a derivative of lambda cro RNA containing an extra 10-nucleotide sequence near the 5'-end that was complementary to a sequence located near the 3'-end. Rho bound nearly as tightly to the circular derivative RNA as to the standard cro transcript. Rho was also able to readily dissociate a DNA oligonucleotide from its helical complex with the circular RNA in an ATP-dependent reaction. Thus, the action of Rho on a transcript does not depend on the availability of a free 5' terminus.
大肠杆菌Rho因子是一种环状的同六聚体蛋白，它通过与新生的RNA转录本相互作用来终止RNA的合成。由于其作用机制可能涉及RNA转录本通过其环状结构中的孔进行易位，其作用可能取决于游离5'末端的可用性。为了确定Rho的活性是否依赖于5'末端，研究了它与λ cro mRNA环状衍生物结合并发挥作用的能力。该环状衍生物是通过RNA连接酶作用于λ cro RNA的衍生物在体外制备的，该衍生物在5'末端附近含有一个额外的10个核苷酸序列，与3'末端附近的一个序列互补。Rho与环状衍生物RNA的结合紧密程度几乎与标准cro转录本相同。在ATP依赖的反应中，Rho还能够轻易地将DNA寡核苷酸从其与环状RNA的螺旋复合物中解离出来。因此，Rho对转录本的作用不依赖于游离5'末端的可用性。
