Liu Bin, Steitz Thomas A
Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06520, USA.
Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06520, USA
Nucleic Acids Res. 2017 Jan 25;45(2):968-974. doi: 10.1093/nar/gkw1159. Epub 2016 Nov 29.
NusG is an essential transcription factor that plays multiple key regulatory roles in transcription elongation, termination and coupling translation and transcription. The core role of NusG is to enhance transcription elongation and RNA polymerase processivity. Here, we present the structure of Escherichia coli RNA polymerase complexed with NusG. The structure shows that the NusG N-terminal domain (NGN) binds at the central cleft of RNA polymerase surrounded by the β' clamp helices, the β protrusion, and the β lobe domains to close the promoter DNA binding channel and constrain the β' clamp domain, but with an orientation that is different from the one observed in the archaeal β' clamp-Spt4/5 complex. The structure also allows us to construct a reliable model of the complete NusG-associated transcription elongation complex, suggesting that the NGN domain binds at the upstream fork junction of the transcription elongation complex, similar to σ2 in the transcription initiation complex, to stabilize the junction, and therefore enhances transcription processivity.
NusG是一种必需的转录因子，在转录延伸、终止以及转录与翻译的偶联过程中发挥多种关键调控作用。NusG的核心作用是增强转录延伸和RNA聚合酶的持续合成能力。在此，我们展示了与NusG复合的大肠杆菌RNA聚合酶的结构。该结构表明，NusG的N端结构域（NGN）结合在RNA聚合酶的中央裂隙处，周围环绕着β'钳螺旋、β突出部和β叶结构域，以关闭启动子DNA结合通道并限制β'钳结构域，但其取向与古细菌β'钳-Spt4/5复合物中观察到的不同。该结构还使我们能够构建一个完整的与NusG相关的转录延伸复合物的可靠模型，表明NGN结构域结合在转录延伸复合物的上游叉状连接处，类似于转录起始复合物中的σ2，以稳定该连接处，从而增强转录持续合成能力。
