Key Laboratory of Synthetic Biology, CAS Center for Excellence in Molecular Plant Sciences, Shanghai Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, 200032, Shanghai, China.
University of Chinese Academy of Sciences, 100049, Beijing, China.
Nat Commun. 2019 Jul 11;10(1):3048. doi: 10.1038/s41467-019-10955-x.
Bacteriophages typically hijack the host bacterial transcriptional machinery to regulate their own gene expression and that of the host bacteria. The structural basis for bacteriophage protein-mediated transcription regulation-in particular transcription antitermination-is largely unknown. Here we report the 3.4 Å and 4.0 Å cryo-EM structures of two bacterial transcription elongation complexes (P7-NusA-TEC and P7-TEC) comprising the bacteriophage protein P7, a master host-transcription regulator encoded by bacteriophage Xp10 of the rice pathogen Xanthomonas oryzae pv. Oryzae (Xoo) and discuss the mechanisms by which P7 modulates the host bacterial RNAP. The structures together with biochemical evidence demonstrate that P7 prevents transcription termination by plugging up the RNAP RNA-exit channel and impeding RNA-hairpin formation at the intrinsic terminator. Moreover, P7 inhibits transcription initiation by restraining RNAP-clamp motions. Our study reveals the structural basis for transcription antitermination by phage proteins and provides insights into bacterial transcription regulation.
噬菌体通常会劫持宿主细菌的转录机制来调控自身基因表达和宿主细菌的基因表达。噬菌体蛋白介导的转录调控的结构基础，特别是转录终止抑制，在很大程度上是未知的。在这里，我们报道了两个细菌转录延伸复合物（P7-NusA-TEC 和 P7-TEC）的 3.4Å 和 4.0Å 冷冻电镜结构，这两个复合物包含噬菌体蛋白 P7，它是由水稻病原菌稻黄单胞菌 pv. 编码的噬菌体 Xp10 编码的主要宿主转录调控因子（Xoo），并讨论了 P7 调节宿主细菌 RNA 聚合酶的机制。这些结构以及生化证据表明，P7 通过堵塞 RNA 聚合酶 RNA 出口通道并阻碍内在终止子处的 RNA 发夹形成来阻止转录终止。此外，P7 通过限制 RNA 聚合酶夹钳运动来抑制转录起始。我们的研究揭示了噬菌体蛋白转录终止抑制的结构基础，并为细菌转录调控提供了新的见解。
