Key Laboratory of Synthetic Biology, National Key Laboratory of Plant Design, CAS Center for Excellence in Molecular Plant Sciences, Shanghai Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, Shanghai, China.
University of Chinese Academy of Sciences, Beijing, China.
Nature. 2024 Apr;628(8009):887-893. doi: 10.1038/s41586-024-07240-3. Epub 2024 Mar 27.
Efficient termination is required for robust gene transcription. Eukaryotic organisms use a conserved exoribonuclease-mediated mechanism to terminate the mRNA transcription by RNA polymerase II (Pol II). Here we report two cryogenic electron microscopy structures of Saccharomyces cerevisiae Pol II pre-termination transcription complexes bound to the 5'-to-3' exoribonuclease Rat1 and its partner Rai1. Our structures show that Rat1 displaces the elongation factor Spt5 to dock at the Pol II stalk domain. Rat1 shields the RNA exit channel of Pol II, guides the nascent RNA towards its active centre and stacks three nucleotides at the 5' terminus of the nascent RNA. The structures further show that Rat1 rotates towards Pol II as it shortens RNA. Our results provide the structural mechanism for the Rat1-mediated termination of mRNA transcription by Pol II in yeast and the exoribonuclease-mediated termination of mRNA transcription in other eukaryotes.
有效的终止对于稳健的基因转录是必需的。真核生物利用一种保守的核外核酸酶介导的机制，通过 RNA 聚合酶 II（Pol II）终止 mRNA 转录。在这里，我们报告了酿酒酵母 Pol II 预终止转录复合物与 5'-到-3' 外切核酸酶 Rat1 及其伴侣 Rai1 结合的两个低温电子显微镜结构。我们的结构表明，Rat1 取代延伸因子 Spt5 以停靠在 Pol II 柄结构域上。Rat1 遮蔽了 Pol II 的 RNA 出口通道，引导新生 RNA 向其活性中心移动，并在新生 RNA 的 5' 末端堆积三个核苷酸。这些结构进一步表明，随着 Rat1 缩短 RNA，它会向 Pol II 旋转。我们的结果为 Rat1 介导的酵母 Pol II 介导的 mRNA 转录终止以及其他真核生物的核外核酸酶介导的 mRNA 转录终止提供了结构机制。
