Key Laboratory of Molecular Design for Plant Cell Factory of Guangdong Higher Education Institutes, Institute of Plant and Food Science, Department of Biology, School of Life Sciences, Southern University of Science and Technology, Shenzhen 518055, China.
Department of Biochemistry and Molecular Biology, International Cancer Center, Shenzhen University Medical School, Shenzhen 518060, China.
Science. 2023 Mar 24;379(6638):1209-1213. doi: 10.1126/science.adf8231. Epub 2023 Mar 9.
In addition to the conserved RNA polymerases I to III (Pols I to III) in eukaryotes, two atypical polymerases, Pols IV and V, specifically produce noncoding RNA in the RNA-directed DNA methylation pathway in plants. Here, we report on the structures of cauliflower Pol V in the free and elongation conformations. A conserved tyrosine residue of NRPE2 stacks with a double-stranded DNA branch of the transcription bubble to potentially attenuate elongation by inducing transcription stalling. The nontemplate DNA strand is captured by NRPE2 to enhance backtracking, thereby increasing 3'-5' cleavage, which likely underpins Pol V's high fidelity. The structures also illuminate the mechanism of Pol V transcription stalling and enhanced backtracking, which may be important for Pol V's retention on chromatin to serve its function in tethering downstream factors for RNA-directed DNA methylation.
除了真核生物中保守的 RNA 聚合酶 I 到 III（Pol I 到 III）之外，两种非典型的聚合酶 Pols IV 和 V，特异性地在植物的 RNA 指导的 DNA 甲基化途径中产生非编码 RNA。在这里，我们报告了在自由和延伸构象中的花椰菜 Pol V 的结构。NRPE2 的保守酪氨酸残基与转录泡的双链 DNA 分支堆叠，可能通过诱导转录停滞来减弱延伸。非模板 DNA 链被 NRPE2 捕获，以增强回溯，从而增加 3'-5' 切割，这可能是 Pol V 高保真度的基础。这些结构还阐明了 Pol V 转录停滞和增强回溯的机制，这对于 Pol V 在染色质上的保留以发挥其在连接 RNA 指导的 DNA 甲基化下游因子方面的功能可能很重要。
