小柯机器人

复旦大学麻锦彪和清华大学王宏伟等研究人员合作揭示果蝇Dicer-2-Loqs-PD加工dsRNA的结构基础。相关论文于2022年6月29日在线发表于国际学术期刊《自然》。

研究人员表示，小干扰RNA（siRNA）是RNA干扰（RNAi）的关键成分，是许多真核生物中一种保守的RNA沉默机制。在果蝇中，RNase III酶Dicer-2（Dcr-2）在其辅助因子Loquacious-PD（Loqs-PD）的帮助下，在从长双链RNA（dsRNA）生成21bp的siRNA双链中起着重要作用。Dcr-2的螺旋酶结构的ATP水解对于成功地将长的dsRNA加工成连续的siRNA双链体至关重要。

研究人员报告了Dcr-2-Loqs-PD在apo状态和加工50bp dsRNA底物的多种状态下的冷冻电镜结构。这些结构阐明了Dcr-2和Loqs-PD之间的相互作用，以及Dcr-2在处理dsRNA的周期中的大量构象变化。在最初的dsRNA结合后，N端螺旋酶和未知功能域283（DUF283）域发生了构象变化，形成了一个ATP结合袋和一个5′-磷酸盐结合袋。在有ATP的情况下，Dcr-2-Loqs-PD的整体构象在沿着dsRNA转运过程中是相对刚性的，而DUF283和RIIIDb结构域之间的相互作用通过阻止dsRNA进入RNase活性中心来防止转运过程中的非特异性切割。额外的ATP依赖性构象变化需要形成活性切割状态，并精确地将dsRNA切割成21bp的siRNA双链，这一点在切割后的结构中得到证实。

总之，这项研究揭示了Dcr-2-Loqs-PD对ATP依赖性dsRNA进行完整周期加工的分子机制。

附：英文原文

Title: Structural insights into dsRNA processing by Drosophila Dicer-2–Loqs-PD

Author: Su, Shichen, Wang, Jia, Deng, Ting, Yuan, Xun, He, Jinqiu, Liu, Nan, Li, Xiaomin, Huang, Ying, Wang, Hong-Wei, Ma, Jinbiao

Issue&Volume: 2022-06-29

Abstract: Small interfering RNAs (siRNAs) are the key components for RNA interference (RNAi), a conserved RNA-silencing mechanism in many eukaryotes1,2. In Drosophila, an RNase III enzyme Dicer-2 (Dcr-2), aided by its cofactor Loquacious-PD (Loqs-PD), has an important role in generating 21bp siRNA duplexes from long double-stranded RNAs (dsRNAs)3,4. ATP hydrolysis by the helicase domain of Dcr-2 is critical to the successful processing of a long dsRNA into consecutive siRNA duplexes5,6. Here we report the cryo-electron microscopy structures of Dcr-2–Loqs-PD in the apo state and in multiple states in which it is processing a 50bp dsRNA substrate. The structures elucidated interactions between Dcr-2 and Loqs-PD, and substantial conformational changes of Dcr-2 during a dsRNA-processing cycle. The N-terminal helicase and domain of unknown function 283 (DUF283) domains undergo conformational changes after initial dsRNA binding, forming an ATP-binding pocket and a 5′-phosphate-binding pocket. The overall conformation of Dcr-2–Loqs-PD is relatively rigid during translocating along the dsRNA in the presence of ATP, whereas the interactions between the DUF283 and RIIIDb domains prevent non-specific cleavage during translocation by blocking the access of dsRNA to the RNase active centre. Additional ATP-dependent conformational changes are required to form an active dicing state and precisely cleave the dsRNA into a 21bp siRNA duplex as confirmed by the structure in the post-dicing state. Collectively, this study revealed the molecular mechanism for the full cycle of ATP-dependent dsRNA processing by Dcr-2–Loqs-PD.

DOI: 10.1038/s41586-022-04911-x

Source: https://www.nature.com/articles/s41586-022-04911-x

Nature：《自然》，创刊于1869年。隶属于施普林格·自然出版集团，最新IF：69.504
官方网址：http://www.nature.com/
投稿链接：http://www.nature.com/authors/submit_manuscript.html