4.8 Article

Structural insights into dsRNA processing by Drosophila Dicer-2-Logs-PD

Journal

NATURE
Volume 607, Issue 7918, Pages 399-+

Publisher

NATURE PORTFOLIO
DOI: 10.1038/s41586-022-04911-x

Keywords

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Funding

  1. National Natural Science Foundation of China [31971130, 31825009, 32000849, 91940302]
  2. National Key R&D Program of China [2017YFA0503500]
  3. mRNA Innovation and Translation Center, Shanghai
  4. Xplorer Prize

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This study revealed the molecular mechanism for the full cycle of ATP-dependent dsRNA processing by Dcr-2-Loqs-PD. The structures of Dcr-2-Loqs-PD in various states during dsRNA processing were determined using cryo-electron microscopy. The study elucidated the conformational changes and interactions between Dcr-2 and Loqs-PD, providing insights into the RNA interference mechanism and potential therapeutic strategies for related diseases.
Small interfering RNAs (siRNAs) are the key components for RNA interference (RNAi), a conserved RNA-silencing mechanism in many eukaryotes(1,2). In Drosophila, an RNase III enzyme Dicer-2 (Dcr-2), aided by its cofactor Loquacious-PD (Loqs-PD), has an important role in generating 21 bp 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 duplexes(5,6). 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 50 bp 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 21 bp siRNA duplex as confirmed by the structure in the post-dicing state. Collectively, this study revealed the molecular mechanism for the full cycle ofATP-dependent dsRNA processing by Dcr-2-Loqs-PD.

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