![]() They successfully captured six structures including the apo state of Dicer-2-Loqs-PD complex, the complex of Dicer-2-dsRNA-Loqs-PD in the initial binding pattern without ATP, the dsRNA-loading state and the active dicing state with ATP, and the WT Dicer-2-Loqs-PD complex in post-dicing state (Fig. 1 Using wild-type (WT) Dicer-2 and its mutant Dicer-2, with different combinations of assembly components, they carried out the structural analysis of the Dicer-2-Loqs-PD in the apo state and in multiple states. One of the two studies, from the teams of Jinbiao Ma, Fudan University, and Hongwei Wang, Tsinghua University, revealed the mechanism for the cycle of ATP-dependent dsRNA processing by Dicer-2-Loqs-PD. However, the dynamic molecular mechanism of how the Dicer-2 cleaves dsRNAs to generate siRNAs and how siRNAs are loaded into Ago2 in a defined orientation have not been fully elucidated. 4 So far, several biochemical and structural studies on Dicer proteins have been reported. 3 It’s known that Dicer-2 mediates the detection of virus-derived specific dsRNAs and the processing of these dsRNAs into siRNAs in antiviral RNAi responses. These siRNA duplexes are loaded into Argonaute2 (Ago2) protein with the aid of another partner protein, R2D2. By contrast, ATP-dependent Dicer-2 produces siRNA duplexes by cleaving long dsRNAs with the help of its cofactor Loquacious-PD (Loqs-PD). Dicer-1 interacts with the PB isoform of dsRBP Loquacious (Loqs-PB) to process microRNAs (miRNAs) precursors. 4 The Drosophila encodes two Dicers annotated as Dicer-1 and Dicer-2. 3 Dicer plays a vital role in cellular homeostasis and fighting virus infections. A canonical Dicer protein contains a helicase domain, a PAZ domain, a domain of unknown function (DUF283), two RNase III domains, and a dsRNA binding domain. Dicer, an RNase III enzyme, has a central role in producing siRNAs. SiRNAs are a crucial component for RNA interference (RNAi), a well-known gene expression regulation mechanism in various eukaryotes.
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