The Drosha-DGCR8 complex in primary microRNA processing
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TLDR
It is shown that DGCR8 may be an essential component of the pri-miRNA processing complex, along with Drosha, and a model for the action mechanism of class II RNase III proteins is proposed.Abstract:
RNase III proteins play key roles in microRNA (miRNA) biogenesis. The nuclear RNase III Drosha cleaves primary miRNAs (pri-miRNAs) to release hairpin-shaped pre-miRNAs that are subsequently cut by the cytoplasmic RNase III Dicer to generate mature miRNAs. While Dicer (class III) and other simple RNase III proteins (class I) have been studied intensively, the class II enzyme Drosha remains to be characterized. Here we dissected the action mechanism of human Drosha by generating mutants and by characterizing its new interacting partner, DGCR8. The basic action mechanism of Drosha was found to be similar to that of human Dicer; the RNase III domains A and B form an intramolecular dimer and cleave the 3 and 5 strands of the stem, respectively. Human Drosha fractionates at ∼650 kDa, indicating that Drosha functions as a large complex. In this complex, Drosha interacts with DGCR8, which contains two double-stranded RNA (dsRNA)-binding domains. By RNAi and biochemical reconstitution, we show that DGCR8 may be an essential component of the pri-miRNA processing complex, along with Drosha. Based on these results, we propose a model for the action mechanism of class II RNase III proteins.read more
Citations
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References
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TL;DR: Although they escaped notice until relatively recently, miRNAs comprise one of the more abundant classes of gene regulatory molecules in multicellular organisms and likely influence the output of many protein-coding genes.
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Role for a bidentate ribonuclease in the initiation step of RNA interference
TL;DR: Dicer is a member of the RNase III family of nucleases that specifically cleave double-stranded RNAs, and is evolutionarily conserved in worms, flies, plants, fungi and mammals, and has a distinctive structure, which includes a helicase domain and dualRNase III motifs.
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The nuclear RNase III Drosha initiates microRNA processing
Yoontae Lee,Chiyoung Ahn,Jinju Han,Hyounjeong Choi,Jaekwang Kim,Jeongbin Yim,Junho Lee,Patrick Provost,Olof Rådmark,Sun-Young Kim,V. Narry Kim +10 more
TL;DR: The two RNase III proteins, Drosha and Dicer, may collaborate in the stepwise processing of miRNAs, and have key roles in miRNA-mediated gene regulation in processes such as development and differentiation.
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MicroRNA genes are transcribed by RNA polymerase II.
TL;DR: The first direct evidence that miRNA genes are transcribed by RNA polymerase II (pol II) is presented and the detailed structure of a miRNA gene is described, for the first time, by determining the promoter and the terminator of mir‐23a∼27a‐24‐2.
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RNA interference is mediated by 21- and 22-nucleotide RNAs
TL;DR: In this article, the authors demonstrate that 21 and 22-nt RNA fragments are the sequence-specific mediators of RNA interference in a Drosophila in vitro system, and provide evidence that the direction of dsRNA processing determines whether sense or antisense target RNA can be cleaved by the siRNA-protein complex.