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Mol Cell. 2018 Dec 7. pii: S1097-2765(18)30947-X. doi: 10.1016/j.molcel.2018.11.005. [Epub ahead of print]

Molecular Basis for the Single-Nucleotide Precision of Primary microRNA Processing.

Author information

1
Center for RNA Research, Institute for Basic Science, Seoul 08826, Korea; School of Biological Sciences, Seoul National University, Seoul 08826, Korea.
2
Center for RNA Research, Institute for Basic Science, Seoul 08826, Korea; Department of Life Sciences, Korea University, Seoul 02841, Korea. Electronic address: jaesungwoo@korea.ac.kr.
3
Center for RNA Research, Institute for Basic Science, Seoul 08826, Korea; School of Biological Sciences, Seoul National University, Seoul 08826, Korea. Electronic address: narrykim@snu.ac.kr.

Abstract

Microprocessor, composed of DROSHA and its cofactor DGCR8, initiates microRNA (miRNA) biogenesis by processing the primary transcripts of miRNA (pri-miRNAs). Here we investigate the mechanism by which Microprocessor selects the cleavage site with single-nucleotide precision, which is crucial for the specificity and functionality of miRNAs. By testing ∼40,000 pri-miRNA variants, we find that for some pri-miRNAs the cleavage site is dictated mainly by the mGHG motif embedded in the lower stem region of pri-miRNA. Structural modeling and deep-sequencing-based complementation experiments show that the double-stranded RNA-binding domain (dsRBD) of DROSHA recognizes mGHG to place the catalytic center in the appropriate position. The mGHG motif as well as the mGHG-recognizing residues in DROSHA dsRBD are conserved across eumetazoans, suggesting that this mechanism emerged in an early ancestor of the animal lineage. Our findings provide a basis for the understanding of miRNA biogenesis and rational design of accurate small-RNA-based gene silencing.

KEYWORDS:

DGCR8; DROSHA; RNase III; miRNA; microRNA

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