Structural Basis for pri-miRNA Recognition by Drosha

Mol Cell. 2020 May 7;78(3):423-433.e5. doi: 10.1016/j.molcel.2020.02.024. Epub 2020 Mar 27.

Abstract

A commencing and critical step in miRNA biogenesis involves processing of pri-miRNAs in the nucleus by Microprocessor. An important, but not completely understood, question is how Drosha, the catalytic subunit of Microprocessor, binds pri-miRNAs and correctly specifies cleavage sites. Here we report the cryoelectron microscopy structures of the Drosha-DGCR8 complex with and without a pri-miRNA. The RNA-bound structure provides direct visualization of the tertiary structure of pri-miRNA and shows that a helix hairpin in the extended PAZ domain and the mobile basic (MB) helix in the RNase IIIa domain of Drosha coordinate to recognize the single-stranded to double-stranded junction of RNA, whereas the dsRNA binding domain makes extensive contacts with the RNA stem. Furthermore, the RNA-free structure reveals an autoinhibitory conformation of the PAZ helix hairpin. These findings provide mechanistic insights into pri-miRNA cleavage site selection and conformational dynamics governing pri-miRNA recognition by the catalytic component of Microprocessor.

Keywords: DGCR8; Drosha; Microprocessor; cryo-EM; miRNA; pri-miRNA; structure.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cryoelectron Microscopy
  • Humans
  • MicroRNAs / chemistry*
  • MicroRNAs / metabolism*
  • Models, Molecular
  • Protein Conformation
  • Protein Domains
  • RNA-Binding Proteins / chemistry
  • RNA-Binding Proteins / genetics
  • RNA-Binding Proteins / metabolism
  • Ribonuclease III / chemistry*
  • Ribonuclease III / genetics
  • Ribonuclease III / metabolism*
  • Spodoptera / cytology

Substances

  • DGCR8 protein, human
  • MicroRNAs
  • RNA-Binding Proteins
  • DROSHA protein, human
  • Ribonuclease III