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Cryo-EM Structures of Human Drosha and DGCR8 in Complex with Primary MicroRNA

Alexander C Partin1, Kaiming Zhang2, Byung-Cheon Jeong1

  • 1Laboratory of RNA Biology, Cecil H. and Ida Green Center for Reproductive Biology Sciences, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA; Departments of Biophysics and Obstetrics and Gynecology, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA.

Molecular Cell
|March 30, 2020
PubMed

Insights

Human Microprocessor complex structure reveals how it recognizes pri-miRNA. This structural insight explains the molecular basis for microRNA processing accuracy and efficiency.

Area of Science:

  • Molecular Biology
  • Structural Biology
  • Biochemistry

Background:

  • Metazoan microRNA (miRNA) biogenesis requires the Microprocessor complex, composed of Drosha and DGCR8.
  • The structural basis for Microprocessor recognition of primary miRNA transcripts (pri-miRNAs) remains elusive.
  • Understanding this interaction is crucial for elucidating miRNA maturation pathways.

Purpose of the Study:

  • To determine the cryo-electron microscopy (cryo-EM) structure of human Microprocessor bound to a pri-miRNA.
  • To elucidate the molecular mechanisms by which Microprocessor recognizes pri-miRNA and identifies the cleavage site.
  • To provide a structural basis for the efficiency and accuracy of pri-miRNA processing.

Main Methods:

  • Cryo-electron microscopy (cryo-EM) to resolve the structure of the human Microprocessor complex.
  • Co-crystallization and structural analysis of Microprocessor with a docked pri-miRNA.
  • Structural comparison of fully and partially docked states to understand domain dynamics.

Main Results:

  • A cryo-EM structure reveals human Microprocessor with a pri-miRNA docked in the active site.
  • Drosha's Belt and Wedge regions recognize the basal junction of pri-miRNA, clamping over single-stranded RNA (ssRNA).
  • Double-stranded RNA-binding domains (dsRBDs) act as a molecular ruler to measure stem length, ensuring accurate cleavage site identification.

Conclusions:

  • The study provides a molecular model for how Microprocessor recognizes pri-miRNA transcripts.
  • Structural details reveal the mechanism for accurate cleavage site selection during miRNA processing.
  • These findings advance our understanding of the fundamental steps in microRNA biogenesis.
Keywords:
DGCR8DroshaMicroprocessorRNA processingRNase IIIcryo-EMdsRBDmicroRNApri-miRNAstructure

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