Crystal structure of human DGCR8 core

Area of Science:

• Molecular Biology
• Structural Biology
• Biochemistry

Background:

• The Drosha-DGCR8 complex initiates microRNA (miRNA) maturation by cleaving primary miRNA (pri-miRNA).
• Drosha possesses the catalytic activity, while DGCR8 (or Pasha) anchors the pri-miRNA substrate.
• Understanding DGCR8's substrate recognition mechanism is key to elucidating miRNA biogenesis.

Purpose of the Study:

• To determine the crystal structure of the human DGCR8 core (DGCR8S).
• To elucidate the molecular basis of pri-miRNA recognition by DGCR8.
• To propose a model for DGCR8-pri-miRNA interaction.

Main Methods:

• X-ray crystallography to determine the structure of human DGCR8 core (residues 493-720).
• Fluorescent resonance energy transfer (FRET) analysis.
• Site-directed mutagenesis studies.

Main Results:

• The crystal structure revealed a pseudo two-fold symmetry in the arrangement of DGCR8's two double-stranded RNA-binding domains (dsRBDs).
• The H2 helix within each dsRBD was identified as critical for pri-miRNA substrate recognition.
• Structural and biochemical data suggest DGCR8 recognizes pri-miRNA in two distinct orientations.

Conclusions:

• The determined structure provides insights into the molecular architecture of the DGCR8 core.
• DGCR8 employs its dsRBDs, particularly the H2 helix, for pri-miRNA binding.
• A model for DGCR8-mediated pri-miRNA recognition is proposed, advancing understanding of miRNA processing.