Structural Basis for pri-miRNA Recognition by Drosha

Area of Science:

• Molecular Biology
• Structural Biology
• Biochemistry

Background:

• MicroRNA (miRNA) biogenesis is crucial for gene regulation.
• The Microprocessor complex, containing Drosha and DGCR8, initiates miRNA production by processing pri-miRNAs.
• The precise mechanism of Drosha-pri-miRNA binding and cleavage site selection remains incompletely understood.

Purpose of the Study:

• To elucidate the structural basis of Drosha-DGCR8 complex interaction with pri-miRNA.
• To understand how Drosha recognizes and binds pri-miRNA substrates.
• To investigate the conformational dynamics of Drosha during pri-miRNA processing.

Main Methods:

• Cryo-electron microscopy (cryo-EM) was used to determine the structures of the Drosha-DGCR8 complex.
• Structures were obtained both with and without a bound pri-miRNA.
• Detailed structural analysis of protein-RNA interactions was performed.

Main Results:

• The cryo-EM structure of the RNA-bound complex visualizes pri-miRNA tertiary structure.
• Drosha's PAZ domain helix hairpin and RNase IIIa domain MB helix recognize the RNA single-stranded to double-stranded junction.
• The dsRNA binding domain interacts extensively with the RNA stem.
• The RNA-free structure reveals an autoinhibitory conformation of the PAZ helix hairpin.

Conclusions:

• The study provides direct structural evidence for pri-miRNA recognition by Drosha.
• Mechanistic insights into pri-miRNA cleavage site selection by the Microprocessor complex are offered.
• Conformational dynamics of Drosha are key to substrate recognition in miRNA biogenesis.