Tuan Anh Nguyen,1,2 Myung Hyun Jo,3,4,5 Yeon-Gil Choi,v1,2 Joha Park,1,2 S. Chul Kwon,1,2 Sungchul Hohng,3,4,5,6 V. Narry Kim,1,2,* and Jae-Sung Woo1,2,*
1Center for RNA Research, Institute for Basic Science, Seoul 151-742, Korea
2School of Biological Sciences
3Department of Physics and Astronomy
4National Center for Creative Research Initiatives
5Institute of Applied Physics
6Department of Biophysics and Chemical Biology
Seoul National University, Seoul 151-742, Korea
*Correspondence: V. Narry Kim, Jae-Sung Woo
Summary
MicroRNA (miRNA) maturation is initiated by Microprocessor composed of RNase III DROSHA and its cofactor DGCR8, whose fidelity is critical for generation of functional miRNAs. To understand how Microprocessor recognizes pri-miRNAs, we here reconstitute human Microprocessor with purified recombinant proteins. We find that Microprocessor is an ∼364 kDa heterotrimeric complex of one DROSHA and two DGCR8 molecules. Together with a 23-amino acid peptide from DGCR8, DROSHA constitutes a minimal functional core. DROSHA serves as a “ruler” by measuring 11 bp from the basal ssRNA-dsRNA junction. DGCR8 interacts with the stem and apical elements through its dsRNA-binding domains and RNA-binding heme domain, respectively, allowing efficient and accurate processing. DROSHA and DGCR8, respectively, recognize the basal UG and apical UGU motifs, which ensure proper orientation of the complex. These findings clarify controversies over the action mechanism of DROSHA and allow us to build a general model for pri-miRNA processing.