A complex of Drosha with DGCR8 (or its homolog Pasha) cleaves primary microRNA (pri-miRNA) substrates into precursor miRNA and initiates the microRNA maturation process. Drosha provides the catalytic site for this cleavage, whereas DGCR8 or Pasha provides a frame for anchoring substrate pri-miRNAs. To clarify the molecular basis underlying recognition of pri-miRNA by DGCR8 and Pasha, we determined the crystal structure of the human DGCR8 core (DGCR8S, residues 493–720). In the structure, the two double-stranded RNA–binding domains (dsRBDs) are arranged with pseudo two-fold symmetry and are tightly packed against the C-terminal helix. The H2 helix in each dsRBD is important for recognition of pri-miRNA substrates. This structure, together with fluorescent resonance energy transfer and mutational analyses, suggests that the DGCR8 core recognizes pri-miRNA in two possible orientations. We propose a model for DGCR8's recognition of pri-miRNA.
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We thank H.S. Lee and K.H. Kim for help with the data collection (beamline PAL4A) and J.H. Yu, S. Jeong, T.H. Joo, K.Y. Choi and H. Jeon for their valuable comments. This work was supported by the National Creative Research Initiative Program (Korean Ministry of Science and Technology) and the BK21 Program.
The authors declare no competing financial interests.
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Sohn, S., Bae, W., Kim, J. et al. Crystal structure of human DGCR8 core. Nat Struct Mol Biol 14, 847–853 (2007). https://doi.org/10.1038/nsmb1294
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