MicroRNA maturation is initiated by RNase III DROSHA that cleaves the stem loop of primary microRNA. DROSHA functions together with its cofactor DGCR8 in a heterotrimeric complex known as Microprocessor. Here, we report the X-ray structure of DROSHA in complex with the C-terminal helix of DGCR8. We find that DROSHA contains two DGCR8-binding sites, one on each RNase III domain (RIIID), which mediate the assembly of Microprocessor. The overall structure of DROSHA is surprisingly similar to that of Dicer despite no sequence homology apart from the C-terminal part, suggesting that DROSHA may have evolved from a Dicer homolog. DROSHA exhibits unique features, including non-canonical zinc-finger motifs, a long insertion in the first RIIID, and the kinked link between Connector helix and RIIID, which explains the 11-bp-measuring "ruler" activity of DROSHA. Our study implicates the evolutionary origin of DROSHA and elucidates the molecular basis of Microprocessor assembly and primary microRNA processing.
Bibliographical noteFunding Information:
We thank the beamline staffs at the Pohang Accelerator Laboratory for assistance with data collection. This work was supported by IBS-R008-D1 of Institute for Basic Science from the Ministry of Science, ICT, and Future Planning of Korea (S.C.K., T.A.N., Y.-G.C., J.-S.W., and V.N.K.) and Creative Research Initiatives (2009-0081562) of the National Research Foundation of Korea (M.H.J. and S.H.).
© 2016 Elsevier Inc.
ASJC Scopus subject areas
- General Biochemistry,Genetics and Molecular Biology