Cryo-EM structures of mouse full-length Dicer alone and in complex with Dicerdpre-miRNA reveal the molecular basis of locking Dicer in the closed state
(A) Domain architecture of full-length mouse Dicer numbered at boundaries.
(B) Overall structure of the full-length mouse Dicer, shown as 3.8-A ̊ cryo-EM density map and ribbon representations in two orthogonal views. Interface between the HEL1 and RNase IIIb domains is highlighted by a box.
(C) Overall structure of the full-length mouse Dicer-RNA complex, shown as 4.2-A ̊ cryo-EM density map and ribbon representations in two orthogonal views.
Richard Štefl and Petr Svoboda Research Groups
MicroRNA (miRNA) and RNA interference (RNAi) pathways rely on small RNAs produced by Dicer endonucle- ases. Mammalian Dicer primarily supports the essential gene-regulating miRNA pathway, but how it is spe- cifically adapted to miRNA biogenesis is unknown. We show that the adaptation entails a unique structural role of Dicer’s DExD/H helicase domain. Although mice tolerate loss of its putative ATPase function, the com- plete absence of the domain is lethal because it assures high-fidelity miRNA biogenesis. Structures of murine Dicerd–miRNA precursor complexes revealed that the DExD/H domain has a helicase-unrelated structural function. It locks Dicer in a closed state, which facilitates miRNA precursor selection. Transition to a cleav- age-competent open state is stimulated by Dicer-binding protein TARBP2. Absence of the DExD/H domain or its mutations unlocks the closed state, reduces substrate selectivity, and activates RNAi. Thus, the DExD/H domain structurally contributes to mammalian miRNA biogenesis and underlies mechanistical partitioning of miRNA and RNAi pathways.
Zapletal, D., Taborska, E., Pasulka, J., Malik, R., Kubicek, K., Zanova, M., Much, Ch., Sebesta, M. Buccheri, V., Horvat, F., Jenickova, I., Prochazkova, M., Prochazka, J., Pinkas, M., Novacek, J., Joseph, D. F., Sedlacek R., Bernecky C., O’Carrol, D., Stefl. R., and Svoboda, P.: Structural and functional basis of mammalian microRNA biogenesis by Dicer
Mol. Cell 2022, 82, 4064–4079, https://doi.org/10.1016/j.molcel.2022.10.010