Cryo-EM reveals the structural basis for the regulatory function of HEL1 domain in vertebrate DICERs

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Authors

ZAPLETAL David KUBÍČEK Karel ZÁNOVÁ Martina MALIK Radek ŠEBESTA Marek NOVÁČEK Jiří SVOBODA Petr ŠTEFL Richard

Year of publication 2022
Type Appeared in Conference without Proceedings
MU Faculty or unit

Faculty of Science

Citation
Description Dicer is RNase III enzyme producing small RNA in RNA silencing pathways. In mice, there are two isoforms that differ by presence or absence of the N-terminal HEL1 domain. The full-length Dicer acts in microRNA (miRNA) biogenesis while the truncated version, present in oocytes (DicerO), generates small interfering RNAs (siRNA) in RNA interference (RNAi) pathway. While models for siRNA and miRNA processing by vertebrate Dicer have emerged from the structural and biochemical studies, the active dicing state in Dicer-RNA structures has not been structurally characterized yet. In this study we used cryo-electron microscopy, AI-based prediction, and biochemical approaches to understand the structural difference between Dicer and DicerO, explaining their different in vivo functions. We observed that Dicer-RNA complex exists prevalently in an inactive, pre-dicing state (Fig.1b), while DicerO-RNA was observed almost exclusively in dicing-state (Fig.2c), revealing the molecular principles of substrate selection and enzymatic activity. Our data suggest HEL1 role in Dicer activity and substrate specificity by regulation of the loading of RNA substrate.
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