MOLECULAR INSIGHTS INTO MIRNA PROCESSING BY ARABIDOPSIS THALIANA SERRATE AND DAWDLE

Abstract

SE and HYL1 are known to direcly improve the rate and accuracy of the processing by DCL1 both in vitro and in vivo. DDL was recently reported to help processing of pri-miRNA in vivo but apart from SE and HYL1. Here we report the crystal structure of Arabidopsis SE core (residues 194-543) at 2.7Å and DDL FHA domain (residues 180-314) at 2.0Å. SE core adopts the ¿walking man-like¿ topology with amino-terminal a-helix, Middle and caboxyl-terminal zinc-finger domains. Pull-down assay shows that SE core provides the platform for HYL1 and DCL1 binding, whereas in vitro RNA binding and in vivo mutant rescue experiments suggest that the non-canonical zinc finger domain coupled with carboxyl-terminal tail binds miRNA precursors. The crystal structure of DDL FHA domain reveals ß-sandwich architecture with outwardly emanating loops, and suggests the loop region connecting the strands forming ß-sandwich of DDL FHA domain serves phospho-recognition.