THE DOUBLE-STRANDED RNA BINDING DOMAINS OF DCL1: NON-CANONNICAL FEATURES ON A COMMON MOTIF

RASIA RM; BURDISSO P; SUAREZ IP; BOLOGNA NG; PALATNIK JF; BOISBOUVIER J; BESRCH B

Viena

Conferencia; 23rd International Conference on Arabidopsis Research (ICAR); 2012

MicroRNAs are essential gene regulators in multicellular organisms. Plant miRNAs are processed in the nucleus by a protein complex formed by DICER-LIKE1 (DCL1), HYL1 and SERRATE. DCL1 has a central role in the recognition and processing of the heterogeneous plant precursors, yet little is known about the structural aspects of this protein. We present a structural characterization of the two double-stranded RNA binding domains (dsRBDs) of DCL1, which are presumed to participate in pri-miRNA recognition and binding. The first dsRBD is intrinsically disordered, but folds upon binding substrate RNA. We solved the solution structure of the second dsRBD, and found that it has a canonical fold but bears some variation with respect to other homologous domains. In constrast with canonical dsRBDs both domains from DCL1 bind dsDNA with a similar affinity as dsRNA. Analysis of the sequences of the C-terminal dsRBDs present in DCL1-4 proteins from different plants shows a much higher conservation among DCL1 homologs. This suggests that the peculiar properties of this double domain were conserved through evolution, and that they have to be essential for pri-miRNA processing by DCL1. Our characterization of DCL1 dsRBDs show that these domains should have functions other than substrate recognition and binding, which are conferred by their unusual structural features.