RNA interactions and dynamics of the miRNA processing associated protein HYL1

MORGADA MN; MATEOS J; BOISBOUVIER J; PALATNIK JF; RASIA RM

Salta

Congreso; 3rd Latin American Protein Society Meeting; 2010

MicroRNAs (miRNAs), a key member of the family of small non-coding RNA regulators, are 21 nucleotide (nt) molecules processed from endogenous transcripts. The biogenesis of miRNAs is a complex process, which differs in plants and animals. miRNA precursors (pri-miRNAs) are transcribed in the nucleus by RNA polymerase II. The actual miRNAs are located within stem-loop structures in the pri-miRNA and are released through the action of RNase III-type enzymes of the Dicer family. DICER-LIKE1 (DCL1) excises the mature miRNA in plants in a stepwise manner aided by the dsRNA-binding protein HYL1 and the zinc-finger protein SERRATE.HYL1 is a double-stranded RNA binding protein harbouring two double stranded RNA binding domains (dsRBDs), involved in miRNA processing in plants. HYL1 enhances the efficiency and the precision of the RNase III protein DCL1. Here we show the solution structure of both dsRBDs of HYL1 and a dissection of the contributions of the domains of HYL1 to the binding of RNA targets. We found that the first dsRBD is the main contributor to RNA binding. Mapping of the interaction regions by NMR on the structure of HYL1 RNA-binding domains showed that the difference in binding capabilities can be traced to sequence divergence in loop beta2-beta3. The characterization by NMR of ps-ns motions of the first dsRBD shows that regions participating in RNA binding are more flexible than average, suggesting a correlation between flexibility and RNA binding activity.