The structure of plant pri-miR172 and its complex with HYL1

SUAREZ IP; HÖBARTNER C; RASIA RM

Villa Carlos Paz

Congreso; XLII Reunión Anual de la Sociedad Argentina de Biofísica; 2013

Sociedad Argentina de Biofísica

MicroRNAs are essential gene regulators in multicellular organisms. Plant miRNA precursors (pri-miRNAs) are processed in the nucleus by a protein complex formed by DICER-LIKE1 (DCL1), HYL1 and SERRATE. HYL1 is a double stranded RNA binding protein, with no catalytic activity, that ensures the accuracy of the processing reaction. The mechanism by which it guides the RNAse DCL1 to the correct location within the precursor is unknown. pri-miRNAs display highly variable secondary structure features that could be essential to define the location of the miRNAs within their sequences. In this work we characterized the secondary structure of Arabidopsis thaliana pri-miR172 and a variant that hinders processing in vivo by means of enzymatic probing. The mutant shows an alteration in the secondary structure distribution of the upper stem. We mapped the location of HYL1 within the precursor by RNAse and DMS protection assays. The protein binds to the lower stem of the precursor, and the size of the protected region suggests that both RNA binding domains bind in line on the precursor. Binding of HYL1 induces conformational changes on the upper stem region. Remarkably, the first nucleotide of the miRNA sequence becomes particularly sensitive to DMS modification in the complex with HYL1. Altogether our results show that HYL1 recognizes specifically the pri-miRNA structure and induces conformational changes on distant parts of the precursor that contribute to the specificity of the processing reaction.