Poster abstracts

Poster number 43 submitted by Sicong Ma

Regulatory structural features of pre-miR-31 for Dicer processing

Sicong Ma (Department of Biophysics, University of Michigan), Anita Kotar (Slovenian NMR Centre, National Institute of Chemistry), Sarah C. Keane (Department of Biophysics and Department of Chemistry, University of Michigan)

microRNAs (miRs) are a class of non-coding RNA that post-transcriptionally regulates gene expression. Cleavage by Drosha converts primary microRNAs (pri-miRs) into precursor microRNAs (pre-miRs). Pre-miRNAs are subsequently cleaved by Dicer to generate mature miRs. Although many protein factors are known to regulate Dicer processing, how the intrinsic structure and stability of pre-miR affect Dicer processing are poorly understood, in part due to the limitation of high-resolution tertiary structures of this family of RNAs. Here, we determined the tertiary structure of pre-miR-31 using NMR spectroscopy. We show that an A∙C mismatch within the stem of pre-miR-31 stabilizes pre-miR-31 through the formation of an A+-C base pair near neutral pH. While mismatches within the stem of pre-miR-31 have little impact on Dicer processing, mismatches near the Dicer cleavage site can have significant impacts. We discovered that the presence of a single nucleotide mismatch structure near the cleavage site promotes Dicer processing and 5’ strand cleavage while the larger internal loop structures hinder this processing. Meanwhile, we observed that apical loop size could regulate Dicer processing efficiency bidirectionally, and that loop size needs to be optimized for efficient short hairpin RNA (shRNA) design. Furthermore, we reveal that the top three base pairs of pre-miR-31 are a finely-tuned intrinsic structural feature that helps promote optimal binding and processing by Dicer.

Keywords: pre-miR-31, regulatory structural feature, Dicer processing