Selective regulatory and biogenesis mechanisms for microRNAs

PROJECT ABSTRACT microRNAs (miRNAs) are an abundant class of small regulatory RNAs that typically derive from stepwise cleavages of hairpin transcripts by the Drosha and Dicer RNase III enzymes. The resulting mature miRNAs mediate extensive networks of post- transcriptional regulation, and are implicated in a variety of diseases including cancer. This proposal extends our long-standing commitment to understand atypical and regulated strategies for microRNA biogenesis and function. We build on long-standing research efforts in the lab, as well as very recent developments and knowledge, to propose three parallel directions on miRNA regulation. First, we will dissect regulatory interactions within a miRNA operon, by which an optimal miRNA hairpin can benefit the biogenesis of a neighboring suboptimal member (miRNA cluster assistance). Second, we will uncover how multiple RNA quality control strategies suppress the biogenesis of adventitious miRNA hairpin substrates derived from splicing (mirtrons and splicing- derived, structured RNAs). These may play broad and unrecognized roles in regulating host gene splicing. Third, we introduce data on a novel repressor of miRNA accumulation and function (Alas), and endeavor to place its activity Our studies utilize a wide variety of experimental and computational techniques, and employ both Drosophila and mammalian systems. The data and insights gained from this grant will extend fundamental knowledge on small RNA pathways, have potential to help interpret genetic diseases involving miRNA dysfunction, and may eventually underlie improved methods for therapeutic RNAi.