Sarah C. Keane, Assistant Professor, Dept. of Biophysics and Dept. of Chemistry, University of Michigan, Ann Arbor, will give a talk on "Structural elucidation of the oncomiR-1 RNA."

ABSTRACT

Non-coding RNAs are key regulators of diverse biological processes in eukaryotes. MicroRNAs are a family of small non-coding RNAs that post-transcriptionally regulate gene expression in a sequence-dependent manner. Deviations from homeostatic microRNA expression levels, either reduced or enhanced expression, have been linked to cancers, diabetes, heart and neurodegenerative diseases, among others. To maintain proper microRNA expression levels, eukaryotic cells must tightly control the enzymatic processing of primary and precursor microRNA elements. However, the molecular determinants underlying this strict regulation of microRNA biogenesis are not fully understood. We are investigating the differential processing of oncomiR-1, a polycistronic primary microRNA that is enriched in many cancers. The oncomiR-1 transcript encodes six individual pre-miRNA hairpins that are processed differentially, resulting in a non-uniform abundance. Previous studies using chimeric primary transcripts, in which the pre-miRNA hairpin order has been shuffled, display disrupted processing of the pre-miRNAs. These data suggest that the higher order structure of oncomiR-1 helps regulate its processing. NPSL2 is an auxiliary hairpin within the oncomiR-1 transcript predicted to adopt multiple structures to regulate the processing of a downstream miR element. We have determined the structure of NPSL2 using NMR spectroscopy. Our studies suggest that NPSL2 is highly dynamic and we are currently investigating if the dynamics are linked to function. Protein binding partners identified via mass spectrometry are currently being validated as trans-acting regulators of miRNA biogenesis. Furthermore, we are expanding our structural studies to include the surrounding miR elements as we begin to build a comprehensive view of the oncomiR-1 structure.