RRM
2013 Rustbelt RNA Meeting
RRM
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Talk abstracts
Abstract:
The microprocessor, comprised of DGCR8 and Drosha, cleaves primary microRNA (miRNA) hairpins to generate pre-miRNAs, which are subsequently processed to a mature miRNAs. In addition to pri-miRNA hairpins, other regions within coding genes can form RNA hairpins. Increasing evidence indicates that the microprocessor may bind indiscriminately to RNA hairpins, resulting in widespread cleavage of RNA. Prevalent cleavage of RNA by the microprocessor has the potential to impact gene expression and pre-mRNA alternative splicing. Here, we identify the small, alternative exon 5 in the eIF4H gene as a microprocessor substrate. Using a cell-free cleavage assay, we find that this exon is processed into a pre- and mature miRNA by the microprocessor and Dicer, respectively. We also detect the small RNAs generated by the microprocessor in cells. Although cleavage of the exon precludes its inclusion in mRNA, we found that overexpression of Drosha, both wild-type and a mutant form that can bind but not cleave RNA, promotes the inclusion of this alternative exon in a manner that is dependent on RNA structure. This Drosha-mediated increase in exon inclusion is accompanied by non-canonical cleavage within the exon. Additionally, Drosha may be in competition with the SRSF2 and 3 proteins, which are negative regulators of both exon 5 inclusion in the mRNA and the non-canonical cleavage event. These results indicate a previously unknown role for the microprocessor in promoting splicing that may occur through competition with canonical splicing factors and the role in splicing may be in conflict with its role in miRNA biogenesis.
Keywords: Alternative splicing, microRNA, Microprocessor
