Poster abstracts

Poster number 31 submitted by Mallory Havens

Biogenesis of Mammalian microRNAs by a Non-Canonical Processing Pathway

Mallory A. Havens (Department of Cell Biology and Anatomy, Chicago Medical School at Rosalind Franklin University), Ashley A. Reich (Biology Department, Lake forest College), Dominik M. Duelli (Department of Cellular and Molecular Pharmacology, Chicago Medical School at Rosalind Franklin University), Michelle L. Hastings (Department of Cell Biology and Anatomy, Chicago Medical School at Rosalind Franklin University)

Abstract:
Canonical microRNA biogenesis requires the Microprocessor components, Drosha and DGCR8, to generate precursor-miRNA, and Dicer to form mature miRNA. The Microprocessor is not required for processing of some miRNAs, including mirtrons, which are excised from introns by the spliceosome and subsequently cleaved by Dicer to form mature miRNAs. In this study, we examine the processing of putative human mirtrons and demonstrate that, although some are splicing-dependent, as expected, the predicted mirtrons, miR-1225 and miR-1228, are produced in the absence of splicing. Remarkably, biogenesis of these splicing-independent mirtron-like miRNAs, termed “simtrons”, requires Drosha but not the other canonical miRNA biogenesis components, DGCR8, Dicer, Exportin-5 or Argonaute 2. Both simtrons and mirtrons function in silencing of target transcripts as demonstrated by luciferase assays and interact with all of the argonaute proteins of the RISC complex as demonstrated by immunoprecipitation assays. These findings reveal a non-canonical miRNA biogenesis pathway that can produce functional regulatory RNAs.

Keywords: microRNA biogenesis, splicing, mirtron