The RNA-induced silencing pathway regulates gene expression by inducing translational repression and/or activating degradation of targeted mRNAs. Aberrations in this pathway are increasingly observed in human diseases, including cancer, as represented by the discovery of oncogenic miRNAs, known as oncomirs. This pathway requires a ~22nt small RNA molecule known as a micro (mi) RNA to guide the RNA-induced silencing complex (RISC) to the targeted mRNA. However, many of the factors that are required for the silencing pathway to progress are not well understood, including the ATPase MOV10. MOV10 interacts with miRNA-containing complexes and is believed to be required for miRNA- induced silencing, however, the precise molecular function of MOV10, and its ATPase activity, remain uncharacterized. Additionally, MOV10 is a close homolog of the mRNP-remodeling factor, Upf1, which remodels RNA-protein complexes as a prerequisite to the RNA-processing event known as nonsense mediated decay. I hypothesize that MOV10 acts analogously to Upf1 during the RNA-induced silencing pathway to remodel the RNA-protein complexes and facilitate progression of this pathway. The goal of the work proposed here is to understand the role of MOV10 in the mRNA silencing pathway by (1) determining the step(s) at which MOV10 is required in RNA-induced silencing and (2) investigating the role of the ATPase domain of MOV10 in the context of endogenous MOV10 targets. The importance of MOV10 in mRNA silencing in human cells will be addressed by analyzing the global and biochemical effects of MOV10 depletion on small RNA production, RISC maturation, translational repression of mRNPs, and mRNA decay. Next, the ATPase function of MOV10 will be studied by using ATPase mutants of MOV10 to test for accumulation of mRNPs and miRNPs with the hypothesis that MOV10 ATPase is required for a remodeling event. Elucidating how MOV10 facilitates RNA-induced silencing will add to our general understanding of mRNA silencing, and is likely to provide novel insights into how mechanistic errors in mRNA silencing may lead to human disease.
Aberrant expression of miRNAs and misregulation of the miRNA-silencing pathway are commonly observed in different types of human disease and in some cases have the capacity to transform normal human cells. To determine how we can potentially target the miRNA-silencing pathway with novel therapeutics, it is crucial to first understand the molecular composition of miRNA- associated complexes and the molecular function of their components. The studies described in this proposal will significantly advance our current understanding of the RNA-induced silencing pathway by assigning mechanistic function to MOV10, a factor known to be essential to RNA-induced silencing of mRNAs.