miRNAs are one of the key post-transcriptional regulators of gene expression and play a role in a wide range of biological processes including development, cell proliferation, cell differentiation, metabolism and apoptosis. We have previously deduced the mechanism and relative timing of several cellular events during miRNA- induced translational repression. Here, we will focus on elucidating mechanisms that modulate this regulatory pathway. Variations in the level of miRNA-induced gene regulation are observed in both reporter and global- based approaches, leading us to ask why and how these differences exist. Using our inducible and controllable in vivo reporter systems, as well as in vitro techniques, we will investigate the effects of mRNA target intrinsic stability on the kinetic and dissect contributions of miRICS components in the process of miRNA-mediated gene silencing. We will employ this system with a variety of modified and natural reporter genes to get a more complete picture of the relationships between distinct RNA binding proteins and miRNA pathway components on gene regulation. We will use our newly developed assays and techniques to deduce the molecular mechanisms for modulation of miRNA-mediated gene silencing by these RNA-binding proteins. Finally, these studies will be followed by genome-wide approaches in a biological context that will allow us to investigate the importance of cis and trans factors on the modulation of specific miRNA response across endogenous gene targets. In addition to vastly expanding our knowledge about miRNA-mediated gene silencing, the proposed work will give us more clues as to how alterations in systems that modulate miRNA response may influence cellular homeostasis in regular and pathological states.