Systematic analysis of antiviral microRNA function

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In this proposal we examine how specific molecules, microRNAs, limit the capacity of viruses to replicate in host cells. Viruses (by definition) require host proteins to enter a cell, replicate and spread in an animal; microRNAs regulate the expression level of these proteins. We have previously demonstrated that certain host microRNAs suppress replication of multiple herpesviruses (cytomegalovirus, herpes simples virus-1 and mouse gammaherpesvirus) as well as an unrelated single stranded RNA virus, Semlikiforest virus. We hypothesize that the antiviral properties of these microRNAs are based on down-regulating specific cellular proteins that different viruses rely on. A broad, long-term goal in this work is to better understand how the microRNA mechanism (subtle down regulation of multiple host proteins simultaneously) could be used to treat infection. The advantage of this type of host-targeted therapy is that it could potentially be used to treat a range of infections and reduce the likelihood that viruses could readily mutate to become resistant. Here we implement cutting-edge biochemical techniques to identify the targets of antiviral microRNAs and determine how the targets suppress viral replication. Using murine and human cytomegalovirus as model systems, we examine targets of the miRNAs that are present in both mouse and human cells (and likely other animal hosts). In parallel, we examine whether cytomegaloviruses have evolved mechanisms for blocking host microRNA function. The end goal is to determine the mechanism of action of specific antiviral microRNAs and shed light on factors that will dictate the approaches required to use these molecules in a therapeutic context (e.g. combinatorial regulation of genes by multiple microRNAs and scope for viral interference and resistance).