HCMV UL133/8 regulation of host cell signaling in viral latency and reactivation

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SUMMARY – PROJECT 1 The goal of our Program is to elucidate molecular mechanisms by which HCMV regulates host signaling in CD34+ hematopoietic progenitor cells (HPCs) for the establishment and maintenance of viral latency and reactivation from latency. HCMV remains a significant cause of morbidity and mortality after solid organ and hematopoietic stem cell transplantation despite advances in diagnostics and therapeutics. HCMV latency is complex and the signaling mechanisms for establishment and maintenance of HCMV latency, as well as for reactivation of virus are poorly understood. Our program has identified a number of viral proteins and miRNAs that regulate latency and reactivation by targeting host pathways. The complexity of signaling events and approaches to comprehensively address questions on viral latency and hematopoiesis can only be achieved through a collaborative effort. Using state-of-the art in vitro models in human CD34+ HPCs and in vivo models in humanized mice, our Program will address the individual and combined roles of viral factors modulating host signaling. Our Project (Project 1) will address the roles of the latency determinant UL138 in modulating host signaling pathways regulated through its interactions with ubiquitin specific protease (USP) complexes that regulate STAT1 and AKT signaling. We have defined interactions between UL138 and WDR48 and WDR20, which serve as a scaffold to activate USP1, USP12, and USP46. We hypothesize that UL138-host interactions with WDR/USP complexes coordinate signaling to regulate the switch between latency and reactivation. In Aim 1, we will determine how UL138 impacts WDR48/USP complexes and function. We will map the amino acids in UL138 that are required for interaction with WDR48/USP complexes and generate recombinant viruses defective for these interactions. In Aim 2, we will determine how UL138-WDR48/USP interactions impact latency and reactivation and the role of UL138 in activating STAT1 and AKT using recombinant viruses and knockdown of host factors. Aim 3 will expand our understanding of the regulation of STAT1 and AKT signaling by analyzing a greater network of regulators, proteins and miRNAs, that regulate STAT1 and AKT signaling to drive outcomes of infection in collaboration with Project 2 and Project 3. Collectively, our projects will provide the first comprehensive and mechanistic insights into the multi-faceted regulation of host signaling for the control of HCMV latency. The network of viral and host factors we have identified uniquely position us to define novel host and viral targets for antiviral strategies to control HCMV latency or reactivation. Our collaborative approach will provide unparalleled insights into the complex multi-factorial mechanisms regulating HCMV latency and reactivation.