PROJECT SUMMARY/ABSTRACT Epstein-Barr virus (EBV) is spread through saliva, infects oropharyngeal tissues including the tonsillar epithelium, and establishes life-long latency in the B-cell compartment in over 95% of the global adult human population. The oral transmission of EBV can result in infectious mononucleosis and can lead to several B-cell and epithelial cancers, including Burkitt lymphoma. This frequently presents as craniofacial and nasopharyngeal carcinomas. EBV uses both latent and lytic phases of its replication cycle to colonize the oropharynx and tonsils. Reactivation from latency is closely tied to EBV pathogenicity; however, the mechanisms that maintain latency and regulate reactivation in tonsillar memory B-cells and in EBV-associated diseases remain incompletely understood. Because EBV can evade immune detection while latent, most currently available therapies cannot harness the presence of the latent EBV genome. Developing a detailed understanding of the switch from latency to lytic reactivation may lay the foundation for lytic induction therapeutic strategies. One of the challenges to understanding the EBV lytic switch is to define the host factors necessary for maintaining EBV latency and how these factors are circumvented by EBV to allow reactivation. To begin to address this question, a human CRISPR/Cas9 screen was performed in Burkitt B-cells that were originally derived from a craniofacial biopsy. It showed that knockout of the human nuclear protein splicing factor proline and glutamine rich (SFPQ) strongly induces EBV lytic reactivation. SFPQ binds both DNA and RNA and is known to regulate both transcription and RNA splicing. Thus, SFPQ is poised as a master regulator of human and viral gene expression and viral genomic conformation during EBV latency. The goal of this study is to test the hypothesis that SFPQ suppresses EBV lytic reactivation in both DNA- and RNA- dependent manners and that EBV relieves this suppression by redistributing SFPQ to paraspeckles. Aim 1 is to determine the mechanism by which SFPQ represses EBV lytic reactivation. Aim 2 is to define the factors that mediate SFPQ subnuclear redistribution and function upon lytic reactivation. Molecular virology, transcriptomic, genomic, and microscopy approaches will be integrated to test this hypothesis. Understanding how SFPQ regulates the EBV and host genomes during latency and how SFPQ responds during lytic reactivation will contribute to a fundamental knowledge gap in how EBV subverts host factors to colonize oropharyngeal tissues and the B-cell compartment. This study may lay the foundation for lytic induction therapeutic strategies. The Brigham and Women’s Hospital at Harvard Medical School will provide an environment rich in both physical and intellectual resources for completion of this training. Furthermore, working with Dr. Gewurz in the collaborative atmosphere of his lab will enhance training in multi- disciplinary approaches to study EBV-host i...