ABSTRACT It is our ultimate goal to define the molecular basis for EBV-mediated metabolic control critical for B-cell tumorigenesis. In this proposal, we will focus on how EBV promotes the balanced upregulation of oxidative phosphorylation (OXPHOS) and glycolysis supporting B-cell immortalization and tumorigenesis. It is our central hypothesis that the viral latent transcription factor, EBNA-LP, functions as a mimic of the OXPHOS transcriptional co-activator PGC-1 while glycolysis and redox balance are maintained through viral upregulation of the lactate transporters MCT1 and 4. We have formulated our central hypothesis based on preliminary data including orthogonal approaches that define interactions between EBNA-LP and OXPHOS transcription factors, define a new post-translational modification on EBNA-LP, and characterize the metabolic consequences of suppressing viral-mediated lactate export. We found that the viral EBNA-LP protein associates with NRF-1, ERR, and YY- 1 mimicking the cellular co-activator PGC-1. We describe a novel post-translational modification of EBNA-LP, hydroxyprolination, that we propose is critical for higher order complex formation enabling transcriptional activation. Balanced with an increase in OXPHOS promoted by EBNA-LP, the upregulation of glycolytic enzymes by EBNA2 and c-MYC leads to an accumulation of lactate in cells that must be exported to sustain B-cell proliferation. We found that cellular monocarboxylate transporters, MCT1 and MCT4, are temporally regulated by EBV to sustain B-cell proliferation through maintaining NAD+/NADH ratios and glutathione levels to counter the accumulation of reactive oxygen species. Therefore, the rationale for this proposed research is that understanding how EBV regulates cellular metabolism during B-cell immortalization could reveal novel therapeutic modalities to target EBV-infected B-cell lymphomas. We plan to test our central hypothesis and complete the objectives in this proposal through the following two specific aims: i) to determine the molecular mechanism by which EBNA-LP coordinates EBV-regulated oxidative phosphorylation to immortalize naïve B cells and ii) to define the viral-mediated mechanism for temporal regulation of the monocarboxylate transporters, MCT1 and 4, through B-cell outgrowth and the consequences of their antagonism.