Deciphering the Role of Sumoylation During EBV Replication

Abstract

Epstein Barr Virus, a gamma herpes virus, is the known causative agent in infectious mononucleosis and is highly ubiquitous in nature. Although primary infection typically yields no long term issues, viral latency is associated with lymphomas and epithelial cell carcinomas. We documented that the presence of LMP1, the principal EBV oncogene, dysregulates cellular sumoylation processes in lymphoma tissues, modulates innate immune response, and maintains viral latency. Sumoylation is a dynamic process were target proteins are modified with free small ubiquitin like modifier (SUMO) proteins. The SUMO modification is vital for cellular processes including: immune response, DNA damage repair sensing, cell cycle progression, resistance to apoptosis, and metastasis. Several cancers display dysregulation of the sumoylation process, making the SUMO machinery a sufficient target for anti-cancer therapies. Known sumoylation inhibitors include natural extracts and antibiotics. However, many of these agents are nonspecific and/or demonstrate adverse effects like allergic reactions with botanical extracts. This piqued our interest in investigating synthetically engineered compounds along with a well-known natural extract inhibitor, Ginkgolic Acid (GA). ML-792, 2-D08, and TAK-981 are synthetically derived small molecule inhibitors that were identified as selective SUMO-inhibitors, interfering at different stages of the sumoylation process. We hypothesize that the SUMO-inhibitors will have therapeutic effects for the treatment of EBV-associated malignancies by modulating the EBV life-cycle. Results showed that each of the tested inhibitors decreased global levels of sumoylated proteins, though ML-792 and TAK-981 showed greater inhibition when compared to GA and 2-D08. Additionally, the SUMO-inhibitors induced low levels of spontaneous reactivation in latently infected B cells. We also confirm that sumoylation is important for maintaining EBV latency and lytic replication in B cells. Lastly, we note anti-viral potential for each tested inhibitor, particularly GA and 2-D08 have a better affect than ML-792 and TAK-981 in this regard. Of the tested sumoylation inhibitors, we now propose 2-D08 as the best potential therapeutic drug to aid the treatment of EBV-associated malignancies due to its ability to significantly reduce viral DNA levels following induced reactivation and decrease the ability of produced virus to infect additional cells.