Establishment of Oncogene-Induced Senescence by the Host DNA Damage Response After EBV Infection

Epstein-Barr virus (EBV) is an oncogenic gamma-herpesvirus that infects over 90% of adults worldwide. Typically, EBV establishes a benign latent infection that is controlled by a strong cytotoxic T cell immune response. However, EBV infection in immunocompromised patients has been associated with development of several lymphoid and epithelial cell malignancies, including Burkitt’s lymphoma, Hodgkin’s lymphoma, post-transplant lymphoproliferative disease, and nasopharyngeal carcinoma. In primary human B cells, EBV infection has been shown to induce a transient period of hyper-proliferation, but many of these infected cells succumb to a DNA damage response (DDR)-mediated growth arrest. We hypothesize that EBV infection triggers replicative stress early after infection and facilitates persistent activation of the DDR establishing oncogene-induced senescence. To test this hypothesis, we infected primary human B cells with EBV and examined cellular proliferation and host DNA damage response pathways at early and late stages post infection. We found that early after EBV infection, rapidly proliferating B cells exhibited signs of replication stress and reduced levels of purine dNTP nucleotide pools that are necessary for sustained proliferation. These findings suggest that purine dNTP biosynthesis plays a critical role in the early stages of EBV-mediated B cell immortalization. Furthermore, we observed the formation of persistent DDR foci in arrested B cells and identified key regulators of long-term outgrowth of EBV-infected B cells. Ultimately, this work has shown that early after EBV infection, cells that experience aberrant proliferation establish oncogene-induced senescence by chronically activating the DDR in the context of reduced dNTP nucleotide pools.