The human gammaherpesviruses Epstein-Barr virus and Kaposi's sarcoma-associated herpesvirus are etiologic agents of numerous B cell lymphomas. A hallmark of gammaherpesvirus infection is their ability to establish lifelong latency in B cells. However, the specific mechanisms that mediate chronic infection in B cells in vivo remain elusive. Cellular E3 ubiquitin ligases regulate numerous biological processes by catalyzing ubiquitylation and modifying protein location, function, or half-life. Many viruses hijack host ubiquitin ligases to evade antiviral host defense and promote viral fitness. Here, we used the murine gammaherpesvirus 68 in vivo system to demonstrate that the E3 ligase Cul4b is essential for this virus to establish latency in germinal center B cells. These findings highlight an essential role for this E3 ligase in promoting chronic gammaherpesvirus infection in vivo and suggest that targeted inhibition of E3 ligases may provide a novel and effective intervention strategy against gammaherpesvirus-associated diseases.Keywords: B cell; Cullin 4b (Cul4b); E3 ligase; gammaherpesvirus; germinal center; herpesvirus; latency; murine gammaherpesvirus 68 (MHV68).