Termination of NF-κB activity through a gammaherpesvirus protein that assembles an EC5S ubiquitin-ligase

Open Access
Publisher Website
Google Scholar
Abstract
Host colonisation by lymphotropic gammaherpesviruses depends critically on the expansion of viral genomes in germinal centre (GC) B cells. Yet, host and virus molecular mechanisms involved in driving such proliferation remain largely unknown. Here, we show that the ORF73 protein encoded by the murid herpesvirus‐4 (MuHV‐4) inhibits host nuclear factor‐kappa B (NF‐κB) transcriptional activity through poly‐ubiquitination and subsequent proteasomal‐dependent nuclear degradation of the NF‐κB family member p65/RelA. The mechanism involves the assembly of an ElonginC/Cullin5/SOCS (suppressors of cytokine signalling)‐like complex, mediated by an unconventional viral SOCS‐box motif present in ORF73. Functional deletion of this SOCS‐box motif ablated NF‐κB inhibitory effect of ORF73, suppressed MuHV‐4 expansion in GC B cells and prevented MuHV‐4 persistent infection in mice. These findings demonstrate that viral inhibition of NF‐κB activity in latently infected GC centroblasts is critical for the establishment of a gammaherpesvirus persistent infection, underscoring the physiological importance of proteasomal degradation of RelA/NF‐κB as a regulatory mechanism of this signalling pathway.