Abstract
The BMRF1 protein of Epstein-Barr virus (EBV) has multiple roles in viral lytic infection, including serving as the DNA polymerase processivity factor, activating transcription from several EBV promoters and inhibiting the host DNA damage response to double-stranded DNA breaks (DSBs). Using affinity purification coupled to mass spectrometry, we identified the nucleosome remodeling and deacetylation (NuRD) complex as the top interactor of BMRF1. We further found that NuRD components localize with BMRF1 at viral replication compartments and that this interaction occurs through the BMRF1 C-terminal region previously shown to mediate transcriptional activation. We identified an RBBP4 binding motif within this region that can interact with both RBBP4 and MTA2 components of the NuRD complex and showed that point mutation of this motif abrogates NuRD binding as well as the ability of BMRF1 to activate transcription from the BDLF3 and BLLF1 EBV promoters. In addition to its role in transcriptional regulation, NuRD has been shown to contribute to DSB signaling in enabling recruitment of RNF168 ubiquitin ligase and subsequent ubiquitylation at the break. We showed that BMRF1 inhibited RNF168 recruitment and ubiquitylation at DSBs and that this inhibition was at least partly relieved by loss of the NuRD interaction. The results reveal a mechanism by which BMRF1 activates transcription and inhibits DSB signaling and a novel role for NuRD in transcriptional activation in EBV.IMPORTANCE The Epstein-Barr virus (EBV) BMRF1 protein is critical for EBV infection, playing key roles in viral genome replication, activation of EBV genes, and inhibition of host DNA damage responses (DDRs). Here we show that BMRF1 targets the cellular nucleosome remodeling and deacetylation (NuRD) complex, using a motif in the BMRF1 transcriptional activation sequence. Mutation of this motif disrupts the ability of BMRF1 to activate transcription and interfere with DDRs, showing the importance of the NuRD interaction for BMRF1 functions. BMRF1 was shown to act at the same step in the DDR as NuRD, suggesting that it interferes with NuRD function.
Keywords:
BMRF1; Epstein-Barr virus; NuRD; RNF168; double-stranded break signaling; transactivation.