title: The B-cell-specific transcription factor and master regulator Pax5 promotes Epstein-Barr virus latency by negatively regulating the viral immediate early protein BZLF1.
abstract: The latent-to-lytic switch of Epstein-Barr virus (EBV) is mediated by the immediate early protein BZLF1 (Z). However, the cellular factors regulating this process remain incompletely characterized. In this report, we show that the B-cell-specific transcription factor Pax5 helps to promote viral latency in B cells by blocking Z function. Although Z was previously shown to directly interact with Pax5 and inhibit its activity, the effect of Pax5 on Z function has not been investigated. Here, we demonstrate that Pax5 inhibits Z-mediated lytic viral gene expression and the release of infectious viral particles in latently infected epithelial cell lines. Conversely, we found that shRNA-mediated knockdown of endogenous Pax5 in a Burkitt lymphoma B-cell line leads to viral reactivation. Furthermore, we show that Pax5 reduces Z activation of early lytic viral promoters in reporter gene assays and inhibits Z binding to lytic viral promoters in vivo. We confirm that Pax5 and Z directly interact and show that this interaction requires the carboxy-terminal DNA-binding/dimerization domain of Z and the amino-terminal DNA-binding domain of Pax5. A Pax5 DNA-binding mutant (V26G/P80R) that interacts with Z retains the ability to inhibit Z function, whereas a Pax5 mutant (Δ106-110) that is deficient for interaction with Z does not inhibit Z-mediated lytic viral reactivation. Since the B-cell-specific transcription factor Oct-2 also directly interacts with Z and inhibits its function, these results suggest that EBV uses multiple redundant mechanisms to establish and maintain viral latency in B cells.
authors.affiliation: Department of Oncology (McArdle Laboratory for Cancer Research), University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin, USA.
authors.forename: Ryan M
authors.initials: RM
authors.lastname: Raver
authors.forename: Amanda R
authors.initials: AR
authors.lastname: Panfil
authors.forename: Stacy R
authors.initials: SR
authors.lastname: Hagemeier
authors.forename: Shannon C
authors.initials: SC
authors.lastname: Kenney
mesh_terms: D015153:Blotting, Western; D045744:Cell Line, Tumor; D047369:Chromatin Immunoprecipitation; D017931:DNA Primers / Q000235:genetics; D024202:Electrophoretic Mobility Shift Assay; D015967:Gene Expression Regulation, Viral / Q000502:physiology*; D005822:Genetic Vectors / Q000235:genetics; D004854:Herpesvirus 4, Human / Q000502:physiology*; D006801:Humans; D016086:Lentivirus; D051757:PAX5 Transcription Factor / Q000378:metabolism*; D010957:Plasmids / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015534:Trans-Activators / Q000378:metabolism*; D017735:Virus Latency / Q000502:physiology*
chemical_list: C063676:BZLF1 protein, Herpesvirus 4, Human; D017931:DNA Primers; D051757:PAX5 Transcription Factor; C497281:PAX5 protein, human; D015534:Trans-Activators