Rescue of the Epstein-Barr virus BZLF1 mutant, Z(S186A), early gene activation defect by the BRLF1 gene product.
Expression of the Epstein-Barr virus (EBV) immediate-early protein, BZLF1 (Z), is sufficient to disrupt viral latency. Z transcriptionally activates the EBV early genes by binding to upstream Z-responsive elements (ZREs). Recently, a serine-to-alanine mutation of Z residue 186 (within the basic DNA binding domain) was shown to inhibit the ability of Z to induce lytic infection in latently infected cells, although the Z(S186A) mutant could still bind several known ZREs and activated an early EBV promoter (BMRF1) in transient reporter gene assays (Francis, A. L., Gradoville, L., and Miller, G. (1997). J. Virol. 71, 3054-3061). We now show that a specific deficiency in the ability to bind to ZRE elements in the immediate-early BRLF1 promoter may account for the inability of Z(S186A) to activate BRLF1 expression. Furthermore, we demonstrate that the ability of Z(S186A) to induce early BMRF1 and BHRF1 gene expression is rescued by cotransfection with a BRLF1 expression vector. However, the Z(S186A)/BRLF1 (R) combination cannot induce full lytic replication, suggesting that Z(S186A) may also be deficient in a replication-specific function. These results suggest that in the context of the intact viral genome, both Z and R expression are required for activation of early gene transcription in latently infected cells.
Adamson
A L
AL
Lineberger Comprehensive Cancer Center, Departments of Medicine and Microbiology, University of North Carolina at Chapel Hill, North Carolina, Chapel Hill, 27599-7295, USA.
Kenney
S C
SC
D000956:Antigens, Viral / Q000235:genetics; D001665:Binding Sites; D015153:Blotting, Western; D002051:Burkitt Lymphoma / Q000821:virology; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D015967:Gene Expression Regulation, Viral; D006367:HeLa Cells; D004854:Herpesvirus 4, Human / Q000235:genetics* / Q000378:metabolism; D006801:Humans; D017874:Immediate-Early Proteins / Q000378:metabolism*; D009154:Mutation; D011401:Promoter Regions, Genetic / Q000235:genetics; D020218:Response Elements / Q000235:genetics; D015534:Trans-Activators / Q000235:genetics* / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism*; D015533:Transcriptional Activation; D014162:Transfection; D014407:Tumor Cells, Cultured; D014764:Viral Proteins / Q000235:genetics; D017735:Virus Latency
D000956:Antigens, Viral; C083278:BHRF1 protein, Human herpesvirus 4; C068382:BRLF1 protein, Human herpesvirus 4; C063676:BZLF1 protein, Herpesvirus 4, Human; D004268:DNA-Binding Proteins; C083204:Epstein-Barr virus early antigen diffuse component; D017874:Immediate-Early Proteins; D015534:Trans-Activators; D014157:Transcription Factors; D014764:Viral Proteins