Contribution of C/EBP proteins to Epstein-Barr virus lytic gene expression and replication in epithelial cells.
The contribution of C/EBP proteins to Epstein-Barr virus (EBV) lytic gene expression and replication in epithelial cells was examined. Nasopharyngeal carcinoma cell lines constitutively expressed C/EBPbeta and had limited C/EBPalpha expression, while the AGS gastric cancer cell line expressed significant levels of both C/EBPalpha and C/EBPbeta. Induction of the lytic cycle in EBV-positive AGS/BX1 cells with phorbol ester and sodium butyrate treatment led to a transient stimulation of C/EBPbeta expression and a prolonged increase in C/EBPalpha expression. In AGS/BX1 cells, endogenous C/EBPalpha and C/EBPbeta proteins were detected associated with the ZTA and oriLyt promoters but not the RTA promoter. Electrophoretic mobility shift assays confirmed binding of C/EBP proteins to multiple sites in the ZTA and oriLyt promoters. The response of these promoters in reporter assays to transfected C/EBPalpha and C/EBPbeta proteins was consistent with the promoter binding assays and emphasized the relative importance of C/EBPs for activation of the ZTA promoter. Mutation of the oriLyt promoter proximal C/EBP site had little effect on ZTA activation of the promoter in a reporter assay. However, this mutation impaired oriLyt DNA replication, suggesting a separate replication-specific contribution for C/EBP proteins. Finally, the overall importance of C/EBP proteins for lytic gene expression was demonstrated using CHOP10 to antagonize C/EBP DNA binding activity. Introduction of CHOP10 significantly impaired induction of the ZTA, RTA, and BMRF1 proteins in chemically treated AGS/BX1 cells. Thus, C/EBPbeta and C/EBPalpha expression are associated with lytic induction in AGS cells, and expression of C/EBP proteins in epithelial cells may contribute to the tendency of these cells to exhibit constitutive low-level ZTA promoter activity.
Huang
Jian
J
Johns Hopkins School of Medicine, Bunting-Blaustein Building CRB308, 1650 Orleans Street, Baltimore, MD 21231-1000, USA.
Liao
Gangling
G
Chen
Honglin
H
Wu
Frederick Y
FY
Hutt-Fletcher
Lindsey
L
Hayward
Gary S
GS
Hayward
S Diane
SD
D000956:Antigens, Viral / Q000096:biosynthesis / Q000235:genetics; D001483:Base Sequence; D022762:CCAAT-Enhancer-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D045744:Cell Line, Tumor; D004279:DNA, Viral / Q000235:genetics; D004268:DNA-Binding Proteins / Q000096:biosynthesis / Q000235:genetics; D004847:Epithelial Cells / Q000378:metabolism / Q000821:virology; D015870:Gene Expression; D005814:Genes, Viral; D006367:HeLa Cells; D004854:Herpesvirus 4, Human / Q000235:genetics* / Q000502:physiology*; D006801:Humans; D017874:Immediate-Early Proteins / Q000096:biosynthesis / Q000235:genetics; D011401:Promoter Regions, Genetic; D015534:Trans-Activators / Q000096:biosynthesis / Q000235:genetics; D014764:Viral Proteins / Q000096:biosynthesis / Q000235:genetics; D014779:Virus Replication
D000956:Antigens, Viral; C068382:BRLF1 protein, Human herpesvirus 4; C063676:BZLF1 protein, Herpesvirus 4, Human; D022762:CCAAT-Enhancer-Binding Proteins; D004279:DNA, Viral; D004268:DNA-Binding Proteins; C083204:Epstein-Barr virus early antigen diffuse component; D017874:Immediate-Early Proteins; D015534:Trans-Activators; D014764:Viral Proteins