The Epstein-Barr virus nuclear protein 1 promoter active in type I latency is autoregulated.
The only member of the Epstein-Barr virus family of nuclear proteins (EBNAs) expressed during type I and type II latent infections is EBNA-1. This is in contrast to type III latency, during which all six nuclear proteins are expressed from a common transcription unit. The exclusive expression of EBNA-1 during type I and II latency is mediated through a recently identified promoter, Fp. The objective of this study was to characterize Fp in the Burkitt lymphoma cell background, where it is known to be differentially utilized. Using a short-term transfection assay and reporter gene plasmids containing Fp linked to the human growth hormone, we examined Fp activity in type I and type III latently infected and virus-negative Burkitt lymphoma cells. The data suggested that Fp is predominantly regulated through two distinct elements located between +24 and +270 relative to the transcription start site. One element positively mediates Fp activity, probably at the level of transcription, and acts in a virus-independent manner. The second element contains the EBNA-1 DNA binding domain III and negatively regulates Fp-directed gene expression in trans with EBNA-1 in type III as well as type I latency. Thus, we have identified a third function of EBNA-1, i.e., that of a repressor of gene expression, in addition to its known role in viral DNA replication and its ability to trans-activate gene expression. The overall activity of Fp in type I latently infected Burkitt cells was approximately sixfold lower than in virus-negative Burkitt cells, in which there is no autoregulation, suggesting that there is a fine balance between these two opposing regulatory elements during type I latency.
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Department of Virology and Molecular Biology, St. Jude Children's Research Hospital, Memphis, Tennessee 38101.
Henson
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EB
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D000956:Antigens, Viral / Q000235:genetics*; D002051:Burkitt Lymphoma; D002460:Cell Line; D004261:DNA Replication; D004279:DNA, Viral / Q000235:genetics / Q000302:isolation & purification; D019309:Epstein-Barr Virus Nuclear Antigens; D013006:Growth Hormone / Q000032:analysis / Q000235:genetics; D004854:Herpesvirus 4, Human / Q000235:genetics* / Q000276:immunology / Q000502:physiology; D006706:Homeostasis; D006801:Humans; D009687:Nuclear Proteins / Q000235:genetics; D010957:Plasmids; D011401:Promoter Regions, Genetic; D012326:RNA Splicing; D012333:RNA, Messenger / Q000235:genetics / Q000302:isolation & purification; D015183:Restriction Mapping; D014162:Transfection
D000956:Antigens, Viral; D004279:DNA, Viral; D019309:Epstein-Barr Virus Nuclear Antigens; D009687:Nuclear Proteins; D012333:RNA, Messenger; D013006:Growth Hormone