title: Multiple functions within the Epstein-Barr virus EBNA-3A protein.
abstract: Two regions of the EBNA-3A protein of Epstein-Barr virus were shown to be capable of binding to the cell protein RBP-Jk (also known as CBF-1), a component of the Notch signaling pathway. Consistent with this binding, EBNA-3A inhibited reporter gene expression from plasmids containing RBP-Jk DNA binding sites within their promoters, including the Cp promoter. When EBNA-3A was linked to a GAL4 DNA binding domain, it repressed the activity of a promoter containing GAL4 binding sites at all plasmid concentrations tested. However, a deletion mutant of EBNA-3A lacking amino acids 100 to 364 showed a biphasic response in the GAL4 assay: it inhibited transcription at low DNA concentrations but activated it at high DNA concentrations. There appears to be a gene activation function within EBNA-3A that is masked in the full-length protein in this assay. Current models for EBNA-3 function have stressed transcription repression through binding to RBP-Jk, but we consider an alternative scheme in which the role of the binding of EBNA-3A, -3B, and -3C to RBP-Jk is to buffer the levels of active EBNA-3 protein. We have also found that the behavior of EBNA-3A in a cell fractionation procedure that distinguishes insoluble matrix from soluble cell fractions is modified by EBNA-LP, indicating a further novel level of interplay between the EBNA proteins.
authors.affiliation: Ludwig Institute for Cancer Research, Imperial College School of Medicine at St. Mary's, London, United Kingdom.
authors.forename: I
authors.initials: I
authors.lastname: Cludts
authors.forename: P J
authors.initials: PJ
authors.lastname: Farrell
mesh_terms: D001665:Binding Sites; D002461:Cell Line, Transformed; D004268:DNA-Binding Proteins / Q000378:metabolism*; D019309:Epstein-Barr Virus Nuclear Antigens / Q000235:genetics / Q000378:metabolism*; D006367:HeLa Cells; D004854:Herpesvirus 4, Human / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D051819:Immunoglobulin J Recombination Signal Sequence-Binding Protein; D009687:Nuclear Proteins; D011401:Promoter Regions, Genetic; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism; D017384:Sequence Deletion; D014158:Transcription, Genetic; D014407:Tumor Cells, Cultured
chemical_list: D004268:DNA-Binding Proteins; D019309:Epstein-Barr Virus Nuclear Antigens; D051819:Immunoglobulin J Recombination Signal Sequence-Binding Protein; D009687:Nuclear Proteins; C497570:RBPJ protein, human; D012097:Repressor Proteins