PU box-binding transcription factors and a POU domain protein cooperate in the Epstein-Barr virus (EBV) nuclear antigen 2-induced transactivation of the EBV latent membrane protein 1 promoter.
Expression of the Epstein-Barr virus (EBV) latent membrane protein (LMP1) is regulated by virus- and host cell-specific factors. The EBV nuclear antigen 2 (EBNA2) has been shown to transactivate a number of viral and cellular gene promoters including the promoter for the LMP1 gene. EBNA2 is targeted to at least some of these promoters by interacting with a cellular DNA binding protein, RBP-J kappa. In the present report we confirm and extend our previous observation that the LMP1 promoter can be activated by EBNA2 in the absence of the RBP-J kappa-binding sequence in the LMP1 promoter regulatory region (LRS). We show that two distinct LRS regions, -106 to +40 and -176 to -136, contribute to EBNA2 responsiveness. Site-directed mutagenesis analysis of the upstream -176/-136 EBNA2 responsive element revealed that two critical cis-acting elements are required for full promoter function. These same elements analysed by electrophoretic mobility shift assays define two binding sites recognized by nuclear factors derived from B cells. An octamer-like sequence (-147 to -139) contained overlapping binding sites for an unidentified transcriptional repressor on the one hand and a factor(s) belonging to the POU domain family but distinct from Oct-1 and Oct-2 on the other. An adjacent purine tract (-171 to -155) held a PU.1 binding site, which was also recognized by a related factor. The results suggest that the POU domain protein and either of two PU box-binding factors bind simultaneously to LRS, creating a ternary complex that might be in part responsible for mediating the transactivation of the LMP1 promoter by EBNA2. There were no qualitative differences between EBV-negative and EBV-positive cells with regard to transcription factor binding to the octamer-like sequence and the PU.1 recognition site, as revealed by electrophoretic mobility shift assays.
Sjöblom
A
A
Department of Clinical Chemistry and Transfusion Medicine, Sahlgrenska University Hospital, Gothenburg, Sweden.
Jansson
A
A
Yang
W
W
Laín
S
S
Nilsson
T
T
Rymo
L
L
D000956:Antigens, Viral / Q000378:metabolism*; D001483:Base Sequence; D001665:Binding Sites; D002461:Cell Line, Transformed; D004268:DNA-Binding Proteins / Q000378:metabolism*; D019309:Epstein-Barr Virus Nuclear Antigens; D006801:Humans; D051819:Immunoglobulin J Recombination Signal Sequence-Binding Protein; D050835:Interferon Regulatory Factors; D008969:Molecular Sequence Data; D009687:Nuclear Proteins; D009838:Oligodeoxyribonucleotides; D050809:POU Domain Factors; D011401:Promoter Regions, Genetic; D012045:Regulatory Sequences, Nucleic Acid; D015534:Trans-Activators / Q000378:metabolism*; D014157:Transcription Factors / Q000378:metabolism*; D015533:Transcriptional Activation; D014763:Viral Matrix Proteins / Q000235:genetics*; D000099218:Interferon Regulatory Factor-4
D000956:Antigens, Viral; D004268:DNA-Binding Proteins; D019309:Epstein-Barr Virus Nuclear Antigens; D051819:Immunoglobulin J Recombination Signal Sequence-Binding Protein; D050835:Interferon Regulatory Factors; D009687:Nuclear Proteins; D009838:Oligodeoxyribonucleotides; D050809:POU Domain Factors; D015534:Trans-Activators; D014157:Transcription Factors; D014763:Viral Matrix Proteins; D000099218:Interferon Regulatory Factor-4; C037662:EBV-associated membrane antigen, Epstein-Barr virus; C497570:RBPJ protein, human