Epstein-Barr virus nuclear protein LP stimulates EBNA-2 acidic domain-mediated transcriptional activation.
Epstein-Barr virus (EBV) nuclear proteins EBNA-LP and EBNA-2 are the first two proteins expressed in latent infection of primary B lymphocytes. EBNA-2 is essential for lymphocyte transformation, and EBNA-LP is at least critical. While EBNA-2 activates specific viral and cellular promoters, EBNA-LP's role has been obscure. We now show that EBNA-LP stimulates EBNA-2 activation of the LMP1 promoter and of the LMP1/LMP2B bidirectional transcriptional regulatory element. EBNA-LP alone has only a negative effect. EBNA-LP also stimulates EBNA-2 activation of a multimerized regulatory element from the BamC EBNA promoter. Since both viral regulatory elements can bind the EBNA-2-associated cell protein RBPJ kappa, consensus RBPJ kappa binding sites were positioned upstream of the herpes simplex virus type 1 thymidine kinase promoter and were found to be sufficient for EBNA-LP and EBNA-2 coactivation. EBNA-LP strongly stimulated activation of an adenovirus E1b promoter with upstream Gal4 binding sites by a Gal4 DNA binding domain/ EBNA-2 acidic domain fusion protein, indicating that EBNA-LP coactivation requires only the EBNA-2 acidic domain to be localized near a promoter. The EBNA-LP stimulatory activity resides in the amino-terminal 66-amino-acid repeat domain. The carboxyl-terminal unique 45 amino acids appear to regulate EBNA-LP's effects. The first 11 amino acids of the 45 have a strong negative effect, while the last 10 are critical for the ability of the last 34 to relieve the negative effect. These results indicate that EBNA-LP's critical role in EBV-mediated cell growth transformation is in stimulating (and probably regulating) EBNA-2-mediated transcriptional activation.
Harada
S
S
Channing Laboratory, Department of Medicine, Brigham and Women's Hospital, Boston, Massachusetts, USA.
Kieff
E
E
D001665:Binding Sites; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D019309:Epstein-Barr Virus Nuclear Antigens / Q000235:genetics / Q000378:metabolism*; D015967:Gene Expression Regulation, Viral; D004854:Herpesvirus 4, Human / Q000235:genetics* / Q000378:metabolism; D006801:Humans; D051819:Immunoglobulin J Recombination Signal Sequence-Binding Protein; D009687:Nuclear Proteins; D012091:Repetitive Sequences, Nucleic Acid; D015533:Transcriptional Activation; D014162:Transfection; D014407:Tumor Cells, Cultured; D014763:Viral Matrix Proteins / Q000235:genetics*
D004268:DNA-Binding Proteins; C037662:EBV-associated membrane antigen, Epstein-Barr virus; D019309:Epstein-Barr Virus Nuclear Antigens; D051819:Immunoglobulin J Recombination Signal Sequence-Binding Protein; D009687:Nuclear Proteins; C497570:RBPJ protein, human; D014763:Viral Matrix Proteins