THE EPSTEIN-BARR-VIRUS NUCLEAR-PROTEIN-2 ACIDIC DOMAIN FORMS A COMPLEX WITH A NOVEL CELLULAR COACTIVATOR THAT CAN INTERACT WITH TFIIE

Epstein-Barr virus nuclear antigen 2 (EBNA 2) activates transcription of specific genes and is essential for B-lymphocyte transformation, EB NA 2 has an acidic activation domain which interacts with general tran scription factors TFIIB, TFIIH, and TAF40. We now show that EBNA 2 is specifically bound to a novel nuclear protein, p100, and that p100 can coactivate gene expression mediated by the EBNA 2 acidic domain. The EBNA 2 acidic domain was used to affinity purify p100. cDNA clones enc oding the p100 open reading frame were identified on the basis of pept ide sequences of the purified protein. Antibody against p100 coimmunop recipitated p100 and EBNA 2 from Epstein-Barr virus-transformed lympho cyte extracts, indicating that EBNA 2 and p100 are complexed in vivo. p100 overexpression in cells specifically augmented EBNA 2 acidic doma in-mediated activation. The coactivating effect is probably mediated b y p100 interaction with TFIIE. Bacterially expressed p100 specifically adsorbs TFIIE from nuclear extracts, and in vitro-translated p56 or p 34 TFIIE subunit can independently bind to p100, p100 also appears to be essential for normal cell growth, since cell viability was reduced by antisense p100 RNA and restored by sense p100 RNA expression.