FUNCTIONAL INTERACTION OF A NOVEL CELLULAR PROTEIN WITH THE PAPILLOMAVIRUS E2 TRANSACTIVATION DOMAIN

The transactivation domain (AD) of bovine papillomavirus type 1 E2 sti mulates gene expression and DNA replication, To identify cellular prot eins that interact with this 215-amino-acid domain, we used a transact ivation-defective mutant as bait in the yeast two-hybrid screen, In vi tro and in vivo results demonstrate that the cDNA of one plasmid isola ted in this screen encodes a 37-kDa nuclear protein that specifically binds to an 82-amino-acid segment within the E2 AD. Mutants with point mutations within this E2 domain were isolated based on their inabilit y to interact with AMF-1 and were found to be unable to stimulate tran scription, These mutants also exhibited defects in viral DNA replicati on yet retained binding to the viral E1 replication initiator protein. Overexpression of AMF-1 stimulated transactivation by both wild-type E2 and a LexA fusion to the E2 AD, indicating that AMF-1 is a positive effector of the AD of E2. We conclude that interaction with AMF-1 is necessary for the transcriptional activation function of the E2 AD in mammalian cells.