AMF-1/Gps2 binds p300 and enhances its interaction with papillomavirus E2 proteins

The cellular protein AMF-1 (Gps2) positively modulates gene expression by t he papillomavirus E2 protein (D. E. Breiding et al,, Mel. Cell. Biol. 17:72 08-7219, 1997), We show here that AMF-1 also binds the transcriptional coac tivator p300 in vitro and in vivo. E2 interacted weakly with p300, These ob servations led to a model in which AMF-1 recruits p300 into a complex with E2, Cotransfection of AMF-1 or p300 stimulated levels of E2-dependent trans cription, while cotransfection of both AMF-1 and p300 showed an additive ef fect. The functional significance of p300 recruitment for E2 transactivatio n was evidenced by repression of E2-activated transcription by adenovirus E 1A, which inhibits both coactivator and acetylase activities of p300. Antib odies to AMF-1 or E2 immunoprecipitated histone acetylase activity from cel l lysates, Western blotting using antibody against acetyl-lysine failed to detect acetylation of AMF-1 or E2 in complex with p300, These results sugge st that AMF-1 facilitates the recruitment of p300 and its histone acetylase activity into complexes with E2 and represents a novel mechanism of transc riptional activation.