FIG. 1.

TFIIB, 12S and 13S E1A proteins, and cyclin E-Cdk2 bind to similar regions of p300. (A) TFIIB binds to p300 carboxy-terminal fragments ending at amino acids 2414, 1906, and 1710. In vitro-translated, carboxy-terminal p300 fragments were incubated with GST (lanes 2, 5, 8, and 11) or GST-TFIIB (lanes 3, 6, 9, and 12). The in vitro-translated p300 fragments each began at amino acid 1240. Complexes were subjected to SDS–8% PAGE analysis, and 10% of the in vitro translation reaction mixture was loaded in lanes 1, 4, 7, and 10. (B) GST-12S and -13S E1A proteins bind to p300 carboxy-terminal fragments ending at amino acids 2414, 1906, and 1542. In vitro-translated, carboxy-terminal p300 fragments were incubated with a control GST (lanes 14, 18, 22, and 26), with GST-13S E1A (lanes 15, 19, 23, and 27), or with GST-12S E1A (lanes 16, 20, 24, and 28); this was followed by SDS–8% PAGE analysis. Lanes 13, 17, 21, and 25 contain 10% of each in vitro translation reaction product. (C) Immunoprecipitated Cdk2 complexes bind to p300 carboxy-terminal fragments ending at amino acids 2414, 1906, and 1542. Products of immunoprecipitations with control antibodies (lanes 30, 33, 36, and 39) or antibodies to Cdk2 (lanes 31, 34, 37, and 40) were incubated with in vitro-translated p300 fragments and subjected to SDS–8% PAGE analysis. Lanes 29, 32, 35, and 38 contain 10% of the in vitro-translated p300 fragments. Arrows labeled a, b, c, and d indicate the positions of carboxy-terminal p300 fragments ending at residues 2414, 1906, 1710, and 1542, respectively.