Myc TAD 1-103 region is sufficient for synergistic transcription activation with p300/CBP. (A) HeLa cells were transfected with pG5-E4-luciferase reporter and expression vectors for either Gal4 (lanes 1 and 2), Gal4-Myc(1-262) (lanes 3 and 4), Gal4-Myc(1-103) (lanes 5 and 6), or Gal4-Myc(41-143) (lanes 7 and 8) and with a p300 expression vector (+) or the corresponding empty vector (−). The activity of each Gal4 fusion activator in the presence of p300 (▪) is given as the percentage of its activity in the absence of p300, which was set arbitrarily to 100% (□, asterisks). (B) HeLa cells were transfected as described above but with (+) expression vectors for CBP, or CBPΔHAT or the corresponding empty vector (−), as indicated. The activity of each Gal4 fusion activator in the absence of CBP/CBPΔHAT was set to 100% as described above.