FIG. 3.

CBP HAT activity is necessary and sufficient for activation by Zta. (A) Immunoprecipitates derived from NIH 3T3 cells transfected with Flag-tagged full-length CBP (lanes 1 and 2), Flag-tagged CBP ΔHAT (lanes 3 and 4) or vector (lanes 5 and 6) were assayed for HAT activity with purified SONs in the absence (−) or presence (+) of Zta. (B) Western blot of immunoprecipitates derived from NIH 3T3 cells transfected with Flag CBP, Flag CBPΔHAT, or vector that were used for the HAT assay in panel A. (C) Ni-NTA-purified His-tagged CBP expressed and purified from baculovirus was assayed for acetylation of SONs in the absence (−) or presence (+) of Zta. CBP was increased by threefold increments up to 200 ng. Acetylated products were visualized by fluorography of SDS-PAGE gels.