Fig. 3. Mechanisms of transcriptional activation by p300/CBP. (A) In the bridging model, p300/CBP proteins connect sequence-specific transcription factors to the transcription apparatus. (B) In the scaffold model, p300/CBP act as a protein scaffold for the assembly of multicomponent complexes that confer transcriptional activation. Examples of possible components, such as HAT (a co-factor containing acetyl-transferase activity), JMY and NAP, are indicated. (C) In the HAT model, either the intrinsic HAT activity of p300/CBP or HATs assembled in multicomponent complexes target chromatin and/or transcription factors to facilitate a transcriptional response.
