p300/CBP proteins: HATs for transcriptional bridges and scaffolds

p300/CBP transcriptional co-activator proteins play a central role in co-or dinating and integrating multiple signal-dependent events with the transcri ption apparatus, allowing the appropriate level of gene activity to occur i n response to diverse physiological cues that influence, for example, proli feration, differentiation and apoptosis. p300/CBP activity can be under abe rrant control in human disease, particularly in cancer, which may inactivat e a p300/CBP tumour-suppressor-like activity. The transcription regulating- properties of p300 and CBP appear to be exerted through multiple mechanisms . They act as protein bridges, thereby connecting different sequence-specif ic transcription factors to the transcription apparatus. Providing a protei n scaffold upon which to build a multicomponent transcriptional regulatory complex is likely to be an important feature of p300/CBP control. Another k ey property is the presence of histone acetyltransferase (HAT) activity, wh ich endows p300/CBP with the capacity to influence chromatin activity by mo dulating nucleosomal histones. Other proteins, including the p53 tumour sup pressor, are targets for acetylation by p300/CBP. With the current intense level of research activity, p300/CBP will continue to be in the limelight a nd, we can be confident, yield new and important information on fundamental processes involved in transcriptional control.