Viral oncoproteins, such as adenoviral E1A and SV40 large T antigen, specifically target these proteins ( Arany et al., 1994 Arany et al., 1995 Eckner et al., 1994 Eckner et al., 1996a Whyte et al., 1989) (reviewed by Dyson and Harlow, 1992 Moran, 1993). They function as transcriptional co-activators and are involved in multiple, signal-dependent transcription events. The p300/CBP proteins, which include the distinct but related proteins p300 and CBP and potentially other proteins, such as p270, are a protein family that participate in many physiological processes, including proliferation, differentiation and apoptosis (reviewed by Janknecht and Hunter, 1996 Shikama et al., 1997 Giordano and Avantaggiati, 1999 Goodman and Smolik, 2000). With the current intense level of research activity, p300/CBP will continue to be in the limelight and, we can be confident, yield new and important information on fundamental processes involved in transcriptional control. Other proteins, including the p53 tumour suppressor, are targets for acetylation by p300/CBP. Another key property is the presence of histone acetyltransferase (HAT) activity, which endows p300/CBP with the capacity to influence chromatin activity by modulating nucleosomal histones. Providing a protein scaffold upon which to build a multicomponent transcriptional regulatory complex is likely to be an important feature of p300/CBP control. They act as protein bridges, thereby connecting different sequence-specific transcription factors to the transcription apparatus. The transcription regulating-properties of p300 and CBP appear to be exerted through multiple mechanisms.
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p300/CBP activity can be under aberrant control in human disease, particularly in cancer, which may inactivate a p300/CBP tumour-suppressor-like activity. P300/CBP transcriptional co-activator proteins play a central role in co-ordinating and integrating multiple signal-dependent events with the transcription apparatus, allowing the appropriate level of gene activity to occur in response to diverse physiological cues that influence, for example, proliferation, differentiation and apoptosis.