p300 and CBP as transcriptional regulators and targets of oncogenic events

p300 and CBP are large nuclear proteins, encoded by two distinct genes, that appear to be involved in regulated transcription and cellular growth control. They are highly related in sequence and are expressed in most, if not all, mammalian cells. There is evidence for the existence of additional cellular proteins sharing at least some of the sequence motifs of p300 and CBP. Members of this protein family also appear to be present in Caenorhabditis elegans and Drosophila, but, based on the recently published complete genomic sequence, not in the yeast Saccharomyces cerevisiae. Thus, p300/ CBP-like proteins are likely confined to multicellular organisms where they may fulfill specific functions required for the proper growth and development. This view is supported by the occurrence of multiple developmental and proliferative defects in patients suffering from Rubinstein-Taybi syndrome which is due to an inactivating mutation in one CBP allele.