THE TRANSCRIPTIONAL COACTIVATORS P300 AND CBP ARE HISTONE ACETYLTRANSFERASES

p300/CBP is a transcriptional adaptor that integrates signals from man y sequence-specific activators via direct interactions. Various cellul ar and viral factors target p300/CBP to modulate transcription and/or cell cycle progression. One such factor, the cellular p300/CBP associa ted factor (PCAF), possesses intrinsic histone acetyltransferase activ ity. Here, we demonstrate that p300/CBP is not only a transcriptional adaptor but also a histone acetyltransferase. p300/CBP represents a no vel class of acetyltransferases in that it does not have the conserved motif found among various other acetyltransferases. p300/CBP acetylat es all four core histones in nucleosomes. These observations suggest t hat p300/CBP acetylates nucleosomes in concert with PCAF.