Functional interaction between nucleosome assembly proteins and p300/CREB-binding protein family coactivators.

The p300/CREB-binding protein (CBP) family of proteins consists of coactivators that influence the activity of a wide variety of transcription factors. Although the mechanisms that allow p300/CBP proteins to achieve transcriptional control are not clear, it is believed that the regulation of chromatin is an important aspect of the process. Here, we describe a new level of p300-dependent control mediated through the functional interaction between p300/CBP and members of the family of nucleosome assembly proteins (NAP), which includes NAP1, NAP2, and TAF1. We find that NAP proteins, which have previously been implicated in the regulation of transcription factor binding to chromatin, augment the activity of different p300 targets, including p53 and E2F, through a process that is likely to involve the physical interaction between p300 and NAP. NAP proteins can form oligomers, and the results show that NAP proteins can bind to both core histones and p300 coactivator proteins, perhaps in a multicomponent ternary complex. We also provide data in support of the idea that histones can influence the interaction between p300 and NAP protein. These results argue that NAP is a functionally important component of the p300 coactivator complex and suggest that NAP may serve as a point of integration between transcriptional coactivators and chromatin.