Duality in bromodomain-containing protein complexes

Proteins that contain a motif called a bromodomain are implicated in both transcriptional activation and repression. The bromodomain of p/CAF, the only solution structure of a bromodomain that has been solved to date, reveals that the motif binds N-acetyl-lysine groups, presumably to anchor enzymatic functions to histones and by extension to chromatin. The enzymatic activities can either be encoded within the same polypeptide as the bromodomain motif, or associated with a multiprotein complex. Thus, a wide variety of chromatin-directed functions, including but not limited to phosphorylation, acetylation, methylation, transcriptional co-activation or recruitment, characterize the complexes that contain bromodomain motifs. Their versatility and ubiquity ensures diverse, rapid and flexible transcriptional responses.