Bromodomains are present in many chromatin-associated proteins such as the 
SWI/SNF and RSC chromatin remodelling and the SAGA HAT (histone 
acetyltransferase) complexes, and can bind to acetylated lysine residues in the 
N-terminal tails of the histones. Lysine acetylation is a histone modification 
that forms a stable epigenetic mark on chromatin for bromodomain-containing 
proteins to dock and in turn regulate gene expression. In order to better 
understand how bromodomains read the 'histone code' and interact with acetylated 
histones, we have tested the interactions of several bromodomains within 
transcriptional co-activators with differentially acetylated histone tail 
peptides and HAT-acetylated histones. Using GST (glutathione S-transferase) 
pull-down assays, we show specificity of binding of some bromodomains to 
differentially acetylated H3 and H4 peptides as well as HAT-acetylated histones. 
Our results reveal that the Swi2/Snf2 bromodomain interacts with various 
acetylated H3 and H4 peptides, whereas the Gcn5 bromodomain interacts only with 
acetylated H3 peptides and tetra-acetylated H4 peptides. Additionally we show 
that the Spt7 bromodomain interacts with acetylated H3 peptides weakly, but not 
with acetylated H4 peptides. Some bromodomains such as the Bdf1-2 do not 
interact with most of the acetylated peptides tested. Results of the peptide 
experiments are confirmed with tests of interactions between these bromodomains 
and HAT-acetylated histones. Furthermore, we demonstrate that the Swi2/Snf2 
bromodomain is important for the binding and the remodelling activity of the 
SWI/SNF complex on hyperacetylated nucleosomes. The selective recognition of the 
bromodomains observed in the present study accounts for the broad effects of 
bromodomain-containing proteins observed on binding to histones.