Bromodomain, polybromo repeat IV. Polybromo is a nuclear protein of unknown function, which contains 6 bromodomains. The human ortholog BAF180 is part of a SWI/SNF chromatin-remodeling complex, and it may carry out the functions of Yeast Rsc-1 and Rsc-2. It was shown that polybromo bromodomains bind to histone H3 at specific acetyl-lysine positions. Bromodomains are found in many chromatin-associated proteins and in nuclear histone acetyltransferases. They interact specifically with acetylated lysine, but not all the bromodomains in polybromo may bind to acetyl-lysine.