Emerging tools to investigate bromodomain functions.

Bromodomains (BRDs) are evolutionarily conserved protein domains that specifically recognize acetylated lysine, a common epigenetic mark on histone tails. They are found in 61 human proteins, including enzymes, scaffolding platforms, and transcriptional co-activators. BRD-containing proteins play important roles in chromatin remodeling and the regulation of gene expression. Importantly, disruptions of BRD functions have been reported in various diseases. The premise of BRD-containing proteins as therapeutic targets has led to the development of multiple BRD inhibitors, many of which are currently being investigated in clinical trials. Thus, in the last decade significant efforts have been devoted to elucidating BRD biology. Here, we review the emerging tools that contributed to these efforts, from the structural definition of BRDs to their functional characterization. We further highlight the methods that have allowed the systematic screening of BRD targets and the identification of their endogenous interactors. Interactome mapping tools, such as affinity purification and proximity-based biotinylation, have contributed to the elucidation of BRD functions and their involvement in signaling pathways. We also discuss how recent progress in proteomics may further enhance our understanding of the biology of BRDs.