Bromodomain-containing protein 4 (BRD4) contains 2 bromo-domains. Bromo-domains are found in chromatin-associating proteins and can interact specifically with acetylated lysine. BRD4 is described as a chromatin adaptor and has been shown to bind acetylated chromatin. It was originally identified as MCAP (mitotic chromosome associated protein) due to its association with mitotic chromosomes. BRD4 also associates with several transcription complexes such as the Mediator complexes and P-TEFb complexes and is considered to function as a transcriptional co-factor.