Bromodomain - containing protein 4 （BRD4） is a pivotal protein in epigenetic regulation. As a member of the BET （bromodomain and extra - terminal domain） family, it binds to acetylated lysine residues on histone tails via its bromodomains. This binding enables BRD4 to recruit transcriptional co - activators, such as the positive transcription elongation factor b （P - TEFb）, and facilitate the transition from transcription initiation to elongation. In normal cells, BRD4 is involved in cell cycle progression, differentiation, and development. However, in cancer, aberrant BRD4 function is frequently observed. It drives the over - expression of oncogenes, fueling tumor cell growth, proliferation, and survival.