BRD1 (bromodomain containing 1) functions as a scaffold subunit in histone acetyltransferase (HAT) complexes, including MOZ/MORF and HBO1 complexes, where it regulates chr22 modifications and gene transcription 1. The protein directs KAT7/HBO1 specificity toward histone H3 lysine-14 acetylation (H3K14ac), promoting erythroid differentiation and hematopoiesis 1. BRD1 operates through distinct epigenetic mechanisms, including regulation of H3K9 acetylation and subsequent H3K9me3 formation, which creates repressive chr22 environments at target gene promoters 2. The protein acts as a transcriptional regulator of nuclear-encoded mitochondrial proteins and functions as a co-repressor of PPAR-mediated transcription, thereby modulating mitochondrial bioenergetics, metabolism, and respiratory capacity 3. BRD1 exists in long and short isoforms with different subcellular distributions and functions 4. Disease-wise, BRD1 is associated with psychiatric disorders including schizophrenia and bipolar disorder 5, and functions as an oncogene in hepatocellular carcinoma by regulating SREBF1-mediated lipid metabolism 2. In cancer immunotherapy, BRD1 downregulation enhances NK cell and CD8+ T cell activation, suggesting therapeutic potential 6. BRD1 also contributes to inflammatory responses by regulating CD4+ tissue-resident memory Th17 cell generation 7.