BRCA1–BARD1 complex (BRCA1–BARD1)

The **BRCA1–BARD1 complex** is a heterodimeric tumor suppressor that forms a specialized E3 ubiquitin ligase, essential for the repair of DNA double-strand breaks by homologous recombination. This complex is comprised of BRCA1 (breast cancer type 1 susceptibility protein) and BARD1 (BRCA1 associated RING domain protein 1), which dimerize primarily via their N-terminal RING (Really Interesting New Gene) domains[5][6]. BRCA1–BARD1 recognizes damaged chromatin and catalyzes the ubiquitylation of specific histone residues, particularly histone H2A and variant H2AX, thereby promoting recruitment and retention of DNA repair machinery at lesions[1][2][6]. The BRCA1–BARD1 interaction is also implicated in chromatin remodeling, cell cycle checkpoint control, and the regulation of transcription. Deficiency or mutation of either partner is strongly associated with hereditary breast and ovarian cancer as well as increased genomic instability[4][5]. Drugs such as PARP inhibitors exploit the loss of BRCA1–BARD1-mediated DNA repair (synthetic lethality) in cancer cells but do not directly target the interaction. Currently, there are no approved drugs that specifically disrupt or modulate the BRCA1–BARD1 interaction. The status of BRCA1 and BARD1 (mutational or expression) is a major biomarker in cancer risk assessment and therapy selection[4].

Other names

BRCA1/BARD1 complexBRCA1–BARD1 heterodimer

PARP inhibitors induce synthetic lethality in cells deficient in BRCA1–BARD1-mediated DNA repair. Modulation of homologous recombination repair by targeting upstream or downstream mediators that interact with BRCA1–BARD1.