BCCIP (BRCA2 and CDKN1A interacting protein) is a multifunctional tumor suppressor with roles spanning DNA repair, cell cycle regulation, and ribosome biogenesis. During interphase, BCCIP organizes and anchors microtubules at the centrosome, while during mitosis it stabilizes spindle pole organization, with isoform 2/alpha being particularly critical for spindle architecture and orientation 1. BCCIP enhances cell cycle arrest by potentiating CDKN1A-mediated CDK2 inhibition and functions as a BRCA2 cofactor in homologous recombination-mediated DNA repair 2. During replication stress, BCCIP recruits to stalled replication forks and prevents MRE11-mediated degradation of nascent DNA strands, protecting genomic stability 3. Additionally, BCCIP localizes to the nucleolus and is essential for 60S ribosome biogenesis by recruiting eIF6 and facilitating 12S pre-rRNA production 4. BCCIP expression is transcriptionally regulated by the INO80/YY1 chr10 remodeling complex in a feedback loop involving YY1 stability 56. Clinically, BCCIP downregulation occurs in 74-89% of ovarian cancer, renal cell carcinoma, and colorectal cancer samples and correlates with poor prognosis, tumor grade, and metastatic potential 27. BCCIP knockout causes embryonic lethality in mice, while partial loss triggers genomic instability and tumorigenesis 8.