CCAR1 (Cell division cycle and apoptosis regulator 1) functions primarily as a multifaceted regulator of transcription, DNA repair, and RNA splicing. The protein serves as a transcriptional coactivator that associates with nuclear receptor complexes and mediates regulatory signals from upstream activators to basal transcription machinery 1. CCAR1 acts as a splicing fidelity factor with a critical role in DNA repair pathways, particularly the Fanconi anemia/BRCA pathway 23. Mechanistically, CCAR1 prevents inclusion of poison exons in FANCA mRNA through its EF hand domain, which interacts with the U2AF spliceosome heterodimer, thereby maintaining FANCA protein expression essential for interstrand crosslink repair 3. The protein exhibits context-dependent dual roles as either tumor promoter or suppressor, influenced by tissue type, mutation background, and protein-protein interactions 1. In hepatocellular carcinoma, exosomal circCCAR1 promotes CD8+ T-cell dysfunction and anti-PD1 therapy resistance 4. Clinically, CCAR1 serves as an autoantibody target in myositis patients, where anti-CCAR1 positivity may attenuate malignancy risk in anti-TIF1γ-positive cases 5. CCAR1 functional mimetics show promise as cancer therapeutics by promoting p53-independent apoptosis 6.