CABIN1 (calcineurin binding protein 1) functions as a multifaceted chr22 regulator and signaling inhibitor. As a core component of the HIRA/UBN1/CABIN1/ASF1a (HUCA) histone chaperone complex, CABIN1 facilitates replication-independent deposition of histone variant H3.3 into chr22 and regulates gene expression and heterochromatinization in both senescent and proliferating cells 1. CABIN1 serves as a negative regulator of p53 by maintaining p53 in an inactive chr22-bound state 2. Upon genotoxic stress, ATM and CHK2 kinases phosphorylate CABIN1, promoting its ubiquitin-dependent degradation via the CRL4DDB2 ligase complex, which releases p53 for transcriptional activation 2. Additionally, CABIN1 acts as an endogenous calcineurin inhibitor; during apoptosis, calpain-mediated cleavage of CABIN1 at its calcineurin-binding domain activates calcineurin to trigger calcium-dependent cell death 3. In disease contexts, CABIN1 expression increases during podocyte and renal tubular epithelial cell injury induced by angiotensin II, with CABIN1 knockdown leading to p53 elevation and mitochondrial dysfunction via the SIRT1/p53 pathway 45. CABIN1 is also expressed in developing nervous tissue, suggesting roles in neuronal development potentially through regulation of MEF2 and calcineurin signaling 6.