FANK1 (fibronectin type III and ankyrin repeat domains 1) is a nuclear protein that regulates apoptosis through activation of the AP-1 signaling pathway 12. The protein contains an N-terminal fibronectin type III domain and five C-terminal ankyrin repeats, showing high evolutionary conservation across vertebrate species 3. FANK1 functions as an anti-apoptotic protein by interacting with JAB1 (Jun activation domain-binding protein 1) to activate the AP-1 pathway, leading to upregulation and activation of c-Jun and its downstream target Bcl-3 2. The protein's stability is regulated through proteasomal degradation, with RYBP and phosphorylated YAF2 both inhibiting its degradation and prolonging its half-life 14. FANK1 is predominantly expressed in testis, specifically in mid to late pachytene spermatocytes and spermatids, suggesting a role in the transition from meiotic to haploid phases of spermatogenesis 3. In disease contexts, FANK1 has been identified as a signature gene in exhausted T cells during pancreatic cancer progression and shows genetic associations with palindromic rheumatism and intravenous immunoglobulin response in Kawasaki disease 567. The gene is subject to epigenetic regulation through rDNA cluster contacts that correspond to repressed chr10 states 8.