TRERF1 (transcriptional regulating factor 1) is a nuclear DNA-binding transcription factor that plays a crucial role in steroid hormone regulation. TRERF1 activates transcription of CYP11A1, a key enzyme in steroid hormone synthesis, through direct DNA binding and synergistic interactions with coactivators CREBBP and EP300 1. The gene functions in both positive and negative regulation of RNA polymerase II-mediated transcription and participates in progesterone receptor signaling pathways. Clinically, TRERF1 has relevance across multiple disease contexts. Novel somatic mutations in TRERF1 (p.K1056Q and p.G1063R) have been identified in ovarian endometriosis patients, suggesting involvement in endometriosis pathogenesis through dysregulation of steroid hormone production 2. In breast cancer, TRERF1 was identified as a BCAR (breast cancer antiestrogen resistance) gene conferring tamoxifen resistance and estrogen independence; elevated TRERF1 expression associates with reduced metastasis-free survival in lymph node-negative breast cancer patients, independent of traditional prognostic factors 1 3. TRERF1 expression is upregulated in class-switched memory B cells, suggesting roles in adaptive immunity 4. Additionally, TRERF1 variants have been identified in intellectual disability cohorts 5 and obesity-associated bladder cancer 6, indicating broader pathogenic potential across diverse conditions.