RCOR1 (REST corepressor 1) functions as an essential component of transcriptional repressor complexes that regulate gene expression through chr14 modification. RCOR1 serves as a core component of the BHC (BRAF-HDAC complex) and CoREST complexes, which repress transcription of neuron-specific genes in non-neuronal cells by recruiting histone-modifying enzymes 1. The protein plays a central role in promoting KDM1A (LSD1) demethylase activity on histone H3 lysine 4, while simultaneously protecting LSD1 from proteasomal degradation 2. RCOR1 also participates in RCOR/GFI/KDM1A/HDAC complexes that control hematopoietic differentiation by suppressing genes involved in blood cell development 2. Disease relevance includes involvement in cancer progression, where RCOR1 expression is altered in various malignancies. In osteoarthritis, reduced RCOR1 levels contribute to increased expression of cartilage-degrading enzymes MMP13 and ADAMTS5 through upregulation of HES1 3. In gliomas, RCOR1 expression correlates with REST-mediated repression of neuronal genes like SYN1 4. RCOR1 also plays a role in viral latency, as part of LSD1-CoREST complexes that maintain Epstein-Barr virus dormancy 5. Clinically, targeting RCOR1-containing complexes shows therapeutic promise, with dual HDAC/LSD1 inhibitors demonstrating anti-cancer effects 6.