RCHY1 (ring finger and CHY zinc finger domain containing 1) is an E3 ubiquitin ligase with multiple cellular roles in protein degradation and quality control. Primary function: RCHY1 mediates ubiquitin-dependent degradation of target proteins including p53 and HDAC2 12. In melanophagy, RCHY1 functions as an essential E3 ligase required for selective autophagy-mediated degradation of melanosomes, working alongside autophagy receptor OPTN 3. Mechanism: RCHY1 contains a RING-finger domain enabling ubiquitin ligase activity 2. Its stability and activity are regulated by protein interactions—viral SARS proteases (PLpro and SUD) stabilize RCHY1 to promote p53 degradation and suppress antiviral immunity 14, while Hoxa2 transcription factor promotes RCHY1 proteasomal degradation independent of ubiquitin 56. Disease relevance: RCHY1 dysregulation impacts cancer pathogenesis; inverse RCHY1-HDAC2 correlation exists in tumors 2. PHB2-RCHY1 signaling promotes colon cancer proliferation, and targeting this pathway enhances drug cytotoxicity 7. RCHY1 additionally participates in ribosome-associated quality control targeting polyalanine-tailed substrates 8. Clinical significance: RCHY1 represents a therapeutic target for pigmentation disorders and cancer treatment strategies.