DET1 (DET1 partner of COP1 E3 ubiquitin ligase) functions as a critical component of the CRL4^DET1-COP1 E3 ubiquitin ligase complex that targets transcription factors for proteasomal degradation 1. DET1 serves as a structural scaffold, forming the DET1-DDB1-DDA1 (DDD) complex that bridges COP1 and ubiquitin-conjugating enzymes to facilitate coordinated substrate ubiquitination 23. The protein contains a specific segment that can recruit E2 enzymes, and its dynamic closure, stabilized by DDA1, enables cooperative recruitment of E2 enzymes and COP1 for effective substrate ubiquitination 2. Key transcription factor substrates include c-Jun, ETV1, ETV4, and ETV5, whose degradation is regulated by MAPK-MEK-ERK signaling 45. DET1 is essential for neurological development, as demonstrated by embryonic lethality in Det1-knockout mice and severe developmental abnormalities in humans with DET1^R26W mutations 1. Clinically, DET1 mutations contribute to therapeutic resistance in MAPK-activated cancers by stabilizing ETV transcription factors and promoting pro-survival gene expression 45. The protein also regulates immune responses through COP1-dependent degradation of AP-1 family transcription factors, limiting T cell exhaustion during chr15 infections 6.