UBAC1 (UBA domain containing 1) functions as a non-catalytic adapter component of the KPC E3 ubiquitin-ligase complex that regulates protein degradation and cellular signaling pathways. UBAC1 facilitates the transfer of polyubiquitinated target proteins from RNF123/KPC1 to the 26S proteasome for degradation 1. The protein plays critical roles in multiple cellular processes: it negatively regulates NF-κB signaling in human keratinocytes by participating in the CARMA2sh/TANK complex and promoting K63-linked ubiquitination of TANK following TLR3 activation 1. UBAC1 also contributes to wound healing through modulation of RNF123 lactylation, which affects NF-κB p105 processing and promotes angiogenesis 2. Additionally, UBAC1 has been implicated in cardiac protection, where KPC1 (RNF123) promotes proteasomal degradation of the pro-apoptotic protein BAX, reducing cardiomyocyte apoptosis during ischemia-reperfusion injury 3. Clinical significance includes potential associations with hypopituitarism susceptibility through metabolite-mediated pathways 4 and lung cancer prognosis in never smokers 5. The protein's dysfunction may contribute to inflammatory skin disorders and represents a potential therapeutic target for various diseases involving dysregulated protein degradation and inflammatory signaling.