UBAC1 (UBA domain containing 1) serves as a non-catalytic adapter component of the KPC complex, an E3 ubiquitin-protein ligase. Within this complex, UBAC1 facilitates the transfer of polyubiquitinated target proteins to the 26S proteasome for degradation. The KPC complex catalyzes polyubiquitination of key cell-cycle regulators such as CDKN1B during G1 phase, and also promotes maturation of NFKB1 (the p105 precursor of NF-κB) through ubiquitin-mediated processing. Beyond canonical proteasomal pathways, UBAC1 participates in innate immune signaling by interacting with the CARMA2sh/CARD14 scaffold and TANK complex in human keratinocytes, where it negatively regulates NF-κB activation following Toll-like Receptor 3 stimulation 1. Recent studies suggest UBAC1 dysfunction may contribute to inflammatory conditions; the pathogenesis of psoriasis may involve altered UBAC1-mediated regulation of CARD14/CARMA2sh signaling 2, and UBAC1 has been identified as a potential causal gene in hypopituitarism, with serum metabolite-mediated mechanisms contributing to disease susceptibility 3. Additionally, lactate-induced post-translational modification of the KPC catalytic component RNF123 weakens its interaction with UBAC1, modulating NF-κB signaling and angiogenesis during wound healing 4. These findings position UBAC1 at a nexus of proteostasis, innate immunity, and metabolic regulation.