Non-catalytic component of the KPC complex, a E3 ubiquitin-protein ligase complex that mediates polyubiquitination of target proteins, such as CDKN1B and NFKB1 (PubMed:15531880, PubMed:15746103, PubMed:16227581, PubMed:25860612). The KPC complex catalyzes polyubiquitination and proteasome-mediated degradation of CDKN1B during G1 phase of the cell cycle (PubMed:15531880, PubMed:15746103). The KPC complex also acts as a key regulator of the NF-kappa-B signaling by promoting maturation of the NFKB1 component of NF-kappa-B by catalyzing ubiquitination of the NFKB1 p105 precursor (PubMed:25860612). Within the KPC complex, UBAC1 acts as an adapter that promotes the transfer of target proteins that have been polyubiquitinated by RNF123/KPC1 to the 26S proteasome (PubMed:16227581).
