Synonyms:2B28, LOC51035, SAKS1, SAPK substrate protein 1, UBA/UBX 33.3 kDa protein, UBX domain protein 1, UBXD10, UBXN1 Background:Ubiquitin-binding protein that interacts with the BRCA1-BARD1 heterodimer, and regulates its activity. Specifically binds 'Lys-6'-linked polyubiquitin chains. Interaction with autoubiquitinated BRCA1, leads to inhibit the E3 ubiquitin-protein ligase activity of the BRCA1-BARD1 heterodimer. Component of a complex required to couple deglycosylation and proteasome-mediated degradation of misfolded proteins in the endoplasmic reticulum that are retrotranslocated in the cytosol.