Ubiquitin-binding protein (PubMed:19722279). Required for the progression of DNA replication forks by targeting DNA replication licensing factor CDT1 for degradation (PubMed:26842564). Potentiates but cannot initiate FAS-induced apoptosis (By similarity). Interacts with CDT1 and ATPase VCP/p97 (PubMed:26842564). Interacts (via UBA domain) with FAS (via death domain) (PubMed:10462485). Interacts (via UBA domain) with NLRP12 (via DAPIN/PYRIN domain) (PubMed:21978668). Most abundant in testis, slightly less abundant in skeletal muscle and heart, followed by prostate, thymus, ovary, small intestine, and colon. Not detected in the peripheral blood leukocytes.