Component of cullin-based E3 ubiquitin-protein ligase complexes which mediate the ubiquitination and subsequent proteasomal degradation of target proteins. The functional specificity of the E3 ubiquitin-protein ligase complex depends on the variable substrate recognition component. In association with ddb-1 directs ubiquitination of cdt-1 during S phase and is required for restraining DNA rereplication. Probably is involved in ubiquitination of cki-1. Protein modification; protein ubiquitination. Part of an E3 ubiquitin-protein ligase complex including cul-4 and ddb-1. Highest levels in embryos and lower levels in larvae and adults. Neddylated. Deneddylated via its interaction with the COP9 signalosome (CSN) complex. Belongs to the cullin family.