Discusses the isolation and characterization of a novel allele of the HRT1/RBX1 gene using a genetic screen for mutants unable to degrade Gic2p in Saccharomyces cerevisiae. Classes of E3 enzymes; Essential subunit of multiple skp1p-cullin-F-box (SCF) protein complexes; Role of ring-finger proteins in E3 ligases; Additional subunits of SCF complexes.