NEDD8 is a ubiquitin-like protein that controls vital bio-logical events through its conjugation to target proteins. Previously, we identifieda negative regulator oftheNEDD8 conjugation system, NEDD8 ultimate buster-1 (NUB1), that recruits NEDD8 and its conjugates to the proteasome for degradation. Recently, we performed yeast two-hybrid screening with NUB1 as bait and isolated a ubiquitin pre-cursor UbC1 that is composed ofnine tandem repeats of a ubiquitin unit through a-peptide bonds.
