Constitutively active Cullin-RING-Ligases fail to rescue loss of NEDD8 conjugation in Schizosaccharomyces pombe.

In fission yeast, the only known essential function of Ned8p is the modification of the cullin, Pcu1p, and subsequent Cullin-RING-Ligase (CRL) activation and substrate ubiquitination. We show here that a functional Pcu1p mutant, deleted for its C-terminal autoinhibitory domain, which negates the requirement of neddylation for ligase activity, is unable to rescue the loss of neddylation. These findings suggest that the neddylation of non-cullin substrate(s) are required for Schizosaccharomyces pombe viability.