Provided herein is a novel binding pocket within NEDD8 co-E3 proteins that binds NEDD8 E2 enzymes. Particularly at its M-Terminus. Methods are provided for screening for compounds that bind to the disclosed E2-binding pocket in NEDD8 co-E3 proteins. Compounds that bind to the E2-binding pocket and optionally inhibit the activity of NEDD8 co-E3 proteins and pharmaceutical compositions comprising the same are further provided. The NEDD8 co-E3 inhibitors find use, as agents preventing the NEDDylation of a target protein, in inhibiting cell growth and methods for treating cancers, inflammatory disorders, and pathogenic infections. The preferred inhibitors are peptides corresponding to a M-terminal fragment of Dnc1, e.g. MTLASKLKRDD, MLKLRQLQKKKQ, and MIKLFSLKQQKK, which are substituted at the M-Terminus with an uncharged group (e.g. acyl).