C/EBPɛ and c-myb cooperation is mediated by the carboxy-terminal half of C/EBPɛ. Expression plasmids for C/EBPɛ p32 (aa 1-281), C/EBPɛ p30 (aa 33-281), and two amino-terminal truncation mutants of C/EBPɛ (aa 118-281 and aa 218-281) (500 ng) were cotransfected with c-myb and NELuc reporter plasmid (4 μg) into CV-1 cells. Luciferase activity was assayed after 40 hours. The C/EBPɛ 118-281 mutant lacks the transactivation domain but still cooperates with c-myb.