Other E2F family members can bind and activate Trib2 promoter. (A) 3T3 cells were cotransfected with E2F1, E2F2, E2F3, E2F4, E2F5, or pcDNA empty expression vector and Trib2 luciferase reporter plasmids (pGL3 basic control or 2.6-kb promoter region), and luciferase activity was measured. Data presented are mean ± SD of duplicate cultures and representative of 3 independent experiments. *P < .05 and ***P < .001. (B) K562 cells were chromatin immunoprecipitated using anti-E2F1, anti-E2F2, anti-E2F3, anti-E2F4, anti-E2F5, antiacetylated histone 4 (Ac-His4), or normal IgG control antibodies. PCR was performed using primers directed against the E2F binding region containing sites B and C and using primers against a −5-kb region as a negative control. Graphs represent fold enrichment of DNA compared with the IgG control and are representative of 3 independent experiments, and error bars denote ± SD of each sample. *P < .05, **P < .005, and ***P < .001.