Fig. 4.

Collaboration of T-bet with C/EBPβ in IFN-γ promoter transactivation. Jurkat T cells were cotransfected with pcDNA3-Tbet, pcDNA3-C/EBPβ, or pcDNA3-C/EBPβ mutant along with a constitutive β-galactosidase reporter. Shown are the results (mean ± SEM from three independent experiments) of transactivation assays using the indicated fusions of promoter sequences with a luciferase reporter, either without (A) or with (B) complete methylation of reporter plasmid DNA in vitro. The transactivation of promoter activity is presented as “fold induction” (normalized activity in transcription factor-transfected cells/empty vector controls, after normalizing to β-galactosidase activity programmed by a constitutive lacZ reporter construct). (C) Collaborative induction of the endogenous IFN-γ gene. T cells were transfected with the indicated combinations of T-bet (or its empty vector) along with empty vector, C/EBPβ, or the transactivation-defective C/EBPβ mutant as indicated. RT-PCR analyses of IFN-γ and GAPDH mRNAs were then performed within the linear range of amplification as in Fig. 1C. Shown is the result of one experiment representative of three with the same result.