GABP cooperates with C/EBPα to strongly activate the FCAR promoter. (A,D) A schematic representation for the structure of the FCAR upstream-luciferase (Luc) constructs. The numbers indicate nucleotide positions relative to the translation initiation ATG at +1. The major transcription start site is indicated as bent arrow. X indicates mutated site. (B-C,E) HeLa cells were transfected with 0.7 μg indicated FCAR upstream-luciferase constructs in the absence or presence of 0.1 μg each of expression plasmids for GABPβ (pC3E4TF1-53S) and GABPα (pC3E4TF1-60S) or its deletion mutant, GABPαΔETS (pC3GAαΔETS) or GABPα318-454 (pC3GAα318-454), along with 3 ng C/EBPα expression plasmid (hCMV-C/EBPα) or the empty vector (pCMV-Empt) (B,E), or with 3 ng C/EBPβ expression plasmid (pD3NF-IL6) or the empty vector [pcDNA3.1(+)] (C); each sample was transfected with 5 ng pRL-CMV and the additional empty vector pCR3.1E to bring the amount of transfected DNA in each sample to 1 μg. Firefly and Renilla luciferase activities were determined 24 hours after transfection. Values are corrected for transfection efficiency and presented as the fold stimulation of each construct by the indicated transcription factor(s), compared with the promoter activity seen without the expression vector(s). Thin bars represent the standard errors (SE) from 3 to 6 transfections. ^*Significant decrease (P < .05) compared with pGLmCE12-259 by one-tailed t test.