Mapping the protein domains of androgen receptor (AR) and CCAAT enhancer binding protein-α (C/EBPα) required for their interaction in the context of DNA-bound C/EBPα. (a) HeLa cells were transfected with GAL4-C/EBPα or Gal4 expression plasmid together with an expression plasmid for either VP16 or VP16 fusion proteins with the full-length AR (VP16-AR), AR with its N-terminal amino acids 1–37 deleted (VP16-delAR(N)), the AB domains of AR (VP16-AB), the CD domains of AR (VP16-CD), the E domain of AR (VP16-E) or the CDE domains of AR (VP16-CDE). The cells were co-transfected with the Gal4-TATA-Luc reporter. At 48h after transfection, the cells were harvested to measure luciferase activity. (b) HeLa cells were transfected with an expression plasmid for either Gal4, the Gal4 fusion protein GAL4-C/EBPα(2–217) or GAL4 fusion proteins with various portions of C/EBPα polypeptide, as illustrated in the figure. The cells were co-transfected with the AR expression plasmid or vector control together with the Gal4-TATA-Luc promoter construct. The cells were treated with testosterone (10 nM) for the duration of the transfection (48 h) after which they were harvested for luciferase assays. The values are plotted as the fold increase in promoter activity relative to the values in the absence of AR. The western blot shows the relative expression levels of the fusion proteins by probing with antibody to GAL4. (c) HeLa cells were transfected with expression plasmids for C/EBPα or its mutant forms containing either an internal deletion of amino acids 146–156 or mutation of R154 to A. The cells were co-transfected with the AR expression plasmid or vector control together with the (C/EBP)3-TATA-Luc promoter construct. The cells were treated with testosterone (10 nM) for the duration of the transfection (48h) after which they were harvested for luciferase assays. The western blot shows the relative expression levels by probing with antibody to C/EBPα. For panels a–c, the P-values for the differences noted in the text were <0.001.