Effect of isoforms and a C-terminal mutation of C/EBPα on PSA promoter activity. LNCaP cells were transfected with PSA promoter/enhancer-driven luciferase reporter construct and expression vectors of C/EBPα expressing the wild type (WT) holoprotein, a mutated C/EBPα (D30) that gives rise to a protein identical to the p30 isoform of C/EBPα formed by an alternative initiation codon, and a C-terminal mutant (D4371) of C/EBPα formed by a 47 amino acid insertion at amino acid position 351. Luciferase activity was measured as in Figure 4. A. Schematic representations of the p42 and p30 isoform of C/EBPα and the C-terminal mutant protein (2). B. Expression of luciferase activity from the reporter construct after transfection with 100 ng of cDNA for C/EBPα p42 (wild type, WT), p30 isoform (D30), or C-terminal mutated cDNA (D4371) in LNCaP cells in the presence (dark bars) or absence (open bars) of DHT. The results expressed as relative light units are the means ± standard deviation of 3 separate experiments. Dark double stars signify statistical significance at p-value < 0.01 compared with control in DHT-stimulated transcription activity.