Fig. 3.

Exon B is a transcription enhancer. Luciferase mRNA levels (ratio of firefly to Renilla) were measured by real-time RT-PCR after 30 h of transfection with constructs containing the SP-A2 exon B in its natural (eB-SV40, eB-SV40-AD) or inverted (inveB-SV40, inveB-SV40-AD) orientation, upstream of the SV40 promoter and the AD 5′UTR. SV40-AeBD is used as positive control and SV40-LUC as a negative control. Transcription of luciferase was significantly higher in all cases regardless of eB orientation or position with respect to the promoter (*P < 0.05 vs. SV40-LUC; **,#P < 0.05 vs. all). Real-time RT-PCR was performed in triplicate for each sample. Each bar shows mean + SE (n = 3 independent experiments).