Fig. 4.

Role of eB in luciferase expression. Luciferase activity (expressed as the ratio of firefly to Renilla) measured after 36 h of transfection of NCI-H441 cells with experimental constructs containing eB within the heterologous SP-B and SP-D 5′UTRs, or the natural SP-A2 5′UTR sequence, in which eB was placed upstream (eBAD) or in between exons A and D (AeBD). Exon B increased luciferase activity in all cases (*P < 0.05 vs. constructs without eB), except when eB was placed inverted upstream of exons A and D (inveBAD), or replaced by a random sequence of the same length (ran). The AranD construct exhibited higher luciferase activity than AD (**P < 0.05), but lower than AeBD. The control construct without 5′UTR (LUC) exhibited the lowest translation compared with any other constructs shown in the figure (#P < 0.001). Luciferase activity was measured in triplicate for each sample. Each bar shows mean + SE (n = 3–6 independent experiments).