Figure 6.

Exon1A IRES activity is inhibited by exons 1A_S and 1E. (A) Relative luciferase activities of CHO cells transfected with 300 ng of SL2 bicistronic constructs. Exons 1A, 1A_L or the 1A-1E combination were present immediately upstream of the Firefly-luciferase coding region. As a positive control for the IRES activity, an SL2-derived construct containing the viral EMCV element was used. The cx32 mutated 5′-UTR M2 was used as a negative control. (B) Structure of exon 1A_L as predicted by the mFOLD program. The calculated free energy (ΔG) is indicated. The AUG translation start site is pointed by an arrow. Sequence annealing to oligo A_S is labeled with a dotted line. (C) Relative luciferase activities of CHO cells transfected with 300 ng of SL2 bicistronic constructs containing either exon1A or exon1A_L. A thioate oligo annealing to 5–27 nt of the exon1A_L (oligo A_S) was either included (0.5 μM) (+) or excluded (−) in the transfection mixtures and the growing medium.