FIG. 5.

The c-Myc IRES is active during apoptosis. (A) HeLa cells were cotransfected (in triplicate) with pcDNA3.1/HisB/LacZ and either pGL3Rutr, pGL3RHRV, or pGL3R. Twenty-four hours after transfection, apoptosis was induced by the addition of 0.25 μg of TRAIL per ml, and samples were harvested at the time points indicated. (B) The expression of firefly luciferase generated from the IRES (by a cap-independent mechanism) was calculated relative to the expression of the upstream Renilla luciferase (cap-dependent expression), pGL3Rutr (closed circles), pGL3RHRV (closed squares), or pGL3R (closed triangles). (C) The expression of firefly luciferase generated from translation initiation of the IRES was also determined relative to that of the transfection control β-galactosidase, pGL3Rutr firefly luciferase (closed circles), pGL3RHRV firefly luciferase (closed squares), pGL3Rutr Renilla luciferase (open circles), and pGL3RHRV Renilla luciferase (open squares). All experiments were performed in triplicate on three independent occasions. SV40, simian virus 40; HRV, human rhinovirus.