Table 3. The effects of picornaviral proteases on mRNA translation efficiency in poly(A)-dependent RRL and non-permissive mammalian cell lines.
| Translation efficiency (%) | IRES/mRNA | ||||||
|---|---|---|---|---|---|---|---|
| PV | HRV | HAV | EMCV | FMDV | HCV | Op24f | |
| In permissive cellsa | 43 (± 5) | 26 (± 14) | 5 (± 2) | 84 (± 12) | 90 (± 8) | 70 (± 13) | nd |
| In non-permissive cellsb | 4 (± 5) | 1 (± 1.4) | 0.1 (± 0.2) | 39 (± 19) | 92 (± 11) | 88 (± 9) | nd |
| In Neuro-2A cells – proteasec | 5 | 2.4 | 0.1 | 56 | 100 | 82 | nd |
| In Neuro-2A cells + proteasec | 45 (12) | 52 (16) | 0.2 (1.3) | 84 (1.6) | 100 (1.3) | 67 (0.9) | nd |
| In depleted RRL and physiological saltd | 0.6 | 0.2 | 0.03 | 28 | 91 | 91 | 33 |
| In depleted RRL and physiological salte + protease | 4.2 (7) | 0.9 (4) | 0.03 (1.0) | 71 (2.5) | 100 (1.1) | 85 (1.0) | 1.7 (0.05) |
a,bValues represent the average relative efficiencies of each IRES (± standard deviation) in HeLa, HepG2 and FRhK4 cells which are permissive for entero- and rhinoviral IRES activitya or in Neuro-2A, SKNBE, and BHK-21 cells which are not permissive for the type I IRESesb [adapted from Borman et al. (36)].
cThe values for translation efficiency in Neuro-2A cells were taken from Borman et al. (36). Values in parentheses represent the fold stimulation of IRES activity upon expression of 2A protease in these cells.
d,eValues are the averages of the results depicted in Figure 5 for the different polyadenylated IRES-p24 mRNAs translated at 10, 5 and 2.5 µg/ml final RNA concentration (expressed as percent of the most efficient mRNA).
eValues in parentheses represent the fold stimulation of translation efficiency mediated by inclusion of the Lb protease.
fValues are the averages of the results obtained with Op24-derived mRNAs translated in capped and polyadenylated form at 6, 3 and 1.5 µg/ml.
nd = not done.