Switch from Cap- to Factorless IRES-Dependent 0 and +1 Frame Translation during Cellular Stress and Dicistrovirus Infection

Wang, Qing S.; Jan, Eric

A similar result is observed with cells treated with PatA and 4E1Rcat. Cap-dependent RLuc translation was significantly inhibited with increasing amounts of PatA treatment ( Figure 5D ). At 200 nM PatA, cap-dependent translation was inhibited by 60-80% ( Figure 5D ). In contrast, CrPV and IAPV IGR IRESdependent 0 frame FLuc translation was stimulated under PatA treatments but to different extents. IAPV IGR IRES translation increased by approximately 2 to 6 fold under increasing concentrations of PatA ( Figure 5D ) whereas CrPV IGR IRES translation was stimulated 12 fold at the highest concentration of PatA ( Figure 5D ). Similarly, IAPV IGR IRES +1 frame translation was stimulated to the same extent during PatA treatment as 0 frame translation ( Figure 5D ). 4E1Rcat at 8 mM had a moderate inhibitory effect on capdependent translation by only 40-70% ( Figure 5E ). At higher 4E1RCat concentrations, both cap-dependent and IRES-dependent translation was significantly inhibited (data not shown). In contrast, 4E1RCat treatment at 8 mM stimulated CrPV and IAPV IGR IRES 0 frame translation by only approximately 1.2-1.5 fold ( Figure 5E ). 4E1RCat treatment also stimulated IAPV IGR IRES +1 frame translation by ,1.3 fold whereas this treatment did not stimulate +1 frame translation with the IAPV IGR IRES DPKI mutant construct ( Figure 5E ). In summary, these results showed that IGR IRES-mediated 0 and +1 frame translation are stimulated in S2 cells to the same extent under different cellular stress conditions when overall translation is compromised.