FIG. 5.

uORF represses translation initiation at the M1 AUG. HOS cells were transiently transfected with plasmids producing mouse RNase H1 fused to Renilla luciferase. Luciferase activity is detected only from proteins initiated at the M1 AUG (A) or at the M27 AUG (B and C). Plasmids contain mutations as indicated by ΔT (one-thymine-base deletion), +T (one-thymine-base insertion), AUC (AUG-to-AUC substitution), and “no-term” (in which the termination codon of uORF, UGA, was changed to GGA). Black thick arrows represent ORFs fused to the luciferase gene. ORFs shown by gray arrows have termination codons before the luciferase gene. Bar graphs represents the mean ± standard deviation (SD) of luciferase activity (n = 3) of HOS cells transfected with the indicated plasmid.