Figure 4.

Both ATF4 uORFs are translated under basal conditions. (A) Predicted structure of the mRNA expressed by the reporter genes used in these experiments. (B) Autoradiograms of SDS-PAGE of radiolabeled proteins from untreated and AP20187-treated Fv2E-PERK⁽⁺⁾ CHO cells transfected with the ATF4-GFP reporter, or reporters fusing uORF1 or uORF2 to GFP. Cytoplasmic RNA from a parallel sample of untreated, transfected cells was resolved by Northern blot and hybridized to GFP and GAPDH probes. The low basal expression of NPTII in cells transfected with the uORF1-GFP is a reproducible if unexplained finding.