Figure 4. Transient up-regulation of translation for construct harboring ATF4 uORFs in responses to unfolded protein and oxidative stresses.
(A) The translation reporter construct regulated by ATF4 uORFs. The construct contains two upstream open reading frames (uORF1 and uORF2) before the open reading frame 3 (ORF3). The stop codon of uORF2 located downstream of the start codon of ORF3 is frame-shifted from ORF3 and thus does not affect translation the V4 peptide array and ODC contained in ORF3.
(B) and (D) Snapshots of the translation activity of the ATF4 reporter construct in a cell under DTT-induced stress (B) or NaAsO2-induced stress (D) at indicated time points. The full time course of the cell shown in (B) is shown in Movie S3. Scale Bars: 5 μm.
(C) and (E) Corresponding time course of the translation activity of the cell shown in (B) and (D), respectively. The translational activity is measured as the total intensity of the translation foci in the cell normalized to the initial value (average of the first 80s). 20–30 cells were measured for each treatment (NaAsO2 or DTT), and the ensemble-averaged time courses are shown in Figure S5.