Fig 1: Differential expression of proteasomal genes regulated by Nrf1-independent pathway under reductive stress induced by DTT. (A) Four genotypic cell lines of WT, Nrf1a-/-, Nrf2-/-?TA and caNrf2?N were (or were not) treated with 1 mM DTT for 0 to 24 h, before both basal and DTT-inducible mRNA expression levels of core proteasomal subunit genes (i.e., PSMB5 (A1), PSMB6 (A2) and PSMB7 (A3)) were determined by RT-qPCR. The resulting data were shown as fold changes (mean ± SD, n = 3 × 3), which are representative of at least three independent experiments, each performed in triplicate. Significant increases ($, p < 0.05) and significant decreases (* p < 0.05; ** p < 0.01) were statistically calculated by comparison with their corresponding controls (measured at 0 h). (B) These proteasomal protein expression levels in four distinct cell lines were determined by Western blotting with their indicated antibodies, such PSMB5 (b1, b5, b9, b13), PSMB6 (b2, b6, b10, b14) and PSMB 7(b3, b7, b11, b15), whilst ß-actin served as a loading control. The intensity of those immunoblots, representing different protein expression levels, was also quantified by the Quantity One 4.6.2 software, as shown on bottom (C). A model was proposed to provide a better explanation of distinct roles for Nrf1 and Nrf2 in DTT-stimulated reductive stress response, along with ER stress signaling and relevant redox metabolism.