FIGURE 11.
Working model for the differential regulation of the SNAT2 gene in HepG2 cells during activation of the AAR or UPR pathways. A, SNAT2-driven transcription is induced by either AAR or UPR from a plasmid-based luciferase reporter that contains the SNAT2 promoter and C/EBP-ATF site. In contrast, SNAT2 transcription from the endogenous gene is induced only by the AAR, but not by the UPR pathway. B, AAR pathway triggers assembly of the ATF4 enhanceosome, increased H3 acetylation, and preinitiation complex (PIC) formation, events that lead to enhanced SNAT2 transcription activity. Conversely, despite the assembly of the ATF4 enhanceosome, the UPR represses SNAT2 transcription.