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. 2019 Nov 11;42(11):783–793. doi: 10.14348/molcells.2019.0104

Fig. 5. Schematic diagram of the reporter system for monitoring RIP of ATF6α.

Fig. 5

The RIP reporter cell line carries two stably integrated expression constructs. The first construct is a firefly luciferase gene controlled by a synthetic promoter comprising five direct repeats of yeast GAL4-binding site (GAL4 Upstream Activating Sequences [GAL4 UAS]) and TATA box. The second expression cassette is composed of a fusion gene encoding GAL4DBD and the VP16AD followed by the N-terminal deletion variant of ATF6α (ATF6αΔN(aa 333–670)). In the absence of ER stress, the localization of GAL4DBD-VP16AD(GV)-ATF6αΔN(aa 333–670) protein is restricted at the ER membrane; therefore, there is no significant expression of the firefly luciferase gene because of the absence of active transcription factors. However, under ER stress, the GV-ATF6αΔN(aa 333–670) is translocated to the Golgi apparatus for cleavage by S1P and S2P. The cytosolic N-terminal fragment GV-ATF6αΔNΔC(aa 333–380) is translocated into the nucleus to bind with the GAL4-binding site (GAL4 UAS) as an active transcription factor and induces the expression of firefly luciferase.