FIG. 8.

Effects of overexpression of ATF6 mutants on the activities of the human GRP78, XBP-1, and CHOP promoters. (A) Schematic structures of full-length ATF6 and two mutants, ATF6 (373) and ATF6 (373) ΔAD. The locations of the activation domain (AD), bZIP region, and transmembrane domain (TMD) are marked. Numbers indicate amino acid positions relative to the N terminus. (B) Structures of intact and mutant promoters cloned immediately upstream of the firefly luciferase gene are shown schematically as in Fig. 4. A reporter plasmid and the pRL-SV40 reference plasmid were transfected into HeLa cells together with pcDNA3.1(+) (vector) or one of the mutant ATF6 expression plasmids pcDNA-ATF6 (373) and pcDNA-ATF6 (373) ΔAD as described in Materials and Methods. The relative luciferase activity in transfected cells incubated for 16 h with (solid boxes) or without (open boxes) 2 μg of tunicamycin (TM)/ml was determined, and averages from four independent experiments are presented with standard deviations (error bars).