Fig. 6. Mist1 activates expression of a Cx32 reporter gene. (A) AR42J exocrine pancreatic cells were electroporated with the Cx32 luciferase reporter (Cx32p-Luc) gene and an expression plasmid encoding the Mist1 cDNA. Mist1 protein is able to induce Cx32p-Luc expression approximately 15- to 20-fold. (B) A variety of other bHLH factors (both Class A and Class B) were examined for their ability to activate expression of the Cx32p-Luc gene. Only Mist1 is capable of activating this reporter gene. (C) Transfection of AR42J cells with the Cx32p-Luc and different Mist1 gene constructs confirms that DNA binding mutants (Mist1^{mut basic}, mbasic) and protein dimerization mutants (Mist1^{mut helix 1}, mhelix 1) are unable to activate expression of the Cx32p-Luc gene. Error bars indicate the standard error of the mean for a minimum of three independent transfections per gene construct.