Redox regulation of the transcriptional repressor Bach1.

Bach1 is a transcriptional repressor of heme oxygenase-1, one of the most inducible phase 2 proteins. Bach1 binds in conjunction with a small Maf protein to tandem repeats of the antioxidant response element (ARE) and quenches the target gene expression. On the other hand, the transactivator Nrf2 binds and up-regulates the ARE-governed gene expression. By using a sulfhydryl oxidizing agent, diamide, here we provide evidence which indicates that the Bach1 function is regulated by the redox state. Diamide showed restricted Nrf2 nuclear translocation and ARE-driven reporter activity but reversed the ARE transcriptional activity suppressed by ectopically expressed Bach1. Substitution of the conserved cysteine residue in the DNA binding domain of Bach1 to serine (C574S mutant) caused a refractory response to the diamide-mediated reactivation of the Bach1-suppressed reporter activity. Moreover, diamide induced cytoplasmic translocation of the GFP-Bach1 fusion protein but failed to translocate the fusion protein consisting of the C574S mutant. These data suggest that redox regulation of Bach1 is an alternative mechanism to induce multiple ARE-governed genes.