Ref-1 controls pax-8 DNA-binding activity.

Redox potential controls the DNA-binding activity of several transcription factors. In some cases, the regulation of DNA-binding activity by the redox state is mediated by the Ref-1 nuclear protein. In this study, we demonstrate that Ref-1 is able to induce "in vitro" the DNA-binding activity of the Pax-8 paired domain. In co-transfection experiments, Ref-1 increases the Pax-8 activating effect on thyroglobulin promoter. Moreover, immunoreactivity data suggest that, in nuclear extracts of thyroid cells, the levels of Ref-1 correlate with the amounts of reduced Pax-8. Therefore, the regulation of the Pax-8 DNA-binding activity by redox potential, that we have demonstrated occurring "in vitro", could represent a means to control "in vivo" the function of Pax proteins. Alignment of the Paired domains sequences present in the Protein Data Bank demonstrates a strong conservation of Cys residues, suggesting that the redox regulation of the Paired domain DNA-binding activity is widely conserved along phylogenesis.