Redox regulation of transcriptional activity of retinoic acid receptor by thioredoxin glutathione reductase (TGR)

The retinoic acid receptor (RAR), as one of the retinoic acid (RA)-responsive transcription activators, mediates various biological processes by regulating RA target gene expression. In studying how RAR activity is regulated, we isolated thioredoxin glutathione reductase (TGR), a member of the thioredoxin reductase family. Systematic yeast two-hybrid assays showed that in the presence of RA, TGR interacts with RAR via the LxxLL motif (NR box) located between the Grx and TrxR domains of TGR. This interaction was confirmed by GST pull-down and immunoprecipitation assays. The stable over-expression or knockdown of TGR in TGR-deficient NIH3T3 or TGR-abundant TM4 Sertoli cells, respectively, revealed that TGR enhances the transcriptional activity of RAR by increasing its DNA-binding capacity and restores RAR activity after impairment by reactive oxygen species (ROS). Furthermore, we demonstrated that the transactivation potential and DNA-binding activity of RAR in response to ROS depends on the cellular level of TGR. Overall, our data suggest that the redox regulation function of TGR protects the DNA-binding activity of RAR against cellular ROS damage.