Selective Damage to Antioxidant Gene Promoters in FA Cells

Abstract 2413

Oxidative stress has been implicated in the pathogenesis of many human diseases including Fanconi anemia (FA), a genetic disorder associated with bone marrow failure and progression to leukemia and other cancers. Here we show that several major anti-oxidant defense genes, including Glutathione peroxidase 1, Peroxiredoxin 3, Thioredoxin reductase 1, Superoxide dismutases 1, NAD(P)H:quinone oxireductase and Catalase, are down-regulated in bone marrow cells of FA patients. This gene down-regulation is selectively associated with increased oxidative DNA damage in the promoters of these anti-oxidant defense genes. Further, we show that both increased initial damage and reduced repair rate contribute to augmented oxidative DNA damage in FA cells. Using cell-based assays to assess promoter activity and damage repair kinetics, we demonstrate that FA proteins function to protect the promoter DNA from oxidative damage. Mechanistically, FA proteins appeared to act in concert with Brg1, a chromatin-remodeling ATPase subunit of the BAF complex. Specifically, Brg1 binds to the promoters of the anti-oxidant defense genes in steady state. Upon challenge with oxidative stress, FANCA and FANCD2 proteins are recruited to the promoter DNA, which correlates with significant increase in the binding of Brg1 within the promoter regions. Intriguingly, the formation of the FA-Brg1-promoter complex results in a marked decrease in nuclease hypersensitivity and oxidative damage in the promoter DNA in normal cells compared to FA cells. Finally, disassociation of the FA proteins from the Brg1-promoter complex parallels Pol II loading, suggesting a regulatory role for the FA proteins in transcription. Taken together, the study identifies a role of FA proteins in protecting anti-oxidant genes from oxidative damage.