As(III) transcriptionally activates the gadd45a gene via the formation of H₂O₂

Arsenic is a ubiquitous environmental contaminant associated with increased risks of human cancers of the skin, lung, bladder, and prostate. Intriguingly, it is also used to treat certain types of leukemia. It has recently been suggested that these paradoxic effects may be mediated by arsenic's ability to simultaneously activate DNA damage and apoptotic and transformation pathways. Here, we investigate the effects of arsenic exposure on the induction of the growth arrest and DNA damage protein 45α (GADD45α), which is thought to play roles in apoptosis, DNA damage response, and cell cycle arrest. We found that arsenic transcriptionally activates the gadd45α promoter located in a 153-bp region between -234 and -81, relative to the transcriptional start site. In addition, this transcriptional induction was abrogated in the presence of H₂O₂ scavengers, suggesting a role for H₂O₂ in the transcriptional control of the gadd45a gene through a Fenton-like free radical mechanism.