Nuclear factor erythroid 2-related factor 2 (Nrf2) is the master regulator of a battery of genes, including the phase II genes, which respond to stressful conditions such as oxidative stress. Under basal conditions, Nrf2 is sequestered in the cytosol by kelch-like ECH-associated protein (Keap1), which targets it for proteasomal degradation involving Cul3 and E2 ubiquitin ligases. Keap1 has reactive cysteines, whose sulfhydration results in dissociation from Nrf2. Released Nrf2 translocates to the nucleus to regulate transcription of stress-responsive genes.