-To investigate the adaptive response to the environmental electrophile methylmercury (MeHg), we performed DNA microarray analysis of human neuroblastoma SH-SY5Y cells exposed to a sub-cytotoxic dose of MeHg (1 μM) for 6 hr. The expression of 15 genes increased 10-fold or more in response to MeHg. Four of these genes are associated with detoxification and excretion of MeHg into the extracellular space, and are regulated by transcription factor Nrf2 through the electrophile response element. Interestingly, Cullin3, a negative regulator of Nrf2, was identified as a down-regulated gene during MeHg exposure.