Two domains of Nrf2 cooperatively bind CBP, a CREB binding protein, and synergistically activate transcription

Background: Nrf2 belongs to the Cap-N-Collar (CNC) transcription factor fam ily and is essential for the antioxidant responsive element (ARE)-mediated expression of a group of detoxifying and antioxidant genes. The forced expr ession of Nrf2 in mammalian cells activates the expression of target genes through the ARE, with Nrf2 showing the highest transactivation activity amo ng the CNC family of transcription factors. To elucidate the molecular mech anisms generating this potent transactivation activity, we examined the fun ctions of the domains within Nrf2. Result: We found that Nrf2 contains two transcription activation domains, N eh4 and Neh5, which act synergistically to attain maximum a activation of r eporter gene expression. Neh4 and Neh5 both individually and cooperatively bind to CBP (CREB (cAMP Responsive Element Binding protein) Binding Protein ). In fact, the specific inhibitor of CBP, adenovirus E1A protein, signific antly reduced Nrf2 activity. Importantly, the CBP-binding activity of Nrf2 deletion mutants positively correlated with their transactivation activity. Neh5 contains a motif which is commonly conserved among the CNC factors, w hereas Neh4 contains the novel CBP-interacting motif recently identified in p53 and E2F. Conclusions: Our results indicate that Nrf2 exploits the cooperative bindin g of two independent transactivation domains to CBP in the acquisition of a potent transactivation activity.