A RIPE3b1-like factor binds to a novel site in the human insulin promoter in a redox-dependent manner

In the human insulin gene, a regulatory sequence upstream of the transcription start site at -229 to -258 (the E2 element) binds a ubiquitous factor USF. The present study led to the identification of a second factor, D0, that binds to an adjacent upstream site, the C2 element, that has previously not been described. The results demonstrate that D0 exhibits similar properties to RIPE3b1, a factor shown to be an important determinant of insulin gene beta-cell-specific expression. Binding of D0 to the C2 element was abolished by the oxidising agent diamide, and the alkylating agent N-ethylmaleimide. The results indicate that expression of the insulin gene may be regulated by a redox-dependent pathway involving RIPE3b1 or a RIPE3b1-like factor.