Characterization of the DNA-Binding Properties of the Early Growth Response-1 (Egr-1) Transcription Factor: Evidence for Modulation by a Redox Mechanism

The binding of the transcription factor early growth response-1 (Egr-1) to its specific DNA-binding sequence GCGGGGGCG occurs through the interaction of three zinc finger motifs. DNA binding by Egr-1 can be modified by alteration of reduction–oxidation (redox) state. Using gel retardation assays, we show that binding of Egr-1 protein is specific and is dependent on the presence of reducing agents in a dose-dependent manner. The zinc finger region is the domain subject to conformation changes by redox. Oxidized or metal-free Egr-1 does not bind. Nuclear extracts of several cell types contain a heat-sensitive factor(s) that induces the ability of Egr-1 protein to bind to DNA in otherwise suboptimal conditions containing insufficient reducing agent. This inducing activity may be replaced by Ref-1, a protein identified and characterized by Curran and co-workers (Xanthoudakis and Curran, 1992). The possibility arises that the transcription-regulating activity of Egr-1 may be regulated by the redox state in the cell via factors such as Ref-1 that modulate its DNAbinding activity.