A nuclear factor requires Zn2+ to bind a regulatory MRE element of the mouse gene encoding metallothionein-1

The metal ion requirement of nuclear proteins for binding to the metal regulatory element d(MREd) of the mouse gene encoding metallothionein-1 was investigated using an in vitro exonuclease III footprinting assay. The specific DNA-binding activity of the factor was inactivated by the chelating agents, EDTA and 1,10-phenanthroline. Binding activity was restored by Zn2+, but not by Cd2+. These results show that Zn2+ ions are a required component for specific in vitro DNA binding of the MREd-binding protein.