OXIDATIVE STRESS ACTIVATES METAL-RESPONSIVE TRANSCRIPTION FACTOR-I BINDING-ACTIVITY - OCCUPANCY IN-VIVO OF METAL RESPONSE ELEMENTS IN THE METALLOTHIONEIN-I GENE PROMOTER

Oxidative stress (tert-butylhydroquinone) rapidly induced metallothion ein-I gene expression in mouse Hepa cells, and this effect was mediate d predominantly through metal response promoter elements in transient transfection assays. In vivo genomic footprinting of the mouse metallo thionein-I promoter after treatment of Hepa cells with hydrogen peroxi de, tert-butylhydroquinone, or zinc suggested a rapid increase in occu pancy of the metal response elements. More subtle changes also occurre d in the constitutive genomic footprint at the composite major late tr anscription factor/antioxidant response element. This element may, in part, mediate induction by hydrogen peroxide, Electrophoretic mobility shift assays demonstrated a rapid (30 min) increase in the DNA bindin g activity of metal-responsive transcription factor-1 in Hepa cells tr eated with any of these inducers, In control cells, upstream stimulato ry factor binding with the major late transcription factor site, and a nuclear protein complex distinct from AP-I, but specific for the anti oxidant response element, were detected, The amounts of these complexe s were not altered after these treatments, These studies indicate that metal-responsive transcription factor-1 plays a role in activating mo use metallothionein-I gene transcription in response to reactive oxyge n species.