REVERSIBLE ZINC EXCHANGE BETWEEN METALLOTHIONEIN AND THE ESTROGEN-RECEPTOR ZINC-FINGER

We report here the first demonstration that reversible metal exchange occurs between metallothionein (MT) and full-length estrogen receptor (ER). Specific binding of ER to estrogen response element is inhibited in the presence of 40 mu M thionein and restored by 120 mu M zinc. Mo reover, ER in metal-depleted nuclear extracts exhibits reduced DNA bin ding which can be restored by 140 mu M native MT, Hence, thionein inhi bits DNA binding by abstracting zinc from functional ER while native M T is capable of restoring binding to metal-depleted extracts by donati ng metal to ER. This indicates MT may be an important physiological re gulator of intracellular zinc and/or other metals.