Mechanisms of heavy metal sensing by metal response element-binding transcription factor-1

Abstract

Heavy metal homeostasis and detoxification systems are often regulated by changes in gene transcription. In higher eukaryotes, metal response element (MRE)-binding transcription factor-1 (MTF-1) is the only known metal-sensing transcription factor and zinc is the only heavy metal which can reversibly and directly activate the DNA-binding activity of MTF-1, leading to its nuclear retention, promoter binding and induction or repression of transcription. Although, cadmium, copper and oxidative stresses can cause the activation of the DNA-binding activity of MTF-1 in vivo, they apparently do so, at least in part, by causing the redistribution of intracellular zinc. MTF-1-dependentmetal- sensing transcription mechanisms are not fully understood but clearly involve zinc binding to its unique zinc finger domain. Recently, zinc has been shown to induce the formation of a co-activator complex containing MTF-1 and the histone acetyltransferase p300 which plays an essential role in the activation of mouse metallothionein-I (MT-I) gene transcription. In this review, we focus on current understanding of the mechanisms by which MTF-1 senses heavy metals and activates gene expression. ©2009 The Pharmaceutical Society of Japan.