Detection of a nuclear protein that interacts with a metal regulatory element of the mouse metallothionein 1 gene.

Metallothionein (MT) genes contain multiple metal regulatory elements (MREs) that are responsible for metal induction. A protein blotting procedure and a synthetic oligonucleotide have been used to identify nuclear factors interacting with a MRE (MREd) of the mouse MT-1 gene. We report the specific binding of the probe to a protein of apparent Mr 108,000 (p108). The specificity of the interaction was demonstrated by mutation analysis and competition experiments. Furthermore, the probe contains the Sp1 consensus binding sequence 5'CCGCCC3', in addition to the MRE consensus sequence, 5'TGCAC3', and we show that a Simian Virus 40 DNA fragment which contains six Sp1 binding sites did not bind p108 nor did it compete for the protein(s) interacting with MREd in a DNA footprinting assay. These results show that a metal regulatory element of the mouse MT-1 gene interacts specifically with a nuclear protein of Mr 108,000 and that this protein is distinct from the transcription factor Sp1.