The transcription factor MTF-1 is essential for basal and heavy metal-induced metallothionein gene expression
We have described and cloned previously a factor (MTF-1) that binds specifically to heavy metal-responsive DNA sequence elements in the enhancer/promoter region of metallothionein genes. MTF-1 is a protein of 72.5 kDa that contains six zinc fingers and multiple domains for transcriptional activation. Here we report the disruption of both alleles of the MTF-1 gene in mouse embryonic stem cells by homologous recombination. The resulting null mutant cell line fails to produce detectable amounts of MTF-1. Moreover, due to the loss of MTF-1, the endogenous metallothionein I and II genes are silent, indicating that MTF-1 is required for both their basal and zinc-induced transcription. In addition to zinc, other heavy metals, including cadmium, copper, nickel and lead, also fail to activate metal-responsive promoters in null mutant cells. However, cotransfection of an MTF-1 expression vector and metal-responsive reporter genes yields strong basal transcription that can be further boosted by zinc treatment of cells. These results demonstrate that MTF-1 is essential for metallothionein gene regulation. Finally, we present evidence that MTF-1 itself is a zinc sensor, which exhibits increased DNA binding activity upon zinc treatment.
- URL: http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&dopt=Citation&list_uids=8026472
Keywords: Animals ; Base Sequence ; Cells ; Cultured ; Fungal Proteins/genetics/*metabolism ; Gene Expression Regulation/*drug effects ; Metallothionein/*biosynthesis/genetics ; Metals/*pharmacology ; Mice ; Molecular Sequence Data ; Mutagenesis ; Protein Binding/drug effects ; RNA ; Messenger/analysis ; Recombination ; Genetic ; *Saccharomyces cerevisiae Proteins ; Stem Cells ; Transcription Factors/genetics/*metabolism ; Zinc/pharmacology
Institut fur Molekularbiologie II, Universitat Zurich, Switzerland.
Record created on 2006-12-05, modified on 2016-08-08