Heuchel, R.Radtke, F.Georgiev, O.Stark, G.Aguet, M.Schaffner, W.2006-12-052006-12-052006-12-05199410.1002/j.1460-2075.1994.tb06581.xhttps://infoscience.epfl.ch/handle/20.500.14299/2372888026472We 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.AnimalsBase SequenceCellsCulturedFungal Proteins/genetics/*metabolismGene Expression Regulation/*drug effectsMetallothionein/*biosynthesis/geneticsMetals/*pharmacologyMiceMolecular Sequence DataMutagenesisProtein Binding/drug effectsRNAMessenger/analysisRecombinationGenetic*Saccharomyces cerevisiae ProteinsStem CellsTranscription Factors/genetics/*metabolismZinc/pharmacologytext::journal::journal article::research article