title: Zinc sensing by metal-responsive transcription factor 1 (MTF1) controls metallothionein and ZnT1 expression to buffer the sensitivity of the transcriptome response to zinc.
abstract: Only a small number of genes are known direct targets of the zinc-responsive transcription factor MTF1; therefore, the aim of this study was to gain a more complete understanding of the MTF-1 regulated zinc-responsive component of the transcriptome. A targeted siRNA was used to deplete MTF1 expression in the human intestinal cell line Caco-2. We predicted that the response to zinc of direct MTF1 target genes would be abrogated by MTF1 knockdown. Surprisingly, a greater number of genes were regulated by zinc following MFT1 knockdown, and most genes that responded to zinc under both control and MTF1-depleted conditions had an augmented response in the latter condition. Exceptions were the zinc effluxer ZnT1 and a suite of metallothionein genes, suggesting that responses of other genes to zinc are usually buffered by increases in these proteins. We propose that MTF1 heads a hierarchy of zinc sensors, and through controlling the expression of a raft of metallothioneins and other key proteins involved in controlling intracellular zinc levels (e.g. ZnT1) alters zinc buffering capacity and total cellular zinc content. We tested and validated this model by overexpressing metallothionein and observing the predicted curtailment in response of the zinc-repressed SLC30A5 (ZnT5) promoter. The model provides the framework for an integrated understanding of cellular zinc homeostasis. Because MTs can bind metals other than zinc, this framework links with overall cellular metal homeostasis.
authors.affiliation: Institute for Cell and Molecular Biosciences, Newcastle University, Newcastle Upon Tyne, NE2 4NN, UK. dianne.ford@ncl.ac.uk.
authors.forename: J E J
authors.initials: JE
authors.lastname: Hardyman
authors.affiliation: Institute for Cell and Molecular Biosciences, Newcastle University, Newcastle Upon Tyne, NE2 4NN, UK. dianne.ford@ncl.ac.uk.
authors.forename: J
authors.initials: J
authors.lastname: Tyson
authors.affiliation: Institute for Cell and Molecular Biosciences, Newcastle University, Newcastle Upon Tyne, NE2 4NN, UK. dianne.ford@ncl.ac.uk.
authors.forename: K A
authors.initials: KA
authors.lastname: Jackson
authors.affiliation: Institute for Cell and Molecular Biosciences, Newcastle University, Newcastle Upon Tyne, NE2 4NN, UK. dianne.ford@ncl.ac.uk.
authors.forename: C
authors.initials: C
authors.lastname: Aldridge
authors.affiliation: Faculty of Medical Sciences, Newcastle University, Newcastle Upon Tyne, NE2 4NN, UK.
authors.forename: S J
authors.initials: SJ
authors.lastname: Cockell
authors.affiliation: School of Dental Sciences, Newcastle University, Newcastle Upon Tyne, NE2 4NN, UK.
authors.forename: L A
authors.initials: LA
authors.lastname: Wakeling
authors.affiliation: School of Dental Sciences, Newcastle University, Newcastle Upon Tyne, NE2 4NN, UK.
authors.forename: R A
authors.initials: RA
authors.lastname: Valentine
authors.affiliation: Institute for Cell and Molecular Biosciences, Newcastle University, Newcastle Upon Tyne, NE2 4NN, UK. dianne.ford@ncl.ac.uk.
authors.forename: D
authors.initials: D
authors.lastname: Ford
mesh_terms: D018938:Caco-2 Cells; D027682:Cation Transport Proteins / Q000235:genetics / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000378:metabolism*; D017353:Gene Deletion; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation / Q000187:drug effects; D055785:Gene Knockdown Techniques; D006801:Humans; D008668:Metallothionein / Q000235:genetics / Q000378:metabolism*; D005810:Multigene Family; D020411:Oligonucleotide Array Sequence Analysis; D011401:Promoter Regions, Genetic / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D015203:Reproducibility of Results; D014157:Transcription Factors / Q000378:metabolism*; D059467:Transcriptome / Q000187:drug effects / Q000235:genetics*; D015032:Zinc / Q000494:pharmacology*; D000097809:Transcription Factor MTF-1
chemical_list: D027682:Cation Transport Proteins; D004268:DNA-Binding Proteins; D008668:Metallothionein; D012333:RNA, Messenger; D014157:Transcription Factors; D015032:Zinc; D000097809:Transcription Factor MTF-1; C498299:SLC30A1 protein, human; C457225:SLC30A5 protein, human