title: Characterization of cis-acting elements in the promoter of the mouse metallothionein-3 gene. Activation of gene expression during neuronal differentiation of P19 embryonal carcinoma cells.
abstract: The metallothionein (MT)3 gene is expressed predominantly in the brain and the organs of the reproductive system, and fails to respond to metal ions in vivo. A CTG repeat was proposed to function as a potential repressor element in nonpermissive cells, and a sequence similar to the JC virus silencer element was found to function as a negative element in permissive primary astrocytes. The objective of this study was to characterize further the mechanisms governing cell-type specific MT-3 gene transcription. We searched for a suitable cell line expressing the MT-3 gene to be used for determination of MT-3 promoter tissue specificity, and showed that MT-3 expression is activated during neuroectodermal differentiation of P19 cells induced by retinoic acid to levels similar to those found in whole brain. Deletion of the CTG repeat or of the JC virus silencer did not promote MT-3 promoter activity in nonpermissive cells, or enhance expression in permissive cells. We identified MT-3 promoter sequences interacting with liver and brain nuclear proteins, as assayed by DNase I footprinting analyses and electrophoretic mobility shift assay, and assessed the role of these sequences in the regulation of MT-3 expression by cotransfection experiments. We generated stable transfectants in permissive C6 and nonpermissive NIH-3T3 cells, and analysed the methylation status of the MT-3 gene. These studies show that regulation of tissue-specific MT-3 gene expression does not appear to involve a repressor, and suggest that other mechanisms such as chromatin organization and epigenetic modifications could account for the absence of MT-3 gene transcription in nonpermissive cells.
authors.affiliation: Centre de recherche en cancérologie de l'Université Laval, and Département d'anatomie et physiologie, Faculté de médecine, Université Laval, Québec, Canada.
authors.forename: R
authors.initials: R
authors.lastname: Faraonio
authors.forename: P
authors.initials: P
authors.lastname: Moffatt
authors.forename: O
authors.initials: O
authors.lastname: Larochelle
authors.forename: H M
authors.initials: HM
authors.lastname: Schipper
authors.forename: R
authors.initials: R
authors.lastname: S-Arnaud
authors.forename: C
authors.initials: C
authors.lastname: Séguin
mesh_terms: D016475:3T3 Cells; D000818:Animals; D001483:Base Sequence; D019556:COS Cells; D002454:Cell Differentiation / Q000187:drug effects; D002478:Cells, Cultured; D002522:Chlorocebus aethiops; D004247:DNA / Q000378:metabolism; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006801:Humans; D008668:Metallothionein / Q000096:biosynthesis / Q000235:genetics*; D000090023:Metallothionein 3; D051379:Mice / Q000235:genetics*; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009369:Neoplasms / Q000473:pathology; D009374:Neoplasms, Experimental / Q000473:pathology; D009457:Neuroglia / Q000166:cytology; D009474:Neurons / Q000166:cytology*; D011401:Promoter Regions, Genetic / Q000235:genetics*; D012333:RNA, Messenger / Q000096:biosynthesis; D012334:RNA, Neoplasm / Q000096:biosynthesis; D051381:Rats; D017207:Rats, Sprague-Dawley; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis; D013045:Species Specificity; D018243:Teratocarcinoma / Q000235:genetics / Q000473:pathology*; D015533:Transcriptional Activation; D014162:Transfection; D014212:Tretinoin / Q000494:pharmacology; D014407:Tumor Cells, Cultured / Q000187:drug effects
chemical_list: D000090023:Metallothionein 3; C000715430:Mt3 protein, mouse; D012333:RNA, Messenger; D012334:RNA, Neoplasm; D011993:Recombinant Fusion Proteins; D014212:Tretinoin; D004247:DNA; D008668:Metallothionein