title: Modulation of Sp1 and Sp3 in lung epithelial cells regulates ClC-2 chloride channel expression.
abstract: ClC-2 is a pH- and voltage-activated chloride channel, which is highly expressed in fetal airways and downregulated at birth. The ClC-2 promoter contains consensus binding sites within the first 237 bp, which bind transcription factors Sp1 and Sp3(1). This study directly links Sp1 and Sp3 with ClC-2 protein expression by demonstrating: (i) induction of ClC-2 protein by transient overexpression of each transcription factor in adult rat Type II cells, which have low levels of ClC-2; and (ii) reduction of ClC-2 expression by incubation with a competitive inhibitor of Sp1 and Sp3 in fetal rat Type II cells, which have high levels of endogenous ClC-2. Endogenous fetal lung Sp1 is differentially expressed as two major species of 105 kD and 95 kD. Although low-level expression of Sp1 in adult cells is almost exclusively the 105-kD species, overexpression of Sp1 results in increased expression of the 95-kD band. These experiments suggest that the mechanism for postnatal reduction of ClC-2 expression in lung epithelia is based on decreased interaction of Sp1 and Sp3 with the ClC-2 promoter.
authors.affiliation: Eudowood Division of Pediatric Respiratory Sciences, The Johns Hopkins Medical Institutions, 600 N Wolfe St. Park 316, Baltimore, MD 21287-2533, USA.
authors.forename: Kathryn W
authors.initials: KW
authors.lastname: Holmes
authors.forename: Russell
authors.initials: R
authors.lastname: Hales
authors.forename: Shijian
authors.initials: S
authors.lastname: Chu
authors.forename: Micah J
authors.initials: MJ
authors.lastname: Maxwell
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Mogayzel
authors.forename: Pamela L
authors.initials: PL
authors.lastname: Zeitlin
mesh_terms: D000375:Aging / Q000235:genetics / Q000378:metabolism; D000818:Animals; D000090007:CLC-2 Chloride Channels; D002454:Cell Differentiation / Q000235:genetics; D002460:Cell Line; D018118:Chloride Channels / Q000235:genetics / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D015536:Down-Regulation / Q000187:drug effects / Q000235:genetics; D005260:Female; D018507:Gene Expression Regulation, Developmental / Q000187:drug effects / Q000235:genetics*; D005822:Genetic Vectors; D008168:Lung / Q000166:cytology / Q000254:growth & development / Q000378:metabolism*; D008926:Plicamycin / Q000031:analogs & derivatives* / Q000494:pharmacology; D011401:Promoter Regions, Genetic / Q000187:drug effects / Q000235:genetics; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D051381:Rats; D011993:Recombinant Fusion Proteins; D020545:Respiratory Mucosa / Q000166:cytology / Q000254:growth & development / Q000378:metabolism*; D016329:Sp1 Transcription Factor / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D051705:Sp3 Transcription Factor; D014157:Transcription Factors / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*
chemical_list: D000090007:CLC-2 Chloride Channels; D018118:Chloride Channels; D004268:DNA-Binding Proteins; D020033:Protein Isoforms; D011993:Recombinant Fusion Proteins; D016329:Sp1 Transcription Factor; C497123:Sp3 protein, rat; D014157:Transcription Factors; D051705:Sp3 Transcription Factor; C066851:mithramycin A; D008926:Plicamycin