title: Activation of an SP binding site is crucial for the expression of claudin 1 in rat epididymal principal cells.
abstract: Claudin 1 (CLDN1) is a tight junctional protein present in the epididymis. Limited information exists regarding the regulation of Cldn1 transcription. In the epididymis, the regulation of the 5' flanking region of genes coding for tight junctional proteins is unknown. The present objectives were to investigate the transcriptional regulation of the Cldn1 gene in the rat epididymis. A 1.8-kb sequence of the 5' flanking region of the rat Cldn1 gene was cloned. The transcriptional start site is an adenine located at the -198 position relative to the first codon, and 26 bp downstream of the putative TATA box. It is the only start site for the Cldn1 gene transcription in the rat epididymis. The Cldn1 promoter was inserted into a luciferase gene expression vector and transfected into a rat caput epididymal cell line (RCE-1). Sequential deletion analysis revealed that minimal promoter activity was achieved with the construct containing -61 to +164 bp of the promoter. This sequence contained a TATA box and two consensus SP1 binding sites. Electrophoretic mobility shift and supershift assays confirmed that SP1 and SP3 were present in RCE-1 cells and epididymal nuclear extracts, and that they bind to the 5' SP1 binding motif of the promoter. Site-directed mutagenesis of the 5' SP1 binding site resulted in a 4-fold decrease in transactivation of the minimal promoter sequence. These findings indicate that SP1 and SP3 bind to the Cldn1 promoter region, and that this interaction influences the expression of Cldn1 in the rat epididymis.
authors.affiliation: INRS-Institut Armand-Frappier, Université du Québec, Pointe Claire, Québec, Canada H9R 1G6.
authors.forename: Julie
authors.initials: J
authors.lastname: Dufresne
authors.forename: Daniel G
authors.initials: DG
authors.lastname: Cyr
mesh_terms: D024506:5' Flanking Region / Q000235:genetics; D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D001711:Biotransformation; D002478:Cells, Cultured; D062445:Claudin-1; D024202:Electrophoretic Mobility Shift Assay; D004822:Epididymis / Q000166:cytology / Q000378:metabolism*; D017930:Genes, Reporter / Q000235:genetics; D008156:Luciferases / Q000235:genetics; D008297:Male; D008565:Membrane Proteins / Q000096:biosynthesis*; D021141:Nucleic Acid Amplification Techniques; D010957:Plasmids / Q000235:genetics; D051381:Rats; D016329:Sp1 Transcription Factor / Q000378:metabolism*; D019108:Tight Junctions / Q000378:metabolism; D014162:Transfection
chemical_list: D062445:Claudin-1; C568114:Cldn1 protein, rat; D008565:Membrane Proteins; D016329:Sp1 Transcription Factor; D008156:Luciferases