Activation of beta-catenin signalling increases StarD7 gene expression in JEG-3 cells.
StarD7 gene encodes a protein that belongs to the StAR-related lipid transfer proteins involved in intracellular transport and metabolism of lipids. It has been previously documented that StarD7 has a wide-spread mRNA expression in trophoblastic tissues and several tumour cell lines with highest levels in both choriocarcinoma JEG-3 and JAR cells, hepatocellular carcinoma HepG2, and colorectal adenocarcinoma HT-29 cells. To understand the molecular mechanisms that regulate the expression of the human StarD7 gene, we have cloned and characterized the 5'-flanking region of the gene. Transient transfections of several 5'deleted StarD7-promoter-firefly luciferase constructs into JEG-3 cells indicated that the -312/+157 region contains the gene minimal promoter. In addition, sequence analysis of a 1.6kb gene fragment revealed the presence of a TATA-less promoter as well as multiple regulatory motifs, including one regulatory element corresponding to the T-cell factor 4 (TCF4) binding site. Inhibition of glycogen synthase kinase-3beta (GSK3beta), a component of Wnt/beta-catenin signalling, increased both StarD7 mRNA and protein expression as well as its promoter activity. Co-transfection experiments in JEG-3 cell line revealed that the StarD7 promoter is activated by TCF4 transcription factor and by its beta-catenin coactivator. Moreover, site-directed mutagenesis of the TCF4 site located -614/-608bp relative to the transcription start site markedly diminished StarD7 promoter activity. Chromatin immunoprecipitation analysis demonstrated that beta-catenin and TCF4 are bound in vivo to the StarD7 gene promoter in JEG-3 cells treated with lithium chloride. Collectively, these studies show that beta-catenin and TCF4 activate the human StarD7 gene interacting with its promoter region through Wnt/beta-catenin signalling.
Rena
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V
Centro de Investigaciones en Bioquímica Clínica e Inmunología (CIBICI), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Departamento de Bioquímica Clínica, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Haya de la Torre y Medina Allende, Córdoba, Argentina.
Angeletti
S
S
Panzetta-Dutari
G
G
Genti-Raimondi
S
S
D051778:Basic Helix-Loop-Helix Leucine Zipper Transcription Factors / Q000235:genetics / Q000378:metabolism; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D045744:Cell Line, Tumor; D047369:Chromatin Immunoprecipitation; D017353:Gene Deletion; D015870:Gene Expression / Q000187:drug effects / Q000235:genetics; D015972:Gene Expression Regulation, Neoplastic / Q000502:physiology*; D017930:Genes, Reporter / Q000235:genetics; D038362:Glycogen Synthase Kinase 3 / Q000037:antagonists & inhibitors; D000071679:Glycogen Synthase Kinase 3 beta; D006801:Humans; D018021:Lithium Chloride / Q000494:pharmacology; D010766:Phosphorylation / Q000187:drug effects; D011401:Promoter Regions, Genetic / Q000187:drug effects / Q000235:genetics; D011485:Protein Binding / Q000187:drug effects / Q000235:genetics; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*; D000073940:Transcription Factor 4; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D014162:Transfection; D051176:beta Catenin / Q000235:genetics / Q000378:metabolism*
D051778:Basic Helix-Loop-Helix Leucine Zipper Transcription Factors; D002352:Carrier Proteins; C483475:STARD7 protein, human; C532096:TCF4 protein, human; D000073940:Transcription Factor 4; D014157:Transcription Factors; D051176:beta Catenin; C000605506:GSK3B protein, human; D000071679:Glycogen Synthase Kinase 3 beta; D038362:Glycogen Synthase Kinase 3; D018021:Lithium Chloride