title: Thyroid transcription factor-1 (TTF-1) gene: identification of ZBP-89, Sp1, and TTF-1 sites in the promoter and regulation by TNF-α in lung epithelial cells.
abstract: Thyroid transcription factor-1 (TTF-1/Nkx2.1/TITF1) is a homeodomain-containing transcription factor essential for the morphogenesis and differentiation of the lung. In the lung, TTF-1 controls the expression of surfactant proteins that are essential for lung stability and lung host defense. In this study, we identified functionally important transcription factor binding sites in the TTF-1 proximal promoter and studied tumor necrosis factor-α (TNF-α) regulation of TTF-1 expression. TNF-α, a proinflammatory cytokine, has been implicated in the pathogenesis of acute respiratory distress syndrome (ARDS) and inhibits surfactant protein levels. Deletion analysis of TTF-1 5'-flanking DNA indicated that the TTF-1 proximal promoter retained high-level activity. Electrophoretic mobility shift assay, chromatin immunoprecipitation, and mutational analysis experiments identified functional ZBP-89, Sp1, Sp3, and TTF-1 sites in the TTF-1 proximal promoter. TNF-α inhibited TTF-1 protein levels in H441 and primary alveolar type II cells. TNF-α inhibited TTF-1 gene transcription and promoter activity, indicating that transcriptional mechanisms play important roles in the inhibition of TTF-1 levels. TNF-α inhibited TTF-1 but not Sp1 or hepatocyte nuclear factor-3 DNA binding to TTF-1 promoter. Transactivation experiments in A549 cells indicated that TNF-α inhibited TTF-1 promoter activation by exogenous Sp1 and TTF-1 without altering their levels, suggesting inhibition of transcriptional activities of these proteins. TNF-α inhibition of TTF-1 expression was associated with increased threonine, but not serine, phosphorylation of Sp1. Because TTF-1 serves as a positive regulator for surfactant protein gene expression, TNF-α inhibition of TTF-1 expression could have important implications for the reduction of surfactant protein levels in diseases such as ARDS.
authors.affiliation: Center for Biomedical Research, The University of Texas Health Center at Tyler, 75708-3154, USA.
authors.forename: Aparajita
authors.initials: A
authors.lastname: Das
authors.forename: Sunil
authors.initials: S
authors.lastname: Acharya
authors.forename: Koteswara Rao
authors.initials: KR
authors.lastname: Gottipati
authors.forename: James B
authors.initials: JB
authors.lastname: McKnight
authors.forename: Hemakumar
authors.initials: H
authors.lastname: Chandru
authors.forename: Joseph L
authors.initials: JL
authors.lastname: Alcorn
authors.forename: Vijay
authors.initials: V
authors.lastname: Boggaram
mesh_terms: D001483:Base Sequence; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D004847:Epithelial Cells / Q000378:metabolism* / Q000473:pathology; D006801:Humans; D008168:Lung / Q000378:metabolism* / Q000473:pathology; D008969:Molecular Sequence Data; D009154:Mutation; D009687:Nuclear Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D010766:Phosphorylation; D010957:Plasmids; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D012128:Respiratory Distress Syndrome / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D016329:Sp1 Transcription Factor / Q000235:genetics / Q000378:metabolism*; D051705:Sp3 Transcription Factor / Q000235:genetics / Q000378:metabolism*; D000074482:Thyroid Nuclear Factor 1; D014157:Transcription Factors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D015533:Transcriptional Activation; D014162:Transfection; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*
chemical_list: D004268:DNA-Binding Proteins; C000614412:NKX2-1 protein, human; D009687:Nuclear Proteins; D016329:Sp1 Transcription Factor; D000074482:Thyroid Nuclear Factor 1; D014157:Transcription Factors; D014409:Tumor Necrosis Factor-alpha; C110951:ZNF148 protein, human; D051705:Sp3 Transcription Factor