Upstream enhancer activity in the human surfactant protein B gene is mediated by thyroid transcription factor 1.
Surfactant protein B (SP-B) is selectively expressed in bronchiolar and alveolar epithelial cells of the lung. We identified an upstream enhancer located in the 5'-flanking region of the human SP-B gene (-439 to -331 base pair, hSP-B(-439/-331)) by deletion analysis of SP-B-luciferase constructs assessed in transfection assays in vitro. The element cis-activated the expression of an SV40 promoter-luciferase reporter gene in a human pulmonary adenocarcinoma cell line (H441-4). Three distinct binding sites for the nuclear transcription protein, thyroid transcription factor 1 (TTF-1), were identified, and the purified TTF-1 homeodomain was bound to bhe region of hSP-B(-439/-331). Co-transfection of H441-4 cells with the expression vector pCMV-TTF-1 trans-activated the native human SP-B promoter and the SV40 promoter fused with the SP-B enhancer. Mutations of the TTF-1 binding sites in the upstream enhancer blocked TTF-1 binding and transactivation activity. In summary, TTF-1 interacts with distinct proximal (-80 to -110) and distal (-439 to -331) cis-acting elements than regulate lung epithelial cell-specific transcription of the human SP-B gene.
Yan
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Children's Hospital Medical Center, Division of Pulmonary Biology, Cincinnati, Ohio 45229-3039, USA.
Sever
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Z
Whitsett
J A
JA
D001483:Base Sequence; D004247:DNA / Q000378:metabolism; D004742:Enhancer Elements, Genetic; D018398:Homeodomain Proteins / Q000502:physiology*; D006801:Humans; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000502:physiology*; D011401:Promoter Regions, Genetic; D011510:Proteolipids / Q000235:genetics*; D011663:Pulmonary Surfactants / Q000235:genetics*; D013539:Simian virus 40 / Q000235:genetics; D013937:Thymidine Kinase / Q000235:genetics; D000074482:Thyroid Nuclear Factor 1; D014157:Transcription Factors / Q000502:physiology*
D018398:Homeodomain Proteins; C000614412:NKX2-1 protein, human; D009687:Nuclear Proteins; D011510:Proteolipids; D011663:Pulmonary Surfactants; D000074482:Thyroid Nuclear Factor 1; D014157:Transcription Factors; D004247:DNA; D013937:Thymidine Kinase