Glucocorticoid responsiveness conferred by a cloned DNA binding protein.
Glucocorticoids stimulate surfactant protein-B (SP-B) (expression in type II alveolar cells) by unknown mechanisms. We identified, cloned, and characterized a protein that binds the SP-B promoter. This protein, D, increases the activity of the SP-B promoter in response to glucocorticoid stimulation. Protein D was identified by its ability to bind the SP-B promoter region, which it binds at an NF1 site from -184 to -198 bp. Its binding was abolished by digestion of promoter DNA with BalI, which cuts at -194. Protein D was cloned and sequenced. It is a new DNA binding protein of 33 kDa whose carboxyl end contains a modified basic leucine zipper-like DNA binding motif (bzip). The effects of D on SP-B promoter activity were studied in H441 cells, using a reporter construct containing 212 bp from the SP-B promoter with a luciferase reporter gene (p2121uc), which was cotransfected with a protein D expression construct in which D expression was controlled by the SV40 early promoter. These two plasmids were cotransfected into H441 cells. Without added glucocorticoids, D did not alter SP-B promoter activity. When dexamethasone was added, D strongly enhanced SP-B promoter activity. Identification of this protein suggests that, at least for SP-B, glucocorticoid responsiveness may involve one or more hitherto unknown gene activators.
Luzi
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P
Department of Pathology, Anatomy, and Cell Biology, Jefferson Medical College, Philadelphia, PA, USA.
Anceschi
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M
Strayer
D S
DS
D000595:Amino Acid Sequence; D000818:Animals; D018076:DNA, Complementary / Q000235:genetics; D003907:Dexamethasone / Q000494:pharmacology*; D005786:Gene Expression Regulation; D015723:Gene Library; D017930:Genes, Reporter; D006023:Glycoproteins / Q000235:genetics*; D006801:Humans; D016350:Leucine Zippers; D008168:Lung / Q000737:chemistry*; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic / Q000235:genetics; D011510:Proteolipids / Q000096:biosynthesis / Q000235:genetics*; D037663:Pulmonary Surfactant-Associated Protein D; D011663:Pulmonary Surfactants / Q000096:biosynthesis / Q000235:genetics*; D011817:Rabbits; D011987:Receptors, Steroid / Q000235:genetics; D011994:Recombinant Proteins / Q000096:biosynthesis; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid
D018076:DNA, Complementary; D006023:Glycoproteins; D011510:Proteolipids; D037663:Pulmonary Surfactant-Associated Protein D; D011663:Pulmonary Surfactants; D011987:Receptors, Steroid; D011994:Recombinant Proteins; D003907:Dexamethasone