Retinoic acid stimulation of the human surfactant protein B promoter is thyroid transcription factor 1 site-dependent.
Surfactant B (SP-B) is a 79-amino acid peptide critical to postnatal respiratory adaptation. Expression of SP-B by respiratory epithelial cells is regulated by developmental and hormonal influences at the level of gene transcription. Previous studies supported the role of retinoic acids (RA) and their receptors (RARs) in SP-B gene transcription. In the present study, RARalpha was detected in mouse alveolar type II epithelial cells where SP-B is synthesized and processed. Deletion and site-specific mutagenesis analysis identified clustered retinoic acid-responsive element sites in the 5'-flanking enhancer region of the hSP-B gene that bound RARalpha proteins. RAR coactivators ACTR, SRC-1, and transcriptional intermediary factor 2 (TIF2) stimulated human (h) SP-B promoter activity in a dose-dependent fashion in pulmonary adenocarcinoma H441 cells. In addition, an RAR-associated protein, CREB-binding protein (CBP), potentiated the effects of RAR on hSP-B promoter activity in H441 cells. Importantly, RA stimulation of the hSP-B promoter depends on tissue-specific thyroid transcription factor (TTF-1) DNA-binding sites. TTF-1 protein synergistically stimulated the hSP-B promoter with RARalpha, CBP, and nuclear receptor coactivators in H441 cells. In addition, TTF-1 interacted directly with RARalpha and TIF2 in the mammalian two-hybrid system. These findings support a model in which RAR/retinoid X receptor, TTF-1, coactivators, and CBP form a transcription activation complex in the upstream enhancer region of the hSP-B gene.
Naltner
A
A
Division of Pulmonary Biology, Children's Hospital Medical Center, Cincinnati, Ohio 45229-3039, USA.
Ghaffari
M
M
Whitsett
J A
JA
Yan
C
C
D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D050882:CREB-Binding Protein; D004847:Epithelial Cells / Q000378:metabolism; D006801:Humans; D051379:Mice; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009687:Nuclear Proteins / Q000378:metabolism*; D051958:Nuclear Receptor Coactivator 2; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D011510:Proteolipids / Q000096:biosynthesis / Q000235:genetics*; D011650:Pulmonary Alveoli / Q000378:metabolism*; D011663:Pulmonary Surfactants / Q000096:biosynthesis / Q000235:genetics*; D018168:Receptors, Retinoic Acid / Q000378:metabolism; D020218:Response Elements; D000072482:Retinoic Acid Receptor alpha; D000074482:Thyroid Nuclear Factor 1; D015534:Trans-Activators / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism*; D014212:Tretinoin / Q000494:pharmacology*; D020798:Two-Hybrid System Techniques
C498001:NCOA2 protein, human; C000614412:NKX2-1 protein, human; C498002:Ncoa2 protein, mouse; C000614414:Nkx2-1 protein, mouse; D009687:Nuclear Proteins; D051958:Nuclear Receptor Coactivator 2; D011510:Proteolipids; D011663:Pulmonary Surfactants; C000607071:RARA protein, human; C000607072:Rara protein, mouse; D018168:Receptors, Retinoic Acid; D000072482:Retinoic Acid Receptor alpha; D000074482:Thyroid Nuclear Factor 1; D015534:Trans-Activators; D014157:Transcription Factors; D014212:Tretinoin; D050882:CREB-Binding Protein; C494363:CREBBP protein, human; C494364:Crebbp protein, mouse