The lung-specific surfactant protein B gene promoter is a target for thyroid transcription factor 1 and hepatocyte nuclear factor 3, indicating common factors for organ-specific gene expression along the foregut axis.
We used the lung epithelial cell-specific surfactant protein B (SPB) gene promoter as a model with which to investigate mechanisms involved in transcriptional control of lung-specific genes. In a previous study, we showed that the SPB promoter specifically activated expression of a linked reporter gene in the continuous H441 lung cell line and that H441 nuclear proteins specifically protected a region of this promoter from bp -111 to -73. In this study, we further show that this region is a complex binding site for thyroid transcription factor 1 (TTF-1) and hepatocyte nuclear factor 3 (HNF-3). Whereas TTF-1 bound two highly degenerate and closely spaced sites, HNF-3 proteins bound a TGT3 motif (TGTTTGT) that is also found in several liver-specific gene regulatory regions, where it appears to be a weak affinity site for HNF-3. Point mutations of these binding sites eliminated factor binding and resulted in significant decreases in transfected SPB promoter activity. In addition, we developed a cotransfection assay and showed that a family of lung-specific gene promoters that included the SPB, SPC, SPA, and Clara cell secretory protein (CCSP) gene promoters were specifically activated by cotransfected TTF-1. We conclude that TTF-1 and HNF-3 are major activators of lung-specific genes and propose that these factors are involved in a general mechanism of lung-specific gene transcription. Importantly, these data also show that common factors are involved in organ-specific gene expression along the mammalian foregut axis.
Bohinski
R J
RJ
Division of Pulmonary Biology, Children's Hospital Medical Center, Cincinnati, Ohio 45229-2899.
Di Lauro
R
R
Whitsett
J A
JA
D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D004268:DNA-Binding Proteins / Q000502:physiology*; D005786:Gene Expression Regulation; D051541:Hepatocyte Nuclear Factor 3-alpha; D051542:Hepatocyte Nuclear Factor 3-beta; D066298:In Vitro Techniques; D008099:Liver / Q000502:physiology; D008168:Lung / Q000502:physiology*; D051379:Mice; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000502:physiology*; D011401:Promoter Regions, Genetic; D011510:Proteolipids / Q000235:genetics*; D011663:Pulmonary Surfactants / Q000235:genetics*; D012333:RNA, Messenger / Q000235:genetics; D013961:Thyroid Gland / Q000502:physiology; D000074482:Thyroid Nuclear Factor 1; D014157:Transcription Factors / Q000235:genetics* / Q000502:physiology*; D015533:Transcriptional Activation
D004268:DNA-Binding Proteins; C496500:Foxa1 protein, mouse; C496503:Foxa2 protein, mouse; D051541:Hepatocyte Nuclear Factor 3-alpha; C000614414:Nkx2-1 protein, mouse; D009687:Nuclear Proteins; D011510:Proteolipids; D011663:Pulmonary Surfactants; D012333:RNA, Messenger; D000074482:Thyroid Nuclear Factor 1; D014157:Transcription Factors; D051542:Hepatocyte Nuclear Factor 3-beta