Members of the HNF-3/forkhead family of transcription factors exhibit distinct cellular expression patterns in lung and regulate the surfactant protein B promoter.
The hepatocyte nuclear factor-3 (HNF-3)/forkhead (fkh) proteins consist of an extensive family of tissue-specific and developmental gene regulators which share homology within the winged helix DNA binding motif. We report on the isolation of a new family member, HNF-3/forkhead homolog 8 (HFH-8), from lung cDNA libraries and the derivation of the complete amino acid sequences for the HFH-8 protein as well as previously identified HFH-1 and HFH-4 proteins. The HFH proteins contain several sequence motifs found in activation domains of other transcription factors and HNF-3/fkh family members. In situ hybridization with the HNF-3, HFH-4, and HFH-8 probes in adult lung demonstrate that the HNF-3/fkh cellular expression patterns are regionally specified. Whereas HNF-3 alpha and HNF-3 beta are normally coexpressed in the hepatocyte, their expression patterns in the lung are different. The HNF-3 alpha and HFH-4 genes are coexpressed in the bronchiolar epithelium (clara cells), whereas the HNF-3 beta probe exhibits prominent hybridization with the smooth muscle surrounding arterioles and bronchioles. In contrast, HFH-8 probes labeled the type II pneumocyte cells lining the respiratory surfaces of terminal bronchioles and alveolar sac. We have identified an HNF-3 consensus DNA binding sequence in the proximal surfactant protein B (SPB) promoter region (SPB-f2, -78 to -88). SPB gene transcription is restricted to bronchiolar and alveolar epithelium which colocalizes with the expression pattern of the HNF-3 alpha and HFH-8 genes, respectively. We show that the SPB-f2 sequence is recognized by both HNF-3 alpha and HFH-8 proteins and that these cDNA expression vectors activate the SPB promoter in cotransfection assays through the HNF-3 consensus sequence. Our results suggest that SPB promoter activity is regulated by HNF-3 alpha and HFH-8 proteins in a cell type-specific manner.
Department of Biochemistry (M/C 536), College of Medicine, University of Illinois at Chicago 60612-7334.
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Clevidence
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Overdier
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Peterson
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A
Porcella
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Ye
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Paulson
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Costa
D000375:Aging / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001980:Bronchi / Q000378:metabolism; D005314:Embryonic and Fetal Development; D004848:Epithelium / Q000378:metabolism; D051858:Forkhead Transcription Factors; D015870:Gene Expression; D005786:Gene Expression Regulation; D015723:Gene Library; D017403:In Situ Hybridization; D008099:Liver / Q000378:metabolism; D008168:Lung / Q000166:cytology / Q000378:metabolism*; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000096:biosynthesis* / Q000378:metabolism; D009928:Organ Specificity; D011401:Promoter Regions, Genetic; D011510:Proteolipids / Q000096:biosynthesis*; D011650:Pulmonary Alveoli / Q000378:metabolism; D011663:Pulmonary Surfactants / Q000096:biosynthesis*; D051381:Rats; D017207:Rats, Sprague-Dawley; D011993:Recombinant Fusion Proteins; D017386:Sequence Homology, Amino Acid; D014157:Transcription Factors / Q000096:biosynthesis* / Q000378:metabolism
D051858:Forkhead Transcription Factors; D009687:Nuclear Proteins; D011510:Proteolipids; D011663:Pulmonary Surfactants; D011993:Recombinant Fusion Proteins; D014157:Transcription Factors