MEMBERS OF THE HNF-3 FORKHEAD FAMILY OF TRANSCRIPTION FACTORS EXHIBITDISTINCT CELLULAR EXPRESSION PATTERNS IN LUNG AND REGULATE THE SURFACTANT PROTEIN-B PROMOTER

The hepatocyte nuclear factor 3 (HNF-3)/fork head (fkh) proteins consi st of an extensive family of tissue-specific and developmental gene re gulators which share homology within the winged helix DNA binding moti f. We report on the isolation of a new family member, HNF-3/forkhead h omolog 8 (HFH-8), from lung cDNA libraries and the derivation of the c omplete amino acid sequences for the HFH-8 protein as well as previous ly identified HFH-1 and HFH-4 proteins. The HFH proteins contain sever al sequence motifs found in activation domains of other transcription factors and HNF-3/fkh family members. In situ hybridization with the H NF-3, HFH-4, and HFH-8 probes in adult lung demonstrate that the HNF-3 /fkh cellular expression patterns are regionally specified. Whereas HN F-3 alpha and HNF-3 beta are normally coexpressed in the hepatocyte, t heir expression patterns in the lung are different. The HNF-3 alpha an d HFH-4 genes are coexpressed in the bronchiolar epithelium (clara cel ls), whereas the HNF-3 beta probe exhibits prominent hybridization wit h the smooth muscle surrounding arterioles and bronchioles. In contras t, HFH-8 probes labeled the type II pneumocyte cells lining the respir atory surfaces of terminal bronchioles and alveolar sac. We have ident ified an HNF-3 consensus DNA binding sequence in the proximal surfacta nt protein B (SPB) promoter region (SPB-f2, -78 to -88). SPB gene tran scription is restricted to bronchiolar and alveolar epithelium which c olocalizes with the expression pattern of the HNF-3 alpha and HFH-8 ge nes, respectively. We show that the SPB-f2 sequence is recognized by b oth HNF-3 alpha and HFH-8 proteins and that these cDNA expression vect ors 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. (C) 1994 Academic Press, Inc.