Differential activation of lung-specific genes by two forkhead proteins, FREAC-1 and FREAC-2.
We describe the cDNA sequences for two human transcription factors, Forkhead RElated ACtivator (FREAC)-1 and -2, that belong to the forkhead family of eukaryotic DNA binding proteins. FREAC-1 and -2 are encoded by distinct genes, are almost identical within their DNA binding domains and in the COOH termini, but are otherwise divergent. Cotransfections with a reporter carrying FREAC binding sites showed that both proteins are transcriptional activators, and deletions located the activation domains to the COOH-terminal side of the forkhead domains. Expression of FREAC-1 and FREAC-2 is restricted to lung and placenta. We show that the promoters of genes for lung-specific proteins such as pulmonary surfactant proteins A, B, and C (SPA, SPB, and SPC) and the Clara cell 10-kDa protein (CC10) contain potential binding sites for FREAC-1 and FREAC-2. DNaseI footprinting verified that FREAC proteins bind to the predicted sites in the CC10 and SPB promoters. While an SPB promoter construct could be transactivated by both FREAC-1 and FREAC-2, CC10 was only activated by FREAC-1. Efficient activation of CC10 by FREAC-1 is shown to be specific for a lung cell line with Clara cell characteristics (H441) and to involve a region of the FREAC-1 protein unable to activate in other cell types.
Hellqvist
M
M
Department of Molecular Biology, The Lundberg Laboratory, Göteborg University, Medicinaregatan 9C, S-413 90 Göteborg, Sweden.
Mahlapuu
M
M
Samuelsson
L
L
Enerbäck
S
S
Carlsson
P
P
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D002460:Cell Line; D003001:Cloning, Molecular; D004268:DNA-Binding Proteins / Q000096:biosynthesis* / Q000378:metabolism; D005260:Female; D051858:Forkhead Transcription Factors; D005786:Gene Expression Regulation; D015723:Gene Library; D006801:Humans; D007301:Insect Hormones / Q000096:biosynthesis; D008156:Luciferases / Q000096:biosynthesis; D008168:Lung / Q000378:metabolism*; D051379:Mice; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009687:Nuclear Proteins / Q000096:biosynthesis; D010920:Placenta / Q000378:metabolism; D011247:Pregnancy; D011401:Promoter Regions, Genetic; D011817:Rabbits; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis; D012689:Sequence Homology, Nucleic Acid; D015534:Trans-Activators / Q000096:biosynthesis* / Q000378:metabolism; D014157:Transcription Factors / Q000096:biosynthesis* / Q000378:metabolism
D004268:DNA-Binding Proteins; C098521:FOXF1 protein, human; C486413:FOXF2 protein, human; D051858:Forkhead Transcription Factors; C486293:Foxf1 protein, mouse; C486412:Foxf2 protein, mouse; D007301:Insect Hormones; C114562:LUN protein, vertebrate; D009687:Nuclear Proteins; D011993:Recombinant Fusion Proteins; D015534:Trans-Activators; D014157:Transcription Factors; D008156:Luciferases