BR22, a novel protein, interacts with thyroid transcription factor-1 and activates the human surfactant protein B promoter.
Surfactant protein (SP)-B expression is restricted to type II pneumocytes and Clara cells in the lung. Previously, a promoter region of human SP-B gene from -64 to -118 has been identified as critical for the tissue-specific expression of this gene. Two cis-elements for thyroid transcription factor (TTF)-1 and hepatocyte nuclear factor (HNF)-3alpha binding were found within this area. Using an oligonucleotide fragment, we incorporated this region sequence into the promoter of a HIS3 reporter gene in yeast. With this modified yeast a human lung complementary DNA (cDNA) library was screened for DNA-binding proteins, other than TTF-1 and HNF-3alpha, that interacted with this promoter segment. A cDNA clone encoding a novel polypeptide, BR22, was identified that activated the reporter gene expression in yeast. This gene is expressed in many tissues and encodes a protein with bipartite nuclear localization signals. Studies using in vivo yeast two-hybrid analysis, in vitro protein-protein interactions, and coimmunoprecipitation analyses demonstrated that BR22 formed a protein complex with TTF-1. In vivo cotransfection studies further indicated that BR22 could act with TTF-1 to synergistically activate the SP-B promoter in mammalian cells. Our data suggest that BR22 is a TTF-1-associated protein. Through a protein-protein interaction with TTF-1, BR22 can form a complex and activate the human SP-B promoter in vivo.
Yang
Y S
YS
Department of Internal Medicine, Pulmonary and Critical Care Medicine, UT Southwestern Medical Center, Dallas, Texas 75390-9034, USA. Yih-Shing.Yang@UTSouthwestern.edu.
Yang
M C
MC
Wang
B
B
Weissler
J C
JC
D000595:Amino Acid Sequence; D001483:Base Sequence; D001665:Binding Sites / Q000235:genetics; D015723:Gene Library; D017930:Genes, Reporter; D006801:Humans; D008168:Lung; D009687:Nuclear Proteins / Q000235:genetics* / Q000378:metabolism*; D009928:Organ Specificity / Q000235:genetics; D011233:Precipitin Tests; D011401:Promoter Regions, Genetic / Q000235:genetics*; D011485:Protein Binding / Q000235:genetics; D011510:Proteolipids / Q000235:genetics* / Q000378:metabolism; D011663:Pulmonary Surfactants / Q000235:genetics* / Q000378:metabolism; D012045:Regulatory Sequences, Nucleic Acid / Q000235:genetics; D017386:Sequence Homology, Amino Acid; D000074482:Thyroid Nuclear Factor 1; D014157:Transcription Factors / Q000378:metabolism*; D015533:Transcriptional Activation / Q000235:genetics; D014162:Transfection; D020798:Two-Hybrid System Techniques
C511144:CCDC59 protein, human; C000614412:NKX2-1 protein, human; D009687:Nuclear Proteins; D011510:Proteolipids; D011663:Pulmonary Surfactants; D000074482:Thyroid Nuclear Factor 1; D014157:Transcription Factors