The basic helix-loop-helix-zipper transcription factor USF1 regulates expression of the surfactant protein-A gene.
Expression of the rabbit pulmonary surfactant protein A (SP-A) gene is lung-specific, occurs primarily in type II cells, and is developmentally regulated. We previously identified two E-box-like enhancers, termed the distal binding element (DBE) and proximal binding element (PBE), in the 5'-flanking region of the rabbit SP-A gene. In the present study, the PBE was used to screen a rabbit fetal lung cDNA expression library; a cDNA insert was isolated which is highly similar in sequence to human upstream stimulatory factor 1 (hUSF1). By use of reverse transcription polymerase chain reaction, two isoforms of rabbit USF1 (rUSF1) mRNAs were identified in fetal rabbit lung and other tissues. The levels of rUSF1 mRNAs reach a peak in fetal rabbit lung at 23 days gestation, in concert with the time of initiation of SP-A gene transcription. Binding complexes of nuclear proteins obtained from fetal rabbit lung tissue and isolated type II cells with the DBE and PBE were supershifted by the addition of anti-rUSF1 IgG. Binding activity was enriched in type II cells compared with lung fibroblasts. Overexpression of rUSF1s in A549 adenocarcinoma cells positively regulated SP-A promoter activity of cotransfected reporter gene constructs. It is suggested that rUSF1s, which bind to two E-box elements in the SP-A gene 5'-flanking region, may serve a key role in the regulation of SP-A gene expression in pulmonary type II cells.
Gao
E
E
Department of Obstetrics-Gynecology, The University of Texas Southwestern Medical Center at Dallas, Dallas, Texas 75235-9038, USA.
Wang
Y
Y
Alcorn
J L
JL
Mendelson
C R
CR
D000818:Animals; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000235:genetics; D004268:DNA-Binding Proteins; D019281:Dimerization; D004742:Enhancer Elements, Genetic; D018507:Gene Expression Regulation, Developmental; D018257:Helix-Loop-Helix Motifs; D008168:Lung / Q000196:embryology / Q000254:growth & development / Q000502:physiology*; D008969:Molecular Sequence Data; D016133:Polymerase Chain Reaction; D011485:Protein Binding; D011510:Proteolipids / Q000378:metabolism*; D037662:Pulmonary Surfactant-Associated Protein A; D037661:Pulmonary Surfactant-Associated Proteins; D011663:Pulmonary Surfactants / Q000378:metabolism*; D012333:RNA, Messenger / Q000032:analysis; D011817:Rabbits; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis; D012441:Saccharomyces cerevisiae / Q000235:genetics; D017422:Sequence Analysis, DNA; D014018:Tissue Distribution; D014157:Transcription Factors / Q000096:biosynthesis / Q000235:genetics*; D051720:Upstream Stimulatory Factors
D018076:DNA, Complementary; D004268:DNA-Binding Proteins; D011510:Proteolipids; D037662:Pulmonary Surfactant-Associated Protein A; D037661:Pulmonary Surfactant-Associated Proteins; D011663:Pulmonary Surfactants; D012333:RNA, Messenger; D011993:Recombinant Fusion Proteins; D014157:Transcription Factors; D051720:Upstream Stimulatory Factors