Involvement of Sp1 elements in the promoter activity of the alpha1-proteinase inhibitor gene.
The transcripts of the alpha1-proteinase inhibitor in the cornea are different from those in hepatocytes and monocytes, suggesting that alpha1-proteinase inhibitor gene transcription may respond to different cell-specific regulatory mechanisms. Although information on alpha1-proteinase inhibitor gene structure has been obtained, little is known regarding the cis- and trans-acting factors that regulate its expression. In this study, we cloned and sequenced a 2. 7-kilobase 5'-flanking region upstream from the corneal transcription initiation site of the gene, demonstrated functional promoter activity, and identified the regulatory elements. Sequencing revealed that the 5'-flanking element was highly G/C-rich in regions proximal to the corneal transcription start site. DNase I footprinting located 10 potential Sp1-binding sites between nucleotides -1519 and +44. The putative promoter was functional in human corneal stromal cells, but not in human skin, scleral, and conjunctival fibroblasts, suggesting that the promoter may be corneal cell-specific. The promoter activity in the corneal cells was repressed when Sp1 was coexpressed. In the cornea-thinning disease keratoconus, down-regulation of the alpha1-proteinase inhibitor gene and increased Sp1 expression have both been demonstrated. The current results suggest that down-regulation of the inhibitor in keratoconus corneas may be related directly to overexpression of the Sp1 gene. This information may help elucidate the molecular pathways leading to the altered alpha1-proteinase inhibitor expression in keratoconus.
Li
Y
Y
Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago College of Medicine, Chicago, Illinois 60612, USA.
Zhou
L
L
Twining
S S
SS
Sugar
J
J
Yue
B Y
BY
D001483:Base Sequence; D002478:Cells, Cultured; D003001:Cloning, Molecular; D003315:Cornea / Q000166:cytology / Q000378:metabolism*; D018983:DNA Footprinting; D003850:Deoxyribonuclease I; D005091:Exons; D005786:Gene Expression Regulation; D006801:Humans; D008099:Liver / Q000378:metabolism; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic; D012867:Skin / Q000378:metabolism; D016329:Sp1 Transcription Factor / Q000378:metabolism*; D017154:Stromal Cells / Q000378:metabolism; D014158:Transcription, Genetic; D000515:alpha 1-Antitrypsin / Q000096:biosynthesis* / Q000235:genetics*
D016329:Sp1 Transcription Factor; D000515:alpha 1-Antitrypsin; D003850:Deoxyribonuclease I