Activation of the human aldehyde oxidase (hAOX1) promoter by tandem cooperative Sp1/Sp3 binding sites: identification of complex architecture in the hAOX upstream DNA that includes a proximal promoter, distal activation sites, and a silencer element.
Aldehyde oxidase (AOX) is a member of the molybdenum iron-sulfur flavoproteins and is of interest for its role in clinical drug metabolism and as a source of reactive oxygen species (ROS) potentially involved in human pathology. The ROS derived from AOX contribute significantly to alcohol-induced hepatotoxicity. Therefore, expression of AOX could determine both the susceptibility of certain cells and tissues to clinically important pharmacologic agents and the levels of ROS produced under certain pathophysiological conditions. Although some pharmacologic agents regulate AOX enzyme activity, very little is known about the activation or regulation of the human AOX gene (hAOX). In the present study, we sought to identify features in the upstream DNA of hAOX that could confer regulation of the gene, to locate and characterize the basal promoter apparatus activating hAOX, and to identify transcription factors that could mediate activation or regulation. We transfected promoter fusion constructs into epithelial cells from the lung and the mammary gland that express AOX in cell culture. The hAOX gene was found to possess a structurally complex region in the upstream DNA that contained sequences for a proximal promoter, enhancer sites, and silencer elements. In addition, we identified an essential role for the transcription factors Sp1 and Sp3 in the proximal promoter. Unexpectedly, hAOX was activated in lung and mammary epithelial cells by indistinguishable mechanisms. These observations reveal a potentially complex mode of hAOX gene expression in epithelial cells that is dependent on Spl and Sp3 transcription factors.
Wright
R M
RM
The Webb-Waring Institute and Department of Medicine, The University of Colorado Health Sciences Center, Denver 80262, USA. richard.m.wright@uchse.edu
Riley
M G
MG
Weigel
L K
LK
Ginger
L A
LA
Costantino
D A
DA
McManaman
J L
JL
D042931:Aldehyde Oxidase; D000445:Aldehyde Oxidoreductases / Q000235:genetics*; D001483:Base Sequence; D001665:Binding Sites; D004268:DNA-Binding Proteins / Q000378:metabolism*; D005420:Flavoproteins / Q000235:genetics; D015971:Gene Expression Regulation, Enzymologic; D020868:Gene Silencing; D006801:Humans; D007506:Iron-Sulfur Proteins / Q000235:genetics; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D011993:Recombinant Fusion Proteins; D017422:Sequence Analysis, DNA; D016329:Sp1 Transcription Factor / Q000378:metabolism*; D051705:Sp3 Transcription Factor; D014157:Transcription Factors / Q000378:metabolism*; D015533:Transcriptional Activation
D004268:DNA-Binding Proteins; D005420:Flavoproteins; D007506:Iron-Sulfur Proteins; D011993:Recombinant Fusion Proteins; C497121:SP3 protein, human; D016329:Sp1 Transcription Factor; D014157:Transcription Factors; D051705:Sp3 Transcription Factor; D000445:Aldehyde Oxidoreductases; D042931:Aldehyde Oxidase