Overexpression of CCAAT displacement protein represses the promiscuously active proximal gp91(phox) promoter.
CCAAT displacement protein (CDP) is a transcriptional repressor that restricts expression of the gp91(phox) gene to mature myeloid cells. CDP interacts with multiple sites within the -450 to +12 bp human gp91(phox) promoter, and down-regulation of CDP DNA-binding activity is required for induction of gp91(phox) transcription in mature phagocytes. Truncation of the gp91(phox) promoter to -102 to +12 bp removes 4 CDP-binding sites and reveals a promiscuous promoter activity that is active in some nonphagocytic cells. A cis-element at -90 bp is required for derepressed transcription and serves as a binding site for multiple transcriptional activators. We now report that this element also serves as a binding site for CDP. The affinity of CDP for this element is relatively weak compared with upstream CDP-binding sites within the promoter, consistent with the promiscuous transcriptional activity exhibited by the -102 to +12 bp gp91(phox) promoter fragment. Further analysis of the proximal promoter reveals an additional weak-affinity CDP-binding site centered at approximately -20 bp. Overexpression of cloned CDP represses the -102 to +12 bp gp91(phox) promoter, indicating that these proximal CDP-binding sites are functionally significant. The constellation of transcriptional activators and a repressor that interacts with the -90 bp cis-element is identical to that observed for a promoter element at -220 bp, reflecting the highly modular organization of the gp91(phox) promoter. These studies illustrate the complex interplay between transcriptional activators and a repressor that contribute to the myeloid-restricted expression of the gp91(phox) gene.
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Departments of Pediatrics, Biochemistry & Molecular Biology, Section of Pediatric Hematology/Oncology, Herman B Wells Center for Pediatric Research, Indiana University School of Medicine and Walther Cancer Institute, Indianapolis 46202, USA.
Hawkins
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Roman
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Luo
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Skalnik
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D002454:Cell Differentiation / Q000235:genetics; D005786:Gene Expression Regulation; D006367:HeLa Cells; D018398:Homeodomain Proteins / Q000235:genetics; D006801:Humans; D008562:Membrane Glycoproteins / Q000235:genetics*; D000074662:NADPH Oxidase 2; D019255:NADPH Oxidases; D009687:Nuclear Proteins / Q000235:genetics*; D011401:Promoter Regions, Genetic / Q000235:genetics; D012097:Repressor Proteins / Q000235:genetics*; D014157:Transcription Factors; D014158:Transcription, Genetic
C080632:CUX1 protein, human; D018398:Homeodomain Proteins; D008562:Membrane Glycoproteins; D009687:Nuclear Proteins; D012097:Repressor Proteins; D014157:Transcription Factors; C056558:CYBB protein, human; D000074662:NADPH Oxidase 2; D019255:NADPH Oxidases