Mechanism of interleukin-1- and tumor necrosis factor alpha-dependent regulation of the alpha 1-antichymotrypsin gene in human astrocytes.
The expression of alpha(1)-antichymotrypsin (ACT) is significantly enhanced in affected brain regions in Alzheimer's disease. This serine proteinase inhibitor specifically colocalizes with filamentous beta-amyloid deposits and recently has been shown to influence both formation and destabilization of beta-amyloid fibrils. In the brain, ACT is expressed in astrocytes, and interleukin-1 (IL-1), tumor necrosis factor alpha (TNF), oncostatin M (OSM), and IL-6/soluble IL-6 receptor complexes control synthesis of this inhibitor. Here, we characterize a molecular mechanism responsible for both IL-1 and TNF-induced expression of ACT gene in astrocytes. We identify the 5' distal IL-1/TNF-responsive enhancer of the ACT gene located 13 kb upstream of the transcription start site. This 413-bp-long enhancer contains three elements, two of which bind nuclear factor kB (NF-kB) and one that binds activating protein 1 (AP-1). All of these elements contribute to the full responsiveness of the ACT gene to both cytokines, as determined by deletion and mutational analysis. The 5' NF-kB high-affinity binding site and AP-1 element contribute most to the enhancement of gene transcription in response to TNF and IL-1. In addition, we demonstrate that the 5' untranslated region of the ACT mRNA does not contribute to cytokine-mediated activation. Finally, we find that overexpression of the NF-kB inhibitor (IkB) totally inhibits any activation mediated by the newly identified IL-1/TNF enhancer of the ACT gene.
Kordula
T
T
Institute of Molecular Biology, Jagiellonian University, 31-120 Kraków, Poland.
Bugno
M
M
Rydel
R E
RE
Travis
J
J
D020121:5' Untranslated Regions / Q000235:genetics; D000544:Alzheimer Disease / Q000378:metabolism; D001253:Astrocytes / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D001665:Binding Sites / Q000235:genetics; D002478:Cells, Cultured; D004742:Enhancer Elements, Genetic; D005786:Gene Expression Regulation / Q000187:drug effects*; D006801:Humans; D007375:Interleukin-1 / Q000378:metabolism* / Q000494:pharmacology; D016297:Mutagenesis, Site-Directed; D016328:NF-kappa B / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D017422:Sequence Analysis, DNA; D018808:Transcription Factor AP-1 / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism* / Q000494:pharmacology; D015854:Up-Regulation; D000514:alpha 1-Antichymotrypsin / Q000235:genetics / Q000378:metabolism*
D020121:5' Untranslated Regions; D007375:Interleukin-1; D016328:NF-kappa B; D012333:RNA, Messenger; D018808:Transcription Factor AP-1; D014409:Tumor Necrosis Factor-alpha; D000514:alpha 1-Antichymotrypsin