Acetylation by histone acetyltransferase CREB-binding protein/p300 of STAT6 is required for transcriptional activation of the 15-lipoxygenase-1 gene.
Interleukin-4 (IL-4) induces expression of reticulocyte-type 15-lipoxygenase-1 (15-LOX-1) in various mammalian cells via the Janus kinase/signal transducer and activator of transcription 6 (STAT6) signaling system. We studied the mechanism of 15-LOX-1 induction in A549 lung epithelial cells and found that genistein, a potent tyrosine kinase inhibitor, prevented phopsphorylation of STAT6, its binding to the 15-LOX-1 promoter, and the expression of catalytically active enzyme. In contrast, cycloheximide did not prevent 15-LOX-1 induction. Surprisingly, we found that IL-4 up-regulated the histone acetyltransferase activity of CREB-binding protein (CBP)/p300, which is responsible for acetylation of nuclear histones and STAT6. The acetylation of both proteins appears to be essential for the IL-4-induced signal transduction cascade, because inhibition of CBP/p300 by the viral wild-type E1A oncoprotein abrogated acetylation of both histones and STAT6 and strongly suppressed transcriptional activation of the 15-LOX-1 gene. Moreover, we found that the inhibition by sodium butyrate of histone deacetylases, which apparently suppress 15-LOX-1 gene transcription, synergistically enhanced the IL-4-stimulated 15-LOX-1 expression. These data suggest that both phosphorylation and acetylation of STAT6 as well as acetylation of nuclear histones are involved in transcriptional activation of the 15-LOX-1 gene, although these reactions follow differential kinetics. STAT6 phosphorylation proceeds within the first hour of IL-4 stimulation. In contrast, CBP/p300-mediated acetylation requires 9-11 h, and similar kinetics were observed for the expression of the active enzyme. Thus, our results suggest that in the absence of IL-4, nuclear histones may be bound to regulatory elements of the 15-LOX-1 gene, preventing its transcription. IL-4 stimulation causes rapid phosphorylation of STAT6, but its binding to the promoter appears to be prevented by nonacetylated histones. After 9-11 h, when histones become acetylated, STAT6 binding sites may be demasked so that the phosphorylated and acetylated transcription factor can bind to activate gene transcription.
Shankaranarayanan
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P
Eicosanoid Research Division, Department of Gynaecology, University Medical Centre Benjamin Franklin, Free University Berlin, D-12200 Berlin, Germany.
Chaitidis
P
P
Kühn
H
H
Nigam
S
S
D000107:Acetylation; D000123:Acetyltransferases / Q000378:metabolism*; D001093:Arachidonate 15-Lipoxygenase / Q000378:metabolism*; D001665:Binding Sites; D015153:Blotting, Western; D050882:CREB-Binding Protein; D002384:Catalysis; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism; D002843:Chromatin / Q000378:metabolism; D002846:Chromatography, Affinity; D018076:DNA, Complementary / Q000378:metabolism; D004789:Enzyme Activation; D015971:Gene Expression Regulation, Enzymologic; D019833:Genistein / Q000494:pharmacology; D051548:Histone Acetyltransferases; D006657:Histones / Q000378:metabolism; D006801:Humans; D015847:Interleukin-4 / Q000378:metabolism; D007700:Kinetics; D009687:Nuclear Proteins / Q000378:metabolism*; D010766:Phosphorylation; D010957:Plasmids / Q000378:metabolism; D011233:Precipitin Tests; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors; D050800:STAT6 Transcription Factor; D029701:Saccharomyces cerevisiae Proteins; D015398:Signal Transduction; D013997:Time Factors; D015534:Trans-Activators / Q000378:metabolism*; D014158:Transcription, Genetic; D015533:Transcriptional Activation; D014162:Transfection; D015854:Up-Regulation
D002843:Chromatin; D018076:DNA, Complementary; D006657:Histones; D009687:Nuclear Proteins; D050800:STAT6 Transcription Factor; C494101:STAT6 protein, human; D029701:Saccharomyces cerevisiae Proteins; D015534:Trans-Activators; D015847:Interleukin-4; D019833:Genistein; D001093:Arachidonate 15-Lipoxygenase; D000123:Acetyltransferases; D050882:CREB-Binding Protein; C494363:CREBBP protein, human; D051548:Histone Acetyltransferases; D011505:Protein-Tyrosine Kinases