1alpha-Hydroxylase transactivation by gamma-interferon in murine macrophages requires enhanced C/EBPbeta expression and activation.
gamma-Interferon [gamma-IFN] induction of macrophage 1alpha-hydroxylase mRNA and activity causes severe hypercalcemia in granulomatous disorders. These studies demonstrate transcriptional regulation. gamma-IFN induces the activity of the murine 1alpha-hydroxylase [-1651; +22] promoter in the murine macrophage cell line Raw 264.7 only after a 24h exposure. This slow kinetics is incompatible with classical gamma-IFN-mediated transactivation. In fact, gamma-IFN response mapped to the minimal [-85; +11] promoter, which lacks GAS or ISRE sites but contains a putative C/EBPbeta site. C/EBPbeta is a gamma-IFN inducible gene and a novel mediator of gamma-IFN-regulated transcription. As expected for a C/EBPbeta-driven transcription, ectopic C/EBPbeta expression was sufficient to increase 1alpha-hydroxylase activity, enhance minimal promoter activity and potentiate the induction of this promoter by gamma-IFN. Importantly, the dominant negative C/EBPbeta isoform antagonized C/EBPbeta-transcriptional activity. gamma-IFN induction of C/EBPbeta expression is not sufficient for gamma-IFN induction of minimal promoter activity. There is also a cell-specific induction of C/EBPbeta-transcriptional activity by gamma-IFN. In Raw cells, specific inhibition of gamma-IFN induction of endogenous-C/EBPbeta phosphorylation by MEKK1 markedly reduced basal promoter activity and the response to gamma-IFN. We conclude that gamma-IFN-induction of C/EBPbeta expression and activation by phosphorylation contributes to gamma-IFN-transcriptional control of 1alpha-hydroxylase expression in murine macrophages.
Esteban
L
L
Department of Internal Medicine, Washington University School of Medicine, Campus Box 8126, 660 S. Euclid Avenue, St. Louis, MO 63110, USA.
Vidal
M
M
Dusso
A
A
D000818:Animals; D001483:Base Sequence; D022782:CCAAT-Enhancer-Binding Protein-beta / Q000235:genetics*; D002460:Cell Line; D004247:DNA / Q000235:genetics; D007371:Interferon-gamma / Q000494:pharmacology*; D008264:Macrophages / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism; D051379:Mice; D012333:RNA, Messenger / Q000235:genetics; D013250:Steroid Hydroxylases / Q000235:genetics*; D015533:Transcriptional Activation / Q000187:drug effects*
D022782:CCAAT-Enhancer-Binding Protein-beta; D012333:RNA, Messenger; D007371:Interferon-gamma; D004247:DNA; D013250:Steroid Hydroxylases