Regulation of human IP-10 gene expression in astrocytoma cells by inflammatory cytokines.
Because of its prominent expression in central nervous system inflammatory pathology by astrocytes, we examined the mechanism of human IP-10 (hIP-10) gene induction by interferon-gamma (IFN-gamma) and tumor necrosis factor-alpha (TNF-alpha) in astrocytoma cells. When present together, IFN-gamma and TNF-alpha induced robust accumulation of hIP-10 mRNA, but hIP-10 mRNA was minimally induced when astrocytoma cells were treated with individual cytokines. This pattern of expression resembled that previously described for murine IP-10 (mIP-10) gene induction in fibroblasts and in rat astroglia. Nuclear run-on experiments showed that the synergistic effect of the cytokines resulted from an increased rate of IP-10 transcriptional initiation. Functional analysis of the hIP-10 promoter after deletion and substitution mutagenesis indicated that an interferon-stimulated response element (ISRE) governed both simple response to IFN-gamma and synergy with TNF-alpha. Synergistic induction of hIP-10 also required an ISRE-proximal nuclear factor kappa-B (NFkappaB) binding site. TNF-alpha-induced NFkappaB binding activity at this site was composed of RelA (p65) homodimers. Our results document that cis-elements through which cytokines mediate synergistic induction of IP-10 in mouse and human are strictly conserved despite divergence elsewhere within the proximal 5'-flanking region.
Majumder
S
S
Department of Neurosciences, Lerner Research Institute, Cleveland Clinic Foundation, Ohio 44195, USA.
Zhou
L Z
LZ
Chaturvedi
P
P
Babcock
G
G
Aras
S
S
Ransohoff
R M
RM
D000818:Animals; D001254:Astrocytoma / Q000378:metabolism*; D001665:Binding Sites; D004357:Drug Synergism; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects*; D015894:Genome, Human; D006801:Humans; D007371:Interferon-gamma / Q000494:pharmacology*; D051379:Mice; D016328:NF-kappa B / Q000378:metabolism; D051381:Rats; D014158:Transcription, Genetic / Q000187:drug effects; D015533:Transcriptional Activation; D014407:Tumor Cells, Cultured; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*
D016328:NF-kappa B; D014409:Tumor Necrosis Factor-alpha; D007371:Interferon-gamma