TNF and CD95 promote IL-8 gene transactivation via independent elements in colon carcinoma cells.
The pro-inflammatory cytokine interleukin-8 (IL-8) is produced by HT29 colon epithelial cells following engagement of either CD95 or tumour necrosis factor (TNF) receptors. While the IL-8 promotor elements activated by TNF are well characterised, those responsible for induction of IL-8 by CD95 are unknown. We examined the pathway for CD95 induced IL-8 secretion using two luciferase reporter constructs; the first comprising approximately 500 bp of the IL-8 promotor that includes the nuclear factor kappa B (NFkappaB), C/EBP and AP-1 sites known to be involved in TNF mediated IL-8 induction; the second that encompasses these elements but extends approximately 1.1 kb further upstream. Although IL-8 mRNA and protein were produced in response to either TNF or CD95 ligation, only TNF induced an increase in the reporter activity of the promoter constructs. Nevertheless, IL-8 induction by CD95 resulted primarily from increased transcription and not from an increase in IL-8 mRNA stability. These results suggest that promoter elements/enhancers involved in CD95 mediated IL-8 induction are distinct from those used by TNF and not contained within the 1.6 kb region immediately upstream of the initiation codon.
Verhagen
A M
AM
The Walter and Eliza Hall Institute of Medical Research, Post Office Royal Melbourne Hospital, Victoria 3050, Australia. verhagen@wehi.edu.au
Pakusch
M
M
Silke
J
J
Vaux
D L
DL
D003106:Colon / Q000378:metabolism; D003110:Colonic Neoplasms / Q000235:genetics / Q000378:metabolism*; D019073:HT29 Cells; D006801:Humans; D007371:Interferon-gamma; D016209:Interleukin-8 / Q000819:agonists / Q000235:genetics* / Q000378:metabolism*; D007413:Intestinal Mucosa / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D018124:Receptors, Tumor Necrosis Factor / Q000276:immunology / Q000378:metabolism*; D015398:Signal Transduction; D015533:Transcriptional Activation / Q000187:drug effects / Q000276:immunology; D014409:Tumor Necrosis Factor-alpha / Q000276:immunology / Q000378:metabolism* / Q000494:pharmacology; D019014:fas Receptor / Q000276:immunology / Q000378:metabolism* / Q000494:pharmacology
D016209:Interleukin-8; D012333:RNA, Messenger; D018124:Receptors, Tumor Necrosis Factor; D014409:Tumor Necrosis Factor-alpha; D019014:fas Receptor; D007371:Interferon-gamma