Transcriptional and translational control of TNF-alpha gene expression in human monocytes by major histocompatibility complex class II ligands.
While non-stimulated primary human monocytes exhibit very low levels of tumor necrosis factor (TNF)-alpha mRNA, direct binding of the staphylococcal exotoxin toxic shock syndrome toxin-1 (TSST-1) to major histocompatibility complex (MHC) class II molecules results in a fast (peak 1 h after stimulation), transient induction (sevenfold) of TNF-alpha mRNA. This induction correlates with a fourfold increase in transcription rates of the TNF-alpha gene, as detected by run-on assays, and does not require de novo protein synthesis. Mapping of DNase-I hypersensitive sites (DHS) discloses two constitutive DHS, one located far upstream (within the TNF-beta promoter) and the other centered at -39 +/- 40 bp relative to the major TNF-alpha transcription start site, suggesting that the TNF-alpha gene was transcriptionally competent even prior to MHC class II engagement. Furthermore, stimulation of human monocytes with either TSST-1 or lipopolysaccharide increases the translational efficiency of TNF-alpha mRNA, as shown by a shift in the distribution of this mRNA species in polysome gradients and the translation rates of TNF-alpha measured by immunoprecipitation from cells pulsed with [35S] methionine. The increase in translation efficiency of TNF-alpha mRNA is independent of the half-life of TNF-alpha transcripts, which under the conditions used is unchanged. Taken together, our data indicate that TNF-alpha expression is tightly regulated by MHC class II ligands, both at the transcriptional and translational levels.
Department of Medicine, Centre Hospitalier Universitaire Vaudois, Lausanne, Switzerland.
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E
Espel
J A
JA
Garcia-Sanz
V
V
Aubert
V
V
Menoud
P
P
Sperisen
N
N
Fernández
F
F
Spertini
D001427:Bacterial Toxins; D003850:Deoxyribonuclease I; D004768:Enterotoxins / Q000494:pharmacology*; D005786:Gene Expression Regulation / Q000187:drug effects; D000949:Histocompatibility Antigens Class II / Q000502:physiology; D006801:Humans; D008024:Ligands; D008070:Lipopolysaccharides / Q000494:pharmacology; D009000:Monocytes / Q000502:physiology*; D011132:Polyribosomes / Q000378:metabolism; D011401:Promoter Regions, Genetic; D014176:Protein Biosynthesis; D012333:RNA, Messenger / Q000235:genetics; D015398:Signal Transduction; D013211:Staphylococcus aureus / Q000276:immunology; D018089:Superantigens / Q000494:pharmacology; D014158:Transcription, Genetic; D014407:Tumor Cells, Cultured; D014409:Tumor Necrosis Factor-alpha / Q000235:genetics*
D001427:Bacterial Toxins; D004768:Enterotoxins; D000949:Histocompatibility Antigens Class II; D008024:Ligands; D008070:Lipopolysaccharides; D012333:RNA, Messenger; D018089:Superantigens; D014409:Tumor Necrosis Factor-alpha; C030107:enterotoxin F, Staphylococcal; D003850:Deoxyribonuclease I