Mechanisms regulating the mRNA levels of interleukin-5 and two other coordinately expressed lymphokines in the murine T lymphoma EL4.23.
The mechanisms that regulate the mRNA levels of interleukin-5 (IL-5) were compared with those regulating the mRNA levels of two other coordinately expressed lymphokines in the murine T lymphoma EL4.23. Our results indicate that IL-5 mRNA levels are independently regulated from those of IL-2 and granulocyte-macrophage colony-stimulating factor (GM-CSF) mRNAs. The induction of IL-5 mRNA by phorbol 12-myristate 13-acetate (PMA) stimulation was found to be cyclosporin A-resistant, in contrast to the induction of IL-2 and GM-CSF mRNAs. Although the three lymphokine mRNAs were not detected in unstimulated cells by Northern blot analysis, the GM-CSF gene was found by nuclear run-off analysis to be constitutively transcribed. However, the IL-2 and IL-5 genes were transcriptionally inactive in the absence of PMA stimulation. The induction of IL-5 mRNA by PMA stimulation primarily involved increased transcriptional activity. In contrast, GM-CSF mRNA induction predominantly involved enhanced mRNA stability. Both transcriptional and mRNA stabilization mechanisms appeared to regulate IL-2 mRNA induction. The activation of IL-2 and IL-5 gene transcription was dependent on de novo protein synthesis. Cellular treatment with cycloheximide enhanced IL-2 gene transcription once activation was initiated, implicating the involvement of a labile repressor(s). Furthermore, IL-5 mRNA was more stable than IL-2 and GM-CSF mRNAs. These latter two species were stabilized by cycloheximide, suggesting that a labile mechanism may regulate their degradation.
Naora
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Division of Biochemistry and Molecular Biology, John Curtin School of Medical Research, Australian National University, Canberra.
Young
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D000818:Animals; D003513:Cycloheximide / Q000494:pharmacology; D016572:Cyclosporine / Q000494:pharmacology; D005786:Gene Expression Regulation / Q000187:drug effects; D016178:Granulocyte-Macrophage Colony-Stimulating Factor / Q000235:genetics; D016753:Interleukin-10 / Q000235:genetics; D007376:Interleukin-2 / Q000235:genetics; D015848:Interleukin-5 / Q000235:genetics*; D008222:Lymphokines / Q000235:genetics*; D016399:Lymphoma, T-Cell / Q000378:metabolism*; D051379:Mice; D012333:RNA, Messenger / Q000032:analysis*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014407:Tumor Cells, Cultured
D007376:Interleukin-2; D015848:Interleukin-5; D008222:Lymphokines; D012333:RNA, Messenger; D016753:Interleukin-10; D016178:Granulocyte-Macrophage Colony-Stimulating Factor; D016572:Cyclosporine; D003513:Cycloheximide; D013755:Tetradecanoylphorbol Acetate