Rapamycin destabilizes interleukin-3 mRNA in autocrine tumor cells by a mechanism requiring an intact 3' untranslated region.
We analyzed the effect of rapamycin on autocrine mast cell tumor lines with abnormally stable interleukin-3 (IL-3) transcripts due to a defect in mRNA degradation. Rapamycin inhibited IL-3 mRNA expression specifically, while transcripts of IL-4 and IL-6 were not affected. As indicated by the use of the transcriptional inhibitor actinomycin D or by reporter constructs, inhibition was posttranscriptional and resulted from destabilization of the mRNA. Transcripts from transgenes lacking the AU-rich 3' untranslated region were refractory to drug-induced degradation, suggesting that these 3' sequences contain the target of the rapamycin effect. Rapamycin did not promote IL-3 mRNA degradation in cells of a tumor variant lacking expression of FKBP12, the binding protein of rapamycin. Experiments with wortmannin indicated that rapamycin does not act via p70S6 kinase. FK-506, another ligand of FKBP12 affecting the phosphatase calcineurin, did not antagonize but shared the effect of rapamycin. Our data fit a model whereby both FKBP12 and calcineurin target an unknown regulator of IL-3 mRNA turnover.
Banholzer
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Institute for Medical Microbiology, University of Basel, Switzerland.
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Hirsch
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Ming
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Moroni
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D000591:Amino Acid Isomerases / Q000378:metabolism; D000818:Animals; D000903:Antibiotics, Antineoplastic / Q000378:metabolism* / Q000494:pharmacology; D001665:Binding Sites; D002352:Carrier Proteins / Q000378:metabolism; D002455:Cell Division / Q000187:drug effects; D016572:Cyclosporine / Q000494:pharmacology; D004268:DNA-Binding Proteins / Q000378:metabolism; D015536:Down-Regulation / Q000187:drug effects; D006360:Heat-Shock Proteins / Q000378:metabolism; D007166:Immunosuppressive Agents / Q000494:pharmacology; D007377:Interleukin-3 / Q000235:genetics*; D051379:Mice; D011090:Polyenes / Q000378:metabolism* / Q000494:pharmacology; D011499:Protein Processing, Post-Translational; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors; D012333:RNA, Messenger / Q000378:metabolism*; D019893:Ribosomal Protein S6 Kinases; D020123:Sirolimus; D016559:Tacrolimus / Q000494:pharmacology; D022021:Tacrolimus Binding Proteins; D014407:Tumor Cells, Cultured
D000903:Antibiotics, Antineoplastic; D002352:Carrier Proteins; D004268:DNA-Binding Proteins; D006360:Heat-Shock Proteins; D007166:Immunosuppressive Agents; D007377:Interleukin-3; D011090:Polyenes; D012333:RNA, Messenger; D016572:Cyclosporine; D017346:Protein Serine-Threonine Kinases; D019893:Ribosomal Protein S6 Kinases; D000591:Amino Acid Isomerases; D022021:Tacrolimus Binding Proteins; D020123:Sirolimus; D016559:Tacrolimus