title: Superinduction of interleukin-6 mRNA in lung epithelial H292 cells depends on transiently increased C/EBP activity and durable increased mRNA stability.
abstract: Restriction of eukaryotic protein synthesis affects the regulation of some transiently expressed gene transcripts resulting in their superinduction. We determined the transcriptional and post-transcriptional processes implicated in IL-6 mRNA superinduction in a human lung-derived epithelial cell line H292, and their kinetics in the absence and presence of an exogenous stimulus, tumor necrosis factor-alpha (TNF-alpha). Cycloheximide (CHI) at 10 microg/ml, which inhibited protein synthesis for 80%, caused a 80-fold induction of IL-6 mRNA level which was due predominantly to a stabilization of IL-6 mRNA (20-fold) early on. Employing transient transfection protocols we noted a small positive effect of CHI on transcription, mediated by the proximal and the distal C/EBP sites of the IL-6 promoter and paralleled by an increased C/EBP DNA-binding activity, similar to that found for exposure to TNF-alpha alone. TNF-alpha and CHI synergized on IL-6 mRNA expression (200-fold increase) which was due to an increased transcription, corresponding to a further increased C/EBP DNA-binding activity. However, the effect of CHI on IL-6 gene transcription was transient, in support of the need for ongoing protein synthesis for C/EBP activity. These findings indicate that IL-6 mRNA superinduction, at least in H292 cells, is regulated predominantly by modulating the repressive system that ensures a rapid degradation of IL-6 mRNA.
authors.affiliation: Department of Pulmonology, Academic Medical Center, University of Amsterdam, Meibergdreef 9, P.O. Box 22700, 1100 DE Amsterdam, The Netherlands.
authors.forename: T
authors.initials: T
authors.lastname: Roger
authors.forename: T A
authors.initials: TA
authors.lastname: Out
authors.forename: H M
authors.initials: HM
authors.lastname: Jansen
authors.forename: R
authors.initials: R
authors.lastname: Lutter
mesh_terms: D022762:CCAAT-Enhancer-Binding Proteins; D002467:Cell Nucleus / Q000378:metabolism; D003513:Cycloheximide / Q000494:pharmacology; D004268:DNA-Binding Proteins / Q000378:metabolism*; D004847:Epithelial Cells / Q000378:metabolism; D005786:Gene Expression Regulation / Q000187:drug effects; D006801:Humans; D015850:Interleukin-6 / Q000235:genetics*; D008168:Lung / Q000166:cytology / Q000378:metabolism; D009687:Nuclear Proteins / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D012333:RNA, Messenger; D013997:Time Factors; D014157:Transcription Factors / Q000378:metabolism*; D014407:Tumor Cells, Cultured; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
chemical_list: D022762:CCAAT-Enhancer-Binding Proteins; D004268:DNA-Binding Proteins; D015850:Interleukin-6; D009687:Nuclear Proteins; D011500:Protein Synthesis Inhibitors; D012333:RNA, Messenger; D014157:Transcription Factors; D014409:Tumor Necrosis Factor-alpha; D003513:Cycloheximide