Transcriptional and post-transcriptional regulation of interleukin-8.
Steady-state mRNA for interleukin (IL) 8 persists significantly longer than mRNA for tumor necrosis factor (TNF)-alpha in lipopolysaccharide (LPS) stimulated human whole blood. Nuclear run-ons demonstrated consistent levels of transcriptional activity of the IL-8 gene at 2 and 26 hours after LPS stimulation when compared with the rapid induction and arrest of the TNF-alpha gene. Inhibition of cellular transcription with actinomycin D added at 2 hours after LPS resulted in the substantial decrease of both IL-8 and TNF-alpha mRNAs, demonstrating half-lives of 4.6 and 2.3 hours, respectively. In contrast, inhibition of transcription at 23 hours after LPS revealed extremely stable IL-8 mRNA with a half-life of > 10 hours. The half-life of beta-actin in the same actinomycin-D-treated samples did not vary significantly from the half-life calculated at the 2-hour time point (5.5 hours versus 5.6 hours), indicating that the observed IL-8 mRNA stability was not an artifact of the system. Both IL-8 and TNF-alpha protein levels decreased when actinomycin D was added 2 hours after LPS stimulation. However, no effect in IL-8 protein levels was evident when actinomycin D was added at 23 hours after LPS. These results demonstrate that IL-8 mRNA stability is controlled at both the transcriptional and posttranscriptional levels of gene regulation.
Department of Pathology, University of Michigan Medical School, Ann Arbor, USA.
L H
LH
Villarete
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DG
Remick
D006801:Humans; D016209:Interleukin-8 / Q000235:genetics* / Q000378:metabolism; D012323:RNA Processing, Post-Transcriptional; D012333:RNA, Messenger / Q000378:metabolism; D014158:Transcription, Genetic; D014409:Tumor Necrosis Factor-alpha / Q000235:genetics
D016209:Interleukin-8; D012333:RNA, Messenger; D014409:Tumor Necrosis Factor-alpha