Transcriptional and posttranscriptional regulation of the interleukin-4 and interleukin-3 genes in human T cells.
Human T cells were studied with regard to the regulation of interleukin-4 (IL-4) and IL-3 gene expression. IL-4 and IL-3 mRNA were undetectable in unstimulated T cells. On activation with the lectin concanavalin A (Con A), both IL-4 and IL-3 mRNA were expressed. Accumulation of IL-4 mRNA peaked after 6 to 12 hours, whereas IL-3 mRNA levels peaked after 3 to 6 hours of stimulation with Con A. Nuclear run-on assays showed a low constitutive transcription for both genes. The transcription rates were increased by Con A resulting in a peak for IL-4 after 1 hour (30% increase) and for IL-3 after 3 hours (40% increase) of Con A treatment. mRNA stability studies demonstrated that on activation with Con A both messages decayed with a half-life of approximately 90 minutes. No IL-4 or IL-3 mRNA expression was induced by the protein kinase C activator phorbol myristate acetate (PMA). However, PMA augmented the Con A-induced IL-4 and IL-3 mRNA accumulation. This was shown to be mediated at posttranscriptional level by a large increase in the stability of both messages (t 1/2 > 3 hours). The transcription rate of both genes was also enhanced by Con A+PMA and reached peak levels for IL-4 after 1 hour (90% increase) and for IL-3 after 3 hours (70% increase) of stimulation. Furthermore, it appeared that the induction of IL-4 mRNA was dependent on protein synthesis because cycloheximide (CHX) blocked the Con A- and Con A+PMA-induced expression of IL-4 mRNA. In contrast, CHX inhibited, but failed to completely block, the Con A- and Con A+PMA-induced IL-3 mRNA expression, whereas the expression of both genes was completely blocked by cyclosporine A. With regard to the secretion of IL-4 protein it was shown that it closely follows the accumulation of IL-4 mRNA. Taken together, the data show that expression of the IL-4 and IL-3 genes in human T cells is controlled by different activation pathways that affect the gene regulation at transcriptional and posttranscriptional levels.
Dokter
W H
WH
Department of Medicine, University of Groningen, The Netherlands.
Esselink
M T
MT
Sierdsema
S J
SJ
Halie
M R
MR
Vellenga
E
E
D015152:Blotting, Northern; D003208:Concanavalin A / Q000494:pharmacology; D003513:Cycloheximide / Q000494:pharmacology; D016572:Cyclosporine / Q000494:pharmacology; D005786:Gene Expression Regulation / Q000187:drug effects; D006207:Half-Life; D006801:Humans; D007377:Interleukin-3 / Q000235:genetics*; D015847:Interleukin-4 / Q000235:genetics*; D007700:Kinetics; D009693:Nucleic Acid Hybridization; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D013601:T-Lymphocytes / Q000378:metabolism*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014158:Transcription, Genetic
D007377:Interleukin-3; D012333:RNA, Messenger; D003208:Concanavalin A; D015847:Interleukin-4; D016572:Cyclosporine; D003513:Cycloheximide; D013755:Tetradecanoylphorbol Acetate