Differential transcriptional and posttranscriptional regulation of gene expression of the colony-stimulating factors by interleukin-1 and fetal bovine serum in murine fibroblasts.
Colony-stimulating factors (CSF) are important factors in the proliferation and differentiation of hematopoietic progenitor cells (HPC), and in the survival and activation of mature blood cells. Interleukin-1 (IL-1) combined with fetal bovine serum (FBS) strongly induces the expression of macrophage-CSF (M-CSF), granulocyte-CSF (G-CSF), and granulocyte-macrophage-CSF (GM-CSF) in fibroblasts. Here, we report on the regulation of CSF gene expression in murine fibroblasts following IL-1 and FBS stimulation. We demonstrate that 10T1/2 murine fibroblasts induced by FBS or IL-1 accumulate M-CSF messenger RNA (mRNA). G-CSF mRNA expression was induced by IL-1, and not by FBS. For GM-CSF expression, induction with both FBS and IL-1 was required. Blocking studies with actinomycin-D showed that active transcription is essential for accumulation of all three CSF mRNAs. After blocking protein synthesis with cycloheximide, IL-1- or FBS-induced M-CSF expression and IL-1 plus FBS-induced GM-CSF expression still occurred and was increased. IL-1-induced G-CSF expression was completely prevented in these cells by pretreatment with cycloheximide, illustrating that, for this effect, intermediate protein synthesis was required. The half-lives of M-CSF transcripts were not substantially altered by addition of IL-1, FBS, or FBS plus IL-1. Using nuclear run-on assays, we demonstrated that the transcription rate of M-CSF was increased up to 20-fold by the addition of FBS, IL-1, or FBS plus IL-1. After blocking protein synthesis with cycloheximide, IL-1-or FBS-induced increase in M-CSF transcription rate was also observed. GM-CSF transcription increased up to fourfold after induction with FBS or IL-1. G-CSF transcription rate was not altered by FBS or IL-1. Our results indicate that M-CSF expression induced by FBS or IL-1 in these fibroblasts is primarily regulated at the transcriptional level. GM-CSF expression appears to be regulated both transcriptionally and posttranscriptionally, and G-CSF expression is regulated mainly at the posttranscriptional level.
Falkenburg
J H
JH
Department of Medicine (Hematology/Oncology), Indiana University School of Medicine, Indianapolis.
Harrington
M A
MA
de Paus
R A
RA
Walsh
W K
WK
Daub
R
R
Landegent
J E
JE
Broxmeyer
H E
HE
D000818:Animals; D001769:Blood; D002417:Cattle; D002460:Cell Line; D002467:Cell Nucleus / Q000502:physiology; D003115:Colony-Stimulating Factors / Q000235:genetics*; D003470:Culture Media; D003513:Cycloheximide / Q000494:pharmacology; D003609:Dactinomycin / Q000494:pharmacology; D005333:Fetus; D005347:Fibroblasts / Q000187:drug effects / Q000502:physiology; D005786:Gene Expression Regulation / Q000187:drug effects*; D016179:Granulocyte Colony-Stimulating Factor / Q000235:genetics; D016178:Granulocyte-Macrophage Colony-Stimulating Factor / Q000235:genetics; D007375:Interleukin-1 / Q000494:pharmacology*; D007700:Kinetics; D016173:Macrophage Colony-Stimulating Factor / Q000235:genetics; D051379:Mice; D014176:Protein Biosynthesis / Q000187:drug effects*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D014158:Transcription, Genetic / Q000187:drug effects*
D003115:Colony-Stimulating Factors; D003470:Culture Media; D007375:Interleukin-1; D012333:RNA, Messenger; D016179:Granulocyte Colony-Stimulating Factor; D003609:Dactinomycin; D016173:Macrophage Colony-Stimulating Factor; D016178:Granulocyte-Macrophage Colony-Stimulating Factor; D003513:Cycloheximide