Control of HILDA/LIF gene expression in activated human monocytes.
In the present study we have investigated some of the mechanisms involved in HILDA/LIF gene expression in activated human monocytes and compared them to those of G-CSF gene expression, another monocyte-derived cytokine. In the absence of added stimuli, HILDA/LIF mRNA was barely detectable in monocytes. HILDA/LIF mRNA accumulation was weakly induced by stimuli such as LPS or phorbol ester alone, and in a synergistic manner when they were used in combination with 1,25-dihydroxyvitamin D3. Nuclear run-on transcription analysis in U937 cells did not detect an increase of HILDA/LIF gene transcription upon phorbol ester and 1,25-dihydroxyvitamin D3 stimulation. Posttranscriptional control of HILDLA/LIF mRNA levels by an increase in mRNA half-life was demonstrated in the synergy between phorbol ester and 1,25-dihydroxyvitamin D3 and in the superinduction of HILDA/LIF transcript accumulation when CHX was added to stimulated cells shortly before cell harvesting. HILDA/LIF mRNA expression was largely inhibited when U937 cells were treated with CHX either at the onset or 4 h after the beginning of the stimulation period. When CHX was added 2 h before cell harvesting, a superinduction of mRNA accumulation was obtained. G-CSF mRNA accumulation showed a different pattern of response to the same stimuli, in particular a higher rate of response to LPS. In contrast to HILDA/LIF, an augmentation of G-CSF gene transcription was detected in activated monocytic cells when compared to controls. These studies indicate that HILDA/LIF gene expression by phorbol ester- and 1,25-dihydroxyvitamin D3-treated human monocytes has a relatively specific regulation, as compared to G-CSF gene expression, and that it is largely dependent on posttranscriptional mechanisms probably acting through labile, newly synthesized proteins.
Grolleau
D
D
INSERM U211, Nantes, France.
Soulillou
J P
JP
Anegon
I
I
D002117:Calcitriol / Q000494:pharmacology; D002467:Cell Nucleus / Q000502:physiology; D002478:Cells, Cultured; D003513:Cycloheximide / Q000494:pharmacology; D003609:Dactinomycin / Q000494:pharmacology; D015870:Gene Expression; D005786:Gene Expression Regulation / Q000187:drug effects; D016179:Granulocyte Colony-Stimulating Factor / Q000235:genetics; D006131:Growth Inhibitors; D006801:Humans; D015850:Interleukin-6; D053605:Leukemia Inhibitory Factor; D008222:Lymphokines / Q000235:genetics*; D009000:Monocytes / Q000187:drug effects / Q000502:physiology*; D015240:Phorbol 12,13-Dibutyrate / Q000494:pharmacology; D012333:RNA, Messenger / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D014158:Transcription, Genetic / Q000187:drug effects
D006131:Growth Inhibitors; D015850:Interleukin-6; C507837:LIF protein, human; D053605:Leukemia Inhibitory Factor; D008222:Lymphokines; D012333:RNA, Messenger; D016179:Granulocyte Colony-Stimulating Factor; D003609:Dactinomycin; D015240:Phorbol 12,13-Dibutyrate; D003513:Cycloheximide; D002117:Calcitriol