The response of gamma interferon activation factor is under developmental control in cells of the macrophage lineage.
Gamma interferon activation factor (GAF) rapidly induces transcriptional activation of gamma interferon (IFN-gamma)-responsive genes. Conversion of the GAF from a latent cytoplasmic to an activated, DNA-binding form is an immediate step in the cellular response to IFN-gamma. The amount of IFN-gamma-activated GAF, measured by exonuclease III protection or gel shift assays, increased strongly upon monocytic differentiation of U937 cells. Activated GAF contained the IFN-responsive 91-kDa protein as its DNA-binding activity in gel shift or exonuclease III assays could be inhibited through direct addition of specific antiserum, and it was not present in p91-immunodepleted extracts. There was a differentiation-induced increase in the amount of nonphosphorylated (latent) p91. Transcription rate measurement demonstrated a strong induction of the p91 gene during monocytic differentiation of U937 cells. The amount of p91 which was rapidly phosphorylated in response to IFN-gamma was found to be much higher in the differentiated cells and suggested a differentiation-controlled increase in the signaling leading to p91 phosphorylation. Concomitantly with a better GAF response, transcriptional activation of IFN-gamma-induced genes and the expression of GAF-dependent, transfected reporter plasmids increased in differentiated U937 monocytes. The promonocyte-monocyte transition also affected the IFN-alpha-responsive transcription factor ISGF-3. Differentiated U937 cells contained more of both the alpha-component p91 and the gamma-component p48, which constitutes the DNA-binding subunit of the complex. Our study thus provides evidence that the synthesis of specific transcription factors can be a regulated event to control the cytokine responsiveness of cells during development.
Fraunhofer Institute for Toxicology and Molecular Biology, Hannover, Germany.
A
A
Eilers
D
D
Seegert
C
C
Schindler
M
M
Baccarini
T
T
Decker
D001665:Binding Sites; D002454:Cell Differentiation / Q000187:drug effects; D002467:Cell Nucleus / Q000502:physiology; D015500:Chloramphenicol O-Acetyltransferase / Q000235:genetics / Q000378:metabolism; D003593:Cytoplasm / Q000502:physiology; D005090:Exodeoxyribonucleases / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D050832:Interferon-Stimulated Gene Factor 3; D007371:Interferon-gamma / Q000494:pharmacology*; D046911:Macromolecular Substances; D008264:Macrophages / Q000166:cytology / Q000502:physiology*; D010750:Phosphoproteins / Q000302:isolation & purification / Q000378:metabolism; D010766:Phosphorylation; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014157:Transcription Factors / Q000378:metabolism*; D014158:Transcription, Genetic / Q000187:drug effects; D014162:Transfection; D014407:Tumor Cells, Cultured
D050832:Interferon-Stimulated Gene Factor 3; D046911:Macromolecular Substances; D010750:Phosphoproteins; D014157:Transcription Factors; C079868:gamma interferon activation factor; D007371:Interferon-gamma; D015500:Chloramphenicol O-Acetyltransferase; D005090:Exodeoxyribonucleases; C020133:exodeoxyribonuclease III; D013755:Tetradecanoylphorbol Acetate