Posttranscriptional regulation of the zinc finger-encoding EGR-1 gene by granulocyte-macrophage colony-stimulating factor in human U-937 monocytic leukemia cells: involvement of a pertussis toxin-sensitive G protein.
The EGR-1 gene is an immediate early response gene encoding a zinc finger DNA-binding protein. The present studies have examined the regulation of EGR-1 gene expression in human U-937 monocytic leukemia cells treated with granulocyte-macrophage colony-stimulating factor (GM-CSF). The results demonstrate that GM-CSF rapidly and transiently increases EGR-1 gene expression in U-937 cells. Similar findings were obtained in GM-CSF-treated human monocytes. We also show that the regulation of EGR-1 expression by GM-CSF is a pertussis toxin-sensitive event. The results of nuclear run-on assays further demonstrate that the EGR-1 gene is constitutively transcribed in untreated U-937 cells and that GM-CSF has little effect on this rate of transcription. Inhibition of protein synthesis with cycloheximide also had no detectable effect on EGR-1 gene transcription but was associated with superinduction of EGR-1 mRNA levels in GM-CSF-treated cells. Moreover, the half-life of GM-CSF-induced EGR-1 transcripts was prolonged from 33 to 70 min following inhibition of protein synthesis. Taken together, the results indicate that GM-CSF activates signaling pathways which regulate EGR-1 gene expression through a pertussis toxin-sensitive G protein and that these events increase EGR-1 mRNA levels by a posttranscriptional mechanism. This GM-CSF-dependent regulation of EGR-1 expression may provide a mechanism for transducing signals to the nucleus that are involved in the control of gene transcription.
Bernstein
S H
SH
Laboratory of Clinical Pharmacology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, Massachusetts 02115.
Kharbanda
S M
SM
Sherman
M L
ML
Sukhatme
V P
VP
Kufe
D W
DW
D002461:Cell Line, Transformed; D015973:Gene Expression Regulation, Leukemic; D016178:Granulocyte-Macrophage Colony-Stimulating Factor / Q000494:pharmacology*; D006801:Humans; D007951:Leukemia, Myeloid; D009000:Monocytes / Q000378:metabolism; D037342:Pertussis Toxin; D012323:RNA Processing, Post-Transcriptional; D014158:Transcription, Genetic; D010566:Virulence Factors, Bordetella / Q000494:pharmacology*; D016335:Zinc Fingers / Q000235:genetics*
D010566:Virulence Factors, Bordetella; D016178:Granulocyte-Macrophage Colony-Stimulating Factor; D037342:Pertussis Toxin