Transcriptional and posttranscriptional regulation of the expression of the erythropoietin receptor gene in human erythropoietin-responsive cell lines.
With erythroid differentiation, committed progenitor cells acquire the ability to respond to erythropoietin (Epo). Epo interacts with target cells through the Epo receptor (Epo-R), whose expression is tightly regulated in a lineage-specific fashion. Epo-R expression is presumed to be progressively activated or repressed as cells progress along the erythroid or the myeloid pathway, respectively. Little is known of the mechanisms that underlie the erythroid-specific expression of the Epo-R gene. GATA-1, the major known transcription factor involved in Epo-R gene regulation, is not erythroid-specific. We have studied the regulation of the expression of the Epo-R gene in two related human Epo-responsive cell lines, UT-7 and UT-7 Epo. These lines express Epo-R at high levels because of amplification of the endogenous gene, which is apparently not rearranged. Treatment for 6 to 24 hours with the tumor promoter, phorbol myristate acetate (PMA), or 24 hours of growth factor starvation (Epo or granulocyte/macrophage colony-stimulating factor [GM-CSF]) decreased or increased the levels of Epo-R mRNA, respectively. In the case of growth factor starvation, the increase (approximately equal to threefold) in the level of Epo-R mRNA correlated directly with an increase in the rate of Epo-R gene transcription as measured by run-off assay. Both increases were observed as early as 3 hours after the growth factor was withdrawn and were reversible; levels of mRNA and transcription rates returned to baseline 3 hours after the cells were reexposed to growth factors. The changes in Epo-R expression after growth factor starvation were coordinated with changes in the level of expression of GATA-1 that were detected both at the mRNA and at the gene transcription level under these conditions (suggesting that GATA-1 was responsible for this upregulation). During PMA treatment, after a transient increase in Epo-R mRNA at 1 hour, a progressive decline in the level of Epo-R mRNA was observed; the level of Epo-R mRNA decreased by 50%, and fell below the level of detection by 6 and 24 hours, respectively. This decrement was explained in part by a fourfold reduction in the rate of gene transcription as well as a reduction (measured as levels of Epo-R mRNA in the presence of actinomycin D) in mRNA stability. The changes in transcription rate occurred in the absence of changes in the level of GATA-1 binding activity.(ABSTRACT TRUNCATED AT 400 WORDS)
Migliaccio
A R
AR
New York Blood Center, NY 10021.
Jiang
Y
Y
Migliaccio
G
G
Nicolis
S
S
Crotta
S
S
Ronchi
A
A
Ottolenghi
S
S
Adamson
J W
JW
D015152:Blotting, Northern; D002455:Cell Division / Q000187:drug effects; D002460:Cell Line; D004268:DNA-Binding Proteins / Q000096:biosynthesis*; D050981:Erythroid-Specific DNA-Binding Factors; D004921:Erythropoietin / Q000494:pharmacology*; D050982:GATA1 Transcription Factor; D005786:Gene Expression Regulation / Q000187:drug effects; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases / Q000096:biosynthesis; D016178:Granulocyte-Macrophage Colony-Stimulating Factor / Q000494:pharmacology; D006801:Humans; D007700:Kinetics; D009857:Oncogenes / Q000187:drug effects; D012323:RNA Processing, Post-Transcriptional; D012333:RNA, Messenger / Q000096:biosynthesis / Q000302:isolation & purification / Q000378:metabolism; D017467:Receptors, Erythropoietin / Q000096:biosynthesis*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D013997:Time Factors; D014157:Transcription Factors / Q000096:biosynthesis*; D014158:Transcription, Genetic; D016335:Zinc Fingers
D004268:DNA-Binding Proteins; D050981:Erythroid-Specific DNA-Binding Factors; D050982:GATA1 Transcription Factor; C494688:GATA1 protein, human; D012333:RNA, Messenger; D017467:Receptors, Erythropoietin; D014157:Transcription Factors; D004921:Erythropoietin; D016178:Granulocyte-Macrophage Colony-Stimulating Factor; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases; D013755:Tetradecanoylphorbol Acetate