Modulation of mRNA expression of a novel human myeloid-selective CCAAT/enhancer binding protein gene (C/EBPε)
DY Chih, AM Chumakov, DJ Park… - Blood, The Journal …, 1997 - ashpublications.org
DY Chih, AM Chumakov, DJ Park, AG Silla, HP Koeffler
Blood, The Journal of the American Society of Hematology, 1997•ashpublications.orgHuman C/EBPε is a newly cloned gene coding for a CCAAT/enhancer binding protein that
may be involved in the regulation of myeloid differentiation. Our studies showed that levels
of C/EBPε mRNA were markedly increased in NB4 cells (promyelocytic leukemia line),
because they were induced by 9-cis retinoic acid (9-cis RA) to differentiate towards
granulocytes. Accumulation of C/EBPε mRNA occurred as early as 1 hour after exposure of
NB4 cells to 9-cis RA (5× 10− 7 mol/L); and at 48 hours, levels were increased by 5.1-fold …
may be involved in the regulation of myeloid differentiation. Our studies showed that levels
of C/EBPε mRNA were markedly increased in NB4 cells (promyelocytic leukemia line),
because they were induced by 9-cis retinoic acid (9-cis RA) to differentiate towards
granulocytes. Accumulation of C/EBPε mRNA occurred as early as 1 hour after exposure of
NB4 cells to 9-cis RA (5× 10− 7 mol/L); and at 48 hours, levels were increased by 5.1-fold …
Abstract
Human C/EBPε is a newly cloned gene coding for a CCAAT/enhancer binding protein that may be involved in the regulation of myeloid differentiation. Our studies showed that levels of C/EBPε mRNA were markedly increased in NB4 cells (promyelocytic leukemia line), because they were induced by 9-cis retinoic acid (9-cis RA) to differentiate towards granulocytes. Accumulation of C/EBPε mRNA occurred as early as 1 hour after exposure of NB4 cells to 9-cis RA (5 × 10−7 mol/L); and at 48 hours, levels were increased by 5.1-fold. Dose-response studies showed that 10−7 to 10−6 mol/L 9-cis RA (12 hours) resulted in peak levels of C/EBPε mRNA; but even 10−10 mol/L 9-cis RA increased levels of these transcripts. NB4 cells pulse-exposed (30 minutes) to all-trans retinoic acid (ATRA), washed, and cultured (3 days) with either dimethylsulfoxide (DMSO) or hexamethylene bisacetamide (HMBA) had a prominent increase in levels of C/EBPε mRNA and an increase in granulocytic differentiation, but exposure to either DMSO or HMBA alone had no effect on base levels of C/EBPε and did not induce differentiation. Macrophage-differentiation of NB4 reduced levels of C/EBPε mRNA. Nuclear run-off assays and half-life studies showed that accumulation of C/EBPε mRNA by 9-cis RA was due to enhanced transcription. Furthermore, this C/EBPε mRNA accumulation did not require synthesis of new protein factors because 9-cis RA induced C/EBPε mRNA accumulation in the absence of new protein synthesis. ATRA also induced expression of C/EBPε protein in NB4 cells, as shown by Western blotting. In contrast to the increase of C/EBPε in 9-cis RA–mediated granulocytic differentiation, the DMSO-induced differentiation of HL-60 cells down the granulocytic pathway was associated with an initial reduction of C/EBPε mRNA levels. In summary, we have discovered that expression of C/EBPε mRNA is markedly enhanced as the NB4 promyelocytes are induced by retinoids to differentiate towards granulocytes. This induction of C/EBPε mRNA expression is transcriptionally mediated and occurs in the absence of synthesis of additional protein factors. We suspect that the C/EBPε promoter/enhancer contains a retinoic acid-response element that is directly stimulated by retinoids.
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