A Novel Function of Stat1α and Stat3 Proteins in Erythropoietin-Induced Erythroid Differentiation of a Human Leukemia Cell Line

Blood ◽  
1998 ◽  
Vol 92 (2) ◽  
pp. 462-471 ◽  
Author(s):  
Keita Kirito ◽  
Mie Uchida ◽  
Masaaki Takatoku ◽  
Koichi Nakajima ◽  
Toshio Hirano ◽  
...  

We recently determined that erythropoietin (EPO) activates 3 members of the signal transducer and activator of transcription (STAT) family, Stat1α, Stat3, and Stat5, in the human EPO-dependent cell lines, UT-7 and UT-7/EPO (Kirito et al, J Biol Chem 272:16507, 1997). In addition, we have shown that Stat1α, but not Stat3, is involved in EPO-induced cellular proliferation. In this study, we examined the roles of Stat1α and Stat3 in EPO-induced erythroid differentiation. UT-7/GM was used as a model system, because this cell line can differentiate into erythroid-lineage cells with EPO treatment (Komatsu et al, Blood 89:4021, 1997). We found that EPO did not activate Stat1α or Stat3 in UT-7/GM cells. Transfection experiments showed that both Stat1α and Stat3 inhibited the induction by EPO of γ-globin and erythroid-specific 5-aminolevulinate synthetase transcripts, resulting in a reduction of the percentage of hemoglobin-positive cells. Dominant negative forms of Stat1α or Stat3 promoted the EPO-induced erythroid differentiation of UT-7/GM cells, even in the presence of granulocyte-macrophage colony-stimulating factor, although this cytokine never induced erythroid differentiation of the parent UT-7/GM cells with or without EPO. A cell cycle analysis showed that the constitutive activation of Stat1α, but not Stat3, shortened the period of G0/G1 prolongation caused by EPO stimulation. Taken together, our data suggest that Stat1α and Stat3 act as negative regulators in EPO-induced erythroid differentiation. Specifically, Stat1α may activate a cell cycle-associated gene(s), leading to the entry of cells into the cell cycle.

Blood ◽  
1998 ◽  
Vol 92 (2) ◽  
pp. 462-471 ◽  
Author(s):  
Keita Kirito ◽  
Mie Uchida ◽  
Masaaki Takatoku ◽  
Koichi Nakajima ◽  
Toshio Hirano ◽  
...  

Abstract We recently determined that erythropoietin (EPO) activates 3 members of the signal transducer and activator of transcription (STAT) family, Stat1α, Stat3, and Stat5, in the human EPO-dependent cell lines, UT-7 and UT-7/EPO (Kirito et al, J Biol Chem 272:16507, 1997). In addition, we have shown that Stat1α, but not Stat3, is involved in EPO-induced cellular proliferation. In this study, we examined the roles of Stat1α and Stat3 in EPO-induced erythroid differentiation. UT-7/GM was used as a model system, because this cell line can differentiate into erythroid-lineage cells with EPO treatment (Komatsu et al, Blood 89:4021, 1997). We found that EPO did not activate Stat1α or Stat3 in UT-7/GM cells. Transfection experiments showed that both Stat1α and Stat3 inhibited the induction by EPO of γ-globin and erythroid-specific 5-aminolevulinate synthetase transcripts, resulting in a reduction of the percentage of hemoglobin-positive cells. Dominant negative forms of Stat1α or Stat3 promoted the EPO-induced erythroid differentiation of UT-7/GM cells, even in the presence of granulocyte-macrophage colony-stimulating factor, although this cytokine never induced erythroid differentiation of the parent UT-7/GM cells with or without EPO. A cell cycle analysis showed that the constitutive activation of Stat1α, but not Stat3, shortened the period of G0/G1 prolongation caused by EPO stimulation. Taken together, our data suggest that Stat1α and Stat3 act as negative regulators in EPO-induced erythroid differentiation. Specifically, Stat1α may activate a cell cycle-associated gene(s), leading to the entry of cells into the cell cycle.


Blood ◽  
2006 ◽  
Vol 108 (11) ◽  
pp. 4203-4203
Author(s):  
Nobuyoshi Kosaka ◽  
Yusuke Yamamoto ◽  
Nami Nogawa ◽  
Keiichi Sugiura ◽  
Hiroshi Miyazaki ◽  
...  

Abstract Mature microRNA (miRNA) originated from primary miRNA (pri-miRNA) is a new group of potential regulator for cell differentiation, apoptosis, proliferation and oncogenesis. Some miRNAs were recently identified in hematopoietic cells, while the roles of miRNAs in erythrocytic and megakaryocytic cells had not been well examined. As a first step to explore for miRNAs specific for hematopoietic lineage, the expressions of several known primary microRNAs in erythrocytic and megakaryocytic cell lines, such as TF-1, HL-60, HEK293 and UT-7 leukemia cells, were examined by RT-PCR. We consequently focused on the pri-miR-10a, a primary transcript of miR-10a located within Hox gene clusters, and found the significant expression in TF-1 cells and UT-7/EPO cells. The UT-7/EPO cells were a subline established from the original UT-7 cells, as well as UT-7/GM and UT-7/TPO cells; therefore it was suitable for the further comparative analysis. Interestingly, in UT-7/EPO cells, the expression of pri-miR-10a increased under stimulation of erythropoietin (EPO; 1U/mL and 10U/mL). Based on these observations, it was postulated that pri-miR-10a might involve in modulating erythrocyte differentiation or proliferation. To clarify the role of pri-miR-10a in UT-7/EPO, we have established clonal cell lines by transfecting UT-7/EPO cells with either the control vector or the pri-miR-10a expression vector pCMV-pri-miR10a. Overexpression of pri-miR-10a in the UT-7/EPO cell line (miR10a-UT-7/EPO) was confirmed by RT-PCR. MiR10a-UT-7/EPO showed higher proliferation rate even at low concentration of EPO (0.1 mU/mL). Overexpression of pri-miR-10a did not appear to affect HOXB4 and HOXA1 expression, as similar mRNA levels were seen in both cell lines. It was notable that the cellular size of miR10a-UT-7/EPO became larger than its parental cells. Morphological studies of miR10a-UT-7/EPO were performed in detail. It is possible that miR-10a was capable to modulate morphological features particularly in cellular size relating to cell cycle regulation. For instance, loss of the E2F family members result in marked macrocytic anemia with megaloblastic features in adult mice (Mol Cell. 2000 Aug;6(2):281–91., Mol Cell Biol. 2003 May;23(10):3607–22., Blood. 2006 Aug 1;108(3):886–95.). Data presented here hypothesized that the roles of miR-10a in erythroid cells are tightly associated with cell cycle.


1988 ◽  
Vol 6 (3) ◽  
pp. 209-220 ◽  
Author(s):  
Hiroyuki Tsuda ◽  
Mamoru Sakaguchi ◽  
Makoto Kawakita ◽  
Shimpei Nakazawa ◽  
Taijiro Mori ◽  
...  

Blood ◽  
1993 ◽  
Vol 82 (2) ◽  
pp. 456-464 ◽  
Author(s):  
N Komatsu ◽  
M Yamamoto ◽  
H Fujita ◽  
A Miwa ◽  
K Hatake ◽  
...  

UT-7 is a human leukemic cell line capable of growing in interleukin-3 (IL-3), granulocyte/macrophage colony-stimulating factor (GM-CSF), or erythropoietin (Epo) (Komatsu et al, Cancer Res 51:341, 1991). To study the effect of Epo on proliferation and differentiation of UT-7, we maintained the UT-7 cell culture for more than 6 months in the presence of Epo. As a result, a subline, UT-7/Epo, was established. The growth of UT-7/Epo could be supported by Epo but not by GM-CSF or IL-3. UT- 7/Epo showed a greater level of heme content and ratio of benzidine- positive staining cells than did UT-7. Butyric acid promoted the synthesis of hemoglobin in UT-7/Epo, but not UT-7. Further, the mRNA concentrations of the c-myb oncogene and GM-CSF receptor beta-subunit were decreased substantially in UT-7/Epo cells. These findings showed that UT-7/Epo cells had progressed further in erythroid development than UT-7 cells, and suggested that long-term culture in Epo had promoted this differentiation. Whereas availability of the Epo receptor (Epo-R) for binding of Epo was reduced in UT-7/Epo cells compared with UT-7 cells, the Epo-R showed a similar affinity for Epo. This observation suggested that change(s) in postreceptor signaling step might be involved in the establishment and maintenance of the UT-7/Epo phenotype.


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