Stem cell factor inhibits erythroid differentiation by modulating the activity of G1-cyclin-dependent kinase complexes: a role for p27 in erythroid differentiation coupled G1 arrest.
Terminal erythroid differentiation is accompanied by decreased expression of c-Kit and decreased proliferation of erythroid progenitor cells. Using a newly established erythroleukemia cell line HB60-5, which proliferates in response to erythropoietin (Epo) and stem cell factor (SCF) and differentiates when stimulated with Epo alone, we characterized several events associated with the cell cycle during erythroid differentiation. Forty-eight h after SCF withdrawal and Epo stimulation, there was strong inhibition of cyclin-dependent kinase (cdk) 4 and cdk6 activities, associated with an increase in the binding of p27 and p15 to cdk6. A significant increase in the binding of p27 to cyclin E- and cyclin A-associated cdk2 correlated with the inhibition of these kinases. In addition, the expression of c-Myc and its downstream transcriptional target Cdc25A were found to be down-regulated during Epo-induced terminal differentiation of HB60-5 cells. The loss of Cdc25A was associated with an increase in the phosphotyrosylation of cyclin E-associated cdk2, which may contribute to cell cycle arrest during differentiation. Although overexpression of p27 in HB60-5 cells caused G1 arrest, it did not promote terminal erythroid differentiation. Thus, the cell cycle arrest that involves p27 is part of a broader molecular program during HB60-5 erythroid differentiation. Moreover, we suggest that SCF stimulation of erythroblasts, in addition to inhibiting erythroid differentiation, activates parallel or sequential signals responsible for maintaining cyclin/cdk activity.
Tamir
A
A
Department of Medical Biophysics, University of Toronto, Cancer Biology Research, Sunnybrook, Ontario, Canada.
Petrocelli
T
T
Stetler
K
K
Chu
W
W
Howard
J
J
Croix
B S
BS
Slingerland
J
J
Ben-David
Y
Y
D000818:Animals; D042846:CDC2-CDC28 Kinases; D018797:Cell Cycle Proteins; D002454:Cell Differentiation / Q000187:drug effects; D019925:Cyclin A / Q000378:metabolism; D056742:Cyclin D2; D056743:Cyclin D3; D019927:Cyclin E / Q000378:metabolism; D056746:Cyclin G; D056766:Cyclin G1; D051357:Cyclin-Dependent Kinase 2; D051358:Cyclin-Dependent Kinase 4; D051361:Cyclin-Dependent Kinase 6; D050760:Cyclin-Dependent Kinase Inhibitor p27; D018844:Cyclin-Dependent Kinases / Q000378:metabolism*; D016213:Cyclins / Q000378:metabolism*; D015536:Down-Regulation / Q000502:physiology; D004912:Erythrocytes / Q000166:cytology* / Q000201:enzymology; D016193:G1 Phase / Q000502:physiology*; D004915:Leukemia, Erythroblastic, Acute; D051379:Mice; D008807:Mice, Inbred BALB C; D008869:Microtubule-Associated Proteins / Q000235:genetics / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D011518:Proto-Oncogene Proteins; D016196:S Phase / Q000502:physiology; D019089:Stem Cell Factor / Q000494:pharmacology*; D014162:Transfection; D014407:Tumor Cells, Cultured; D025521:Tumor Suppressor Proteins; D020687:cdc25 Phosphatases / Q000378:metabolism
C486196:Ccnd2 protein, mouse; C534697:Ccnd3 protein, mouse; C534703:Ccng1 protein, mouse; C493961:Cdkn1b protein, mouse; D018797:Cell Cycle Proteins; D019925:Cyclin A; D056742:Cyclin D2; D056743:Cyclin D3; D019927:Cyclin E; D056746:Cyclin G; D056766:Cyclin G1; D016213:Cyclins; D008869:Microtubule-Associated Proteins; D011518:Proto-Oncogene Proteins; D019089:Stem Cell Factor; D025521:Tumor Suppressor Proteins; D050760:Cyclin-Dependent Kinase Inhibitor p27; D017346:Protein Serine-Threonine Kinases; D042846:CDC2-CDC28 Kinases; C495893:Cdk2 protein, mouse; C495902:Cdk4 protein, mouse; C495912:Cdk6 protein, mouse; D051357:Cyclin-Dependent Kinase 2; D051358:Cyclin-Dependent Kinase 4; D051361:Cyclin-Dependent Kinase 6; D018844:Cyclin-Dependent Kinases; C517005:Cdc25a protein, mouse; D020687:cdc25 Phosphatases