Regulation of the megakaryocytic glycoprotein IX promoter by the oncogenic Ets transcription factor Fli-1.
Glycoprotein (GP) IX is a subunit of the von Willebrand receptor, GPIb-V-IX, which mediates adhesion of platelets to the subendothelium of damaged blood vessels. Previous characterization of the GPIX promoter identified a functional Ets site that, when disrupted, reduced promoter activity. However, the Ets protein(s) that regulated GPIX promoter expression was unknown. In this study, transient cotransfection of several GPIX promoter/reporter constructs into 293T kidney fibroblasts with a Fli-1 expression vector shows that the oncogenic protein Fli-1 can transactivate the GPIX promoter when an intact GPIX Ets site is present. In addition, Fli-1 binding of the GPIX Ets site was identified in antibody supershift experiments in nuclear extracts derived from hematopoietic human erythroleukemia cells. Comparative studies showed that Fli-1 was also able to transactivate the GPIbalpha and, to a lesser extent, the GPIIb promoter. Immunoblot analysis identified Fli-1 protein in lysates derived from platelets. In addition, expression of Fli-1 was identified immunohistochemically in megakaryocytes derived from CD34(+) cells treated with the megakaryocyte differentiation and proliferation factor, thrombopoietin. These results suggest that Fli-1 is likely to regulate lineage-specific genes during megakaryocytopoiesis.
Bastian
L S
LS
Hematology Section, Medical and Research Services, VA Puget Sound Health Care System, Divisions of Hematology and Oncology, Department of Medicine, University of Washington, Seattle, WA, USA.
Kwiatkowski
B A
BA
Breininger
J
J
Danner
S
S
Roth
G
G
D001665:Binding Sites; D001792:Blood Platelets / Q000378:metabolism*; D002460:Cell Line; D004268:DNA-Binding Proteins / Q000378:metabolism*; D005786:Gene Expression Regulation; D006801:Humans; D020014:K562 Cells; D007668:Kidney; D008156:Luciferases / Q000235:genetics; D008533:Megakaryocytes / Q000378:metabolism*; D019038:Platelet Glycoprotein GPIb-IX Complex / Q000096:biosynthesis / Q000235:genetics*; D011401:Promoter Regions, Genetic; D051789:Proto-Oncogene Protein c-fli-1; D011518:Proto-Oncogene Proteins; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis; D015534:Trans-Activators / Q000378:metabolism*; D015533:Transcriptional Activation; D014162:Transfection
D004268:DNA-Binding Proteins; D019038:Platelet Glycoprotein GPIb-IX Complex; D051789:Proto-Oncogene Protein c-fli-1; D011518:Proto-Oncogene Proteins; D011993:Recombinant Fusion Proteins; D015534:Trans-Activators; D008156:Luciferases