title: G-CSF induces stabilization of ETS protein Fli-1 during myeloid cell development.
abstract: Granulocyte colony-stimulating factor (G-CSF) is a growth factor that regulates the production and function of neutrophils. G-CSF has been used to treat neutropenia in neonates, pediatric cancer patients, and patients undergoing stem cell transplantation. The regulation of transcription factors mediating G-CSF activity has not been well characterized. The goal of this study was to examine the regulation of the ETS binding protein, Friend leukemia integration site 1 (Fli-1), in myeloid cells treated with G-CSF. Fli-1 has oncogenic properties in humans and mice, and plays a role in vascular and hematopoietic cell development. We previously reported that Fli-1 and the serum response factor bind at adjacent sites within the serum response element-1 of the early growth response gene-1 promoter in the murine myeloid leukemic cell line, NFS60. We also identified that Fli-1 DNA binding increased in G-CSF-treated cells compared with untreated cells. To determine whether the change in binding activity is due to increased Fli-1 transcription or protein stability, we examined endogenous Fli-1 expression in G-CSF-treated or -untreated NFS60 cells. Our results demonstrated that levels of Fli-1 protein, but not RNA, were higher in extracts from cells treated with G-CSF. The increase in Fli-1 protein was also dependent on protein synthesis. Finally, we showed that the half-life of Fli-1 is prolonged in G-CSF-treated cells compared with control-treated cells. These results suggest that G-CSF induces stabilization of Fli-1 protein in myeloid cells, thus proposing a novel mechanism by which hematopoietic growth factors regulate transcription factors.
authors.affiliation: Department of Pediatrics. Division of Hematology-Oncology, Gwynne Hazen Cherry Memorial Laboratories, and Mattel Children's Hospital at UCLA, LA 90095, USA.
authors.forename: Patricia
authors.initials: P
authors.lastname: Mora-Garcia
authors.forename: Jolyn
authors.initials: J
authors.lastname: Wei
authors.forename: Kathleen M
authors.initials: KM
authors.lastname: Sakamoto
mesh_terms: D000818:Animals; D015152:Blotting, Northern; D015153:Blotting, Western; D045744:Cell Line, Tumor; D019070:Cell Lineage; D002467:Cell Nucleus / Q000378:metabolism; D003513:Cycloheximide / Q000494:pharmacology; D004268:DNA-Binding Proteins / Q000378:metabolism / Q000502:physiology*; D016179:Granulocyte Colony-Stimulating Factor / Q000378:metabolism*; D051379:Mice; D022423:Myeloid Cells / Q000166:cytology*; D011485:Protein Binding; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D051789:Proto-Oncogene Protein c-fli-1; D011518:Proto-Oncogene Proteins / Q000378:metabolism / Q000502:physiology*; D012313:RNA / Q000378:metabolism; D013997:Time Factors; D015534:Trans-Activators / Q000378:metabolism / Q000502:physiology*
chemical_list: D004268:DNA-Binding Proteins; C497426:Fli1 protein, mouse; D011500:Protein Synthesis Inhibitors; D051789:Proto-Oncogene Protein c-fli-1; D011518:Proto-Oncogene Proteins; D015534:Trans-Activators; D016179:Granulocyte Colony-Stimulating Factor; D012313:RNA; D003513:Cycloheximide