title: Thrombopoietin regulates IEX-1 gene expression through ERK-induced AML1 phosphorylation.
abstract: The extracellular signal-regulated kinases (ERKs) are required for thrombopoietin (TPO) functions on hematopoietic cells, but the ERKs targets involved remain unknown. Here we show that the regulation of the immediate early gene X-1 (IEX-1), identified as an ERK substrate in response to TPO, was mediated by an ERK-dependent phosphorylation of AML1. The addition of TPO to UT7-Mpl cells and primary megakaryocytes induced gene expression of IEX-1. Neither erythropoietin (EPO) nor granulocyte macrophage-colony stimulating factor (GM-CSF) was able to activate IEX-1 gene expression in UT7-Mpl cells. The induced expression was mediated by a transcriptional activation of the IEX-1 promoter and required an AML1-binding site located at -1068. The direct involvement of AML1 in the regulation of IEX-1 gene expression was shown by both the use of AML1 mutants and by shRNA experiments targeting endogenous AML1. Finally, the ability of TPO to induce the IEX-1 gene expression was inhibited by U0126, a specific inhibitor of the ERKs activator MEK and AML1 transcriptional activity was shown to be modulated by TPO through ERK-dependent phosphorylation. Taken together, these data suggest that AML1 plays a role in modulating the IEX-1 expression and that the ERK-dependent AML1 phosphorylation regulates the TPO-mediated activation of IEX-1.
authors.affiliation: Institut Cochin, Département Hématologie, Paris, France.
authors.forename: Virginie
authors.initials: V
authors.lastname: Hamelin
authors.forename: Claire
authors.initials: C
authors.lastname: Letourneux
authors.forename: Paul-Henri
authors.initials: PH
authors.lastname: Romeo
authors.forename: Françoise
authors.initials: F
authors.lastname: Porteu
authors.forename: Murielle
authors.initials: M
authors.lastname: Gaudry
mesh_terms: D051017:Apoptosis Regulatory Proteins; D002070:Butadienes / Q000494:pharmacology; D045744:Cell Line, Tumor; D050676:Core Binding Factor Alpha 2 Subunit / Q000235:genetics / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D005786:Gene Expression Regulation / Q000187:drug effects* / Q000502:physiology; D006801:Humans; D017874:Immediate-Early Proteins / Q000096:biosynthesis*; D020930:MAP Kinase Kinase Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D008533:Megakaryocytes / Q000166:cytology / Q000378:metabolism*; D008565:Membrane Proteins; D009154:Mutation; D009363:Neoplasm Proteins / Q000096:biosynthesis*; D009570:Nitriles / Q000494:pharmacology; D010766:Phosphorylation / Q000187:drug effects; D011499:Protein Processing, Post-Translational / Q000187:drug effects* / Q000502:physiology; D050436:Regulatory Elements, Transcriptional / Q000502:physiology; D013926:Thrombopoietin / Q000378:metabolism / Q000494:pharmacology*; D014158:Transcription, Genetic / Q000187:drug effects / Q000276:immunology
chemical_list: D051017:Apoptosis Regulatory Proteins; D002070:Butadienes; D050676:Core Binding Factor Alpha 2 Subunit; D004791:Enzyme Inhibitors; C099815:IER3 protein, human; D017874:Immediate-Early Proteins; D008565:Membrane Proteins; D009363:Neoplasm Proteins; D009570:Nitriles; C493728:RUNX1 protein, human; C113580:U 0126; D013926:Thrombopoietin; D048049:Extracellular Signal-Regulated MAP Kinases; D020930:MAP Kinase Kinase Kinases