Phosphatidylinositol 3-kinase/Akt induced by erythropoietin renders the erythroid differentiation factor GATA-1 competent for TIMP-1 gene transactivation.
The contribution of erythropoietin to the differentiation of the red blood cell lineage remains elusive, and the demonstration of a molecular link between erythropoietin and the transcription of genes associated with erythroid differentiation is lacking. In erythroid cells, expression of the tissue inhibitor of matrix metalloproteinase (TIMP-1) is strictly dependent on erythropoietin. We report here that erythropoietin regulates the transcription of the TIMP-1 gene upon binding to its receptor in erythroid cells by triggering the activation of phosphatidylinositol 3-kinase (PI3K)/Akt. We found that Akt directly phosphorylates the transcription factor GATA-1 at serine 310 and that this site-specific phosphorylation is required for the transcriptional activation of the TIMP-1 promoter. This chain of events can be recapitulated in nonerythroid cells by transfection of the implicated molecular partners, resulting in the expression of the normally silent endogenous TIMP-1 gene. Conversely, TIMP-1 secretion is profoundly decreased in erythroid cells from fetal livers of transgenic knock-in mice homozygous for a GATA(S310A) gene, which encodes a GATA-1 mutant that cannot be phosphorylated at Ser(310). Furthermore, retrovirus-mediated expression of GATA(S310A) into GATA-1(null)-derived embryonic stem cells decreases the rate of hemoglobinization by more than 50% compared to expressed wild-type GATA-1. These findings provide the first example of a chain of coupling mechanisms between the binding of erythropoietin to its receptor and GATA-1-dependent gene expression.
Pubmed ID: 16107690 RIS Download
Amino Acid Sequence | Animals | Base Sequence | Binding Sites | Cell Differentiation | Cells, Cultured | Cercopithecus aethiops | DNA-Binding Proteins | Erythroid Cells | Erythroid-Specific DNA-Binding Factors | Erythropoietin | GATA1 Transcription Factor | Humans | Mice | Mice, Transgenic | Molecular Sequence Data | Phosphatidylinositol 3-Kinases | Phosphoserine | Protein-Serine-Threonine Kinases | Proto-Oncogene Proteins | Proto-Oncogene Proteins c-akt | Receptors, Erythropoietin | Signal Transduction | Tissue Inhibitor of Metalloproteinase-1 | Transcription Factors | Transcription, Genetic | Transcriptional Activation