Subtle distinct regulations of late erythroid molecular events by PI3K/AKT-mediated activation of Spi-1/PU.1 oncogene autoregulation loop

Autor: Alexandre Douablin, Faouzi Baklouti, Osman Breig, Orianne Théoleyre
Rok vydání: 2010
Předmět:
Cancer Research
Time Factors
animal structures
RNA Splicing
animal diseases
Cellular differentiation
Biology
Mice
Phosphatidylinositol 3-Kinases
Exon
Erythroid Cells
Downregulation and upregulation
Cell Line
Tumor
Proto-Oncogene Proteins
Serine
Genetics
Animals
Homeostasis
Dimethyl Sulfoxide
Phosphorylation
Erythropoietin
Protein Kinase Inhibitors
Molecular Biology
Protein kinase B
PI3K/AKT/mTOR pathway
Phosphoinositide-3 Kinase Inhibitors
Regulation of gene expression
Microfilament Proteins
Cell Differentiation
Blood Proteins
Exons
Oncogenes
biochemical phenomena
metabolism
and nutrition
bacterial infections and mycoses
Molecular biology
Globins
Up-Regulation
Gene Expression Regulation
Neoplastic
Organ Specificity
RNA splicing
Trans-Activators
bacteria
Proto-Oncogene Proteins c-akt
Chromatin immunoprecipitation
Signal Transduction
Zdroj: Oncogene. 29:2807-2816
ISSN: 1476-5594
0950-9232
Popis: Spi-1/PU.1 oncogene is downregulated as proerythroblasts undergo terminal differentiation. Insertion of the Friend virus upstream of the Spi-1/PU.1 locus leads to the constitutive upregulation of Spi-1/PU.1, and a subsequent block in the differentiation of the affected erythroblasts. We have shown that sustained overexpression of Spi-1/PU.1 also inhibits the erythroid splicing of protein 4.1R exon 16, irrespective of chemical induction of differentiation. Here, we show a positive feedback loop that couples constitutive phosphatidylinositol 3-kinase (PI3K)/protein kinase B (AKT) signaling to high expression of Spi-1/PU.1 in Friend erythroleukemia cells. Inhibition of PI3K/AKT results in Spi-1/PU.1 downregulation in a stepwise manner and induces cell differentiation. Chromatin immunoprecipitation assays further supported the positive autoregulatory effect of Spi-1/PU.1. Mutational analysis indicated that Ser41, but not Ser148, is necessary for Spi-1/PU.1-mediated repression of hemoglobin expression, whereas both Ser residues are required for Spi-1/PU.1 inhibition of the erythroid splicing event. We further show that inhibition of the erythroid transcriptional and splicing events are strictly dependent on distinct Spi-1/PU.1 phosphorylation modifications rather than Spi-1/PU.1 expression level per se. Our data further support the fact that Spi-1/PU.1 inhibits 4.1R erythroid splicing through two different pathways, and bring new insights into the extracellular signal impact triggered by erythropoietin on late erythroid regulatory program, including pre-mRNA splicing.
Databáze: OpenAIRE
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