Phosphorylation of forkhead transcription factors by erythropoietin and stem cell factor prevents acetylation and their interaction with coactivator p300 in erythroid progenitor cells.
The mammalian forkhead transcription factors, FOXO3a (FKHRL1), FOXO1a (FKHR) and FOXO4 (AFX) are negatively regulated by PKB/Akt kinase. In the present study we examined the engagement of forkhead family of transcription factors in erythropoietin (Epo)- and stem cell factor (SCF)-mediated signal transduction. Our data show that all three forkhead family members, FOXO3a, FOXO1a and FOXO4 are phosphorylated in human primary erythroid progenitors. Experiments performed to determine various upstream signaling pathways contributing to phosphorylation of forkhead family members show that only PI-3-kinase pathway is required for inactivation of FOXO3a. Our data also demonstrate that during Epo deprivation FOXO3a interacts with the transcriptional coactivator p300 and such interaction is disrupted by stimulation of cells with Epo. To determine the domains in FOXO3a, mediating its interaction with p300, we performed GST pull-down assays and found that the N-terminus region containing the first 52 amino acids was sufficient for binding p300. Finally, our data demonstrate that FOXO3a and FOXO1a are acetylated during growth factor deprivation and such acetylation is reversed by stimulation with Epo. Thus mammalian forkhead transcription factors are involved in Epo and SCF signaling in primary erythroid progenitors and may play a role in the induction of apoptotic and mitogenic signals.
Mahmud
Dolores L
DL
The University of Illinois Medical Center, Chicago, Illinois, USA.
G-Amlak
Maaza
M
Deb
Dilip K
DK
Platanias
Leonidas C
LC
Uddin
Shahab
S
Wickrema
Amittha
A
D000107:Acetylation / Q000187:drug effects; D018797:Cell Cycle Proteins; D002460:Cell Line; D002478:Cells, Cultured; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000378:metabolism*; D015672:Erythroid Precursor Cells / Q000187:drug effects / Q000378:metabolism*; D004921:Erythropoietin / Q000494:pharmacology; D000071161:Forkhead Box Protein O1; D000071316:Forkhead Box Protein O3; D051858:Forkhead Transcription Factors; D016298:Hematopoietic Cell Growth Factors / Q000494:pharmacology*; D006801:Humans; D007700:Kinetics; D009687:Nuclear Proteins / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects; D017434:Protein Structure, Tertiary; D015398:Signal Transduction; D019089:Stem Cell Factor / Q000494:pharmacology; D015534:Trans-Activators / Q000378:metabolism*; D014157:Transcription Factors / Q000737:chemistry / Q000378:metabolism*
D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; C085126:FOXO1 protein, human; C499517:FOXO3 protein, human; C108803:FOXO4 protein, human; D000071161:Forkhead Box Protein O1; D000071316:Forkhead Box Protein O3; D051858:Forkhead Transcription Factors; D016298:Hematopoietic Cell Growth Factors; D009687:Nuclear Proteins; D019089:Stem Cell Factor; D015534:Trans-Activators; D014157:Transcription Factors; D004921:Erythropoietin