Target proteins of C/EBPalphap30 in AML: C/EBPalphap30 enhances sumoylation of C/EBPalphap42 via up-regulation of Ubc9.
CCAAT/enhancer-binding protein alpha (C/EBPalpha) is a critical regulator for early myeloid differentiation. Mutations in C/EBPalpha occur in 10% of patients with acute myeloid leukemia (AML), leading to the expression of a 30-kDa dominant-negative isoform (C/EBPalphap30). In the present study, using a global proteomics approach to identify the target proteins of C/EBPalphap30, we show that Ubc9, an E2-conjugating enzyme essential for sumoylation, is increased in its expression when C/EBPalphap30 is induced. We confirmed the increased expression of Ubc9 in patients with AML with C/EBPalphap30 mutations compared with other subtypes. We further confirmed that the increase of Ubc9 expression was mediated through increased transcription. Furthermore, we show that Ubc9-mediated enhanced sumoylation of C/EBPalphap42 decreases the transactivation capacity on a minimal C/EBPalpha promoter. Importantly, overexpression of C/EBPalphap30 in granulocyte colony-stimulating factor (G-CSF)-stimulated human CD34(+) cells leads to a differentiation block, which was overcome by the siRNA-mediated silencing of Ubc9. In summary, our data indicate that Ubc9 is an important C/EBPalphap30 target through which C/EBPalphap30 enhances the sumoylation of C/EBPalphap42 to inhibit granulocytic differentiation.
Geletu
Mulu
M
Bone Marrow Transplantation Section, State Center for Cell and Gene Therapy, Department of Internal Medicine IV-Hematology/Oncology, University Hospital of Martin-Luther-University Halle-Wittenberg, Ernst-Grube-Strasse 40, 06120 Halle, Germany.
Balkhi
Mumtaz Y
MY
Peer Zada
Abdul A
AA
Christopeit
Maximilian
M
Pulikkan
John A
JA
Trivedi
Arun K
AK
Tenen
Daniel G
DG
Behre
Gerhard
G
D022762:CCAAT-Enhancer-Binding Proteins / Q000235:genetics / Q000378:metabolism* / Q000502:physiology*; D002454:Cell Differentiation / Q000235:genetics; D015973:Gene Expression Regulation, Leukemic; D020868:Gene Silencing; D005799:Genes, Dominant / Q000502:physiology; D006098:Granulocytes / Q000166:cytology; D006801:Humans; D020014:K562 Cells; D015470:Leukemia, Myeloid, Acute / Q000235:genetics*; D008239:Lysine / Q000378:metabolism; D008954:Models, Biological; D050505:Mutant Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D011499:Protein Processing, Post-Translational / Q000235:genetics*; D011960:Receptors, Estrogen / Q000235:genetics; D025842:SUMO-1 Protein / Q000378:metabolism*; D015533:Transcriptional Activation; D044763:Ubiquitin-Conjugating Enzymes / Q000235:genetics*; D015854:Up-Regulation; D000098843:Ubiquitin-Conjugating Enzyme UBC9
D022762:CCAAT-Enhancer-Binding Proteins; C515848:CEBPA protein, human; D050505:Mutant Proteins; D020033:Protein Isoforms; D011960:Receptors, Estrogen; D025842:SUMO-1 Protein; D044763:Ubiquitin-Conjugating Enzymes; D000098843:Ubiquitin-Conjugating Enzyme UBC9; D008239:Lysine