Abstract
Hox homeobox transcription factors drive leukemogenesis efficiently only in the presence of Meis or Pbx proteins. Here we show that Pbx3 and Meis1 need to dimerize to support Hox-induced leukemia and we analyze the molecular details of this cooperation. In the absence of Pbx3, Meis1 was highly unstable. As shown by a deletion analysis Meis1 degradation was contingent on a motif coinciding with the Pbx-binding domain. Either deletion of this sequence or binding to Pbx3 prolonged the half-life of Meis1 by preventing its ubiquitination. Meis1 break-down could also be blocked by inhibition of the ubiquitin proteasome system, indicating tight post-transcriptional control. In addition, Meis1 and Pbx3 cooperated genetically as overexpression of Pbx3 induced endogenous Meis1 transcription. These functional interactions translated into in vivo activity. Blocking Meis1/Pbx3 dimerization abrogated the ability to enhance proliferation and colony-forming cell numbers in primary cells transformed by Hoxa9. Furthermore, expression of Meis1 target genes Flt3 and Trib2 was dependent on Pbx3/Meis1 dimerization. This correlated with the requirement of Meis1 to bind Pbx3 in order to form high affinity DNA/Hoxa9/Meis1/Pbx3 complexes in vitro. Finally, kinetics and severity of disease in transplantation assays indicated that Pbx3/Meis1 dimers are rate-limiting factors for Hoxa9-induced leukemia.
Copyright© Ferrata Storti Foundation.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Amino Acid Motifs
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Animals
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Binding Sites
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Disease Models, Animal
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Gene Expression Regulation, Leukemic*
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HEK293 Cells
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Homeodomain Proteins / genetics*
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Homeodomain Proteins / metabolism
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Humans
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Intracellular Signaling Peptides and Proteins / genetics
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Intracellular Signaling Peptides and Proteins / metabolism
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Leukemia / genetics*
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Leukemia / metabolism
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Leukemia / pathology
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Mice
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Mice, Inbred BALB C
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Molecular Sequence Data
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Myeloid Ecotropic Viral Integration Site 1 Protein
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Neoplasm Proteins / genetics*
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Neoplasm Proteins / metabolism
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Nuclear Pore Complex Proteins / genetics
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Nuclear Pore Complex Proteins / metabolism
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Oncogene Proteins, Fusion / genetics
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Oncogene Proteins, Fusion / metabolism
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Proteasome Endopeptidase Complex / metabolism
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Protein Binding
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Protein Multimerization
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Protein Serine-Threonine Kinases / antagonists & inhibitors
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Protein Serine-Threonine Kinases / genetics
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Protein Serine-Threonine Kinases / metabolism
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Protein Stability
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Proteolysis
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Proto-Oncogene Proteins / genetics*
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Proto-Oncogene Proteins / metabolism
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Signal Transduction
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Ubiquitination
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fms-Like Tyrosine Kinase 3 / genetics
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fms-Like Tyrosine Kinase 3 / metabolism
Substances
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Homeodomain Proteins
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Intracellular Signaling Peptides and Proteins
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MEIS1 protein, human
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Meis1 protein, mouse
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Myeloid Ecotropic Viral Integration Site 1 Protein
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NUP98-HOXA9 fusion protein, human
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Neoplasm Proteins
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Nuclear Pore Complex Proteins
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Oncogene Proteins, Fusion
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Proto-Oncogene Proteins
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homeobox protein HOXA9
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tribbles 2 protein, mouse
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proto-oncogene protein Pbx3
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Flt3 protein, mouse
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fms-Like Tyrosine Kinase 3
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Protein Serine-Threonine Kinases
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Proteasome Endopeptidase Complex