Pbx3 and Meis1 cooperate through multiple mechanisms to support Hox-induced murine leukemia.
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.
Department of Genetics, Friedrich-Alexander-University, Erlangen, Germany.
Maria-Paz
MP
Garcia-Cuellar
Department of Genetics, Friedrich-Alexander-University, Erlangen, Germany.
Julia
J
Steger
Department of Genetics, Friedrich-Alexander-University, Erlangen, Germany.
Elisa
E
Füller
Department of Genetics, Friedrich-Alexander-University, Erlangen, Germany.
Katrin
K
Hetzner
Department of Genetics, Friedrich-Alexander-University, Erlangen, Germany robert.slany@fau.de.
Robert K
RK
Slany
D020816:Amino Acid Motifs; D000818:Animals; D001665:Binding Sites; D004195:Disease Models, Animal; D015973:Gene Expression Regulation, Leukemic; D057809:HEK293 Cells; D018398:Homeodomain Proteins / Q000235:genetics* / Q000378:metabolism; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics / Q000378:metabolism; D007938:Leukemia / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D051379:Mice; D008807:Mice, Inbred BALB C; D008969:Molecular Sequence Data; D000075064:Myeloid Ecotropic Viral Integration Site 1 Protein; D009363:Neoplasm Proteins / Q000235:genetics* / Q000378:metabolism; D028861:Nuclear Pore Complex Proteins / Q000235:genetics / Q000378:metabolism; D015514:Oncogene Proteins, Fusion / Q000235:genetics / Q000378:metabolism; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D011485:Protein Binding; D055503:Protein Multimerization; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D055550:Protein Stability; D059748:Proteolysis; D011518:Proto-Oncogene Proteins / Q000235:genetics* / Q000378:metabolism; D015398:Signal Transduction; D054875:Ubiquitination; D051941:fms-Like Tyrosine Kinase 3 / Q000235:genetics / Q000378:metabolism
D018398:Homeodomain Proteins; D047908:Intracellular Signaling Peptides and Proteins; C000616391:MEIS1 protein, human; C000616392:Meis1 protein, mouse; D000075064:Myeloid Ecotropic Viral Integration Site 1 Protein; C400441:NUP98-HOXA9 fusion protein, human; D009363:Neoplasm Proteins; D028861:Nuclear Pore Complex Proteins; D015514:Oncogene Proteins, Fusion; D011518:Proto-Oncogene Proteins; C097899:homeobox protein HOXA9; C515847:tribbles 2 protein, mouse; C090466:proto-oncogene protein Pbx3; C497971:Flt3 protein, mouse; D051941:fms-Like Tyrosine Kinase 3; D017346:Protein Serine-Threonine Kinases; D046988:Proteasome Endopeptidase Complex