title: Hoxa9 transduction induces hematopoietic stem and progenitor cell activity through direct down-regulation of geminin protein.
abstract: Hoxb4, a 3'-located Hox gene, enhances hematopoietic stem cell (HSC) activity, while a subset of 5'-located Hox genes is involved in hematopoiesis and leukemogenesis, and some of them are common translocation partners for Nucleoporin 98 (Nup98) in patients with leukemia. Although these Hox gene derivatives are believed to act as transcription regulators, the molecular involvement of the Hox gene derivatives in hematopoiesis and leukemogenesis remains largely elusive. Since we previously showed that Hoxb4 forms a complex with a Roc1-Ddb1-Cul4a ubiquitin ligase core component and functions as an E3 ubiquitin ligase activator for Geminin, we here examined the E3 ubiquitin ligase activities of the 5'-located Hox genes, Hoxa9 and Hoxc13, and Nup98-Hoxa9. Hoxa9 formed a similar complex with the Roc1-Ddb1-Cul4a component to induce ubiquitination of Geminin, but the others did not. Retroviral transduction-mediated overexpression or siRNA-mediated knock-down of Hoxa9 respectively down-regulated or up-regulated Geminin in hematopoietic cells. And Hoxa9 transduction-induced repopulating and clonogenic activities were suppressed by Geminin supertransduction. These findings suggest that Hoxa9 and Hoxb4 differ from Hoxc13 and Nup98-Hoxa9 in their molecular role in hematopoiesis, and that Hoxa9 induces the activity of HSCs and hematopoietic progenitors at least in part through direct down-regulation of Geminin.
authors: Department of Stem Cell Biology, Research Institute for Radiation Biology and Medicine, Hiroshima University, Hiroshima, Japan.
authors: Yoshinori
authors: Y
authors: Ohno
authors: Shin'ichiro
authors: S
authors: Yasunaga
authors: Salima
authors: S
authors: Janmohamed
authors: Motoaki
authors: M
authors: Ohtsubo
authors: Keita
authors: K
authors: Saeki
authors: Toshiaki
authors: T
authors: Kurogi
authors: Keichiro
authors: K
authors: Mihara
authors: Norman N
authors: NN
authors: Iscove
authors: Yoshihiro
authors: Y
authors: Takihara
mesh_terms: D000818:Animals; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism*; D003114:Colony-Forming Units Assay / Q000379:methods; D044842:Cullin Proteins / Q000235:genetics / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D015536:Down-Regulation; D064248:Geminin; D057809:HEK293 Cells; D006412:Hematopoietic Stem Cells / Q000166:cytology / Q000378:metabolism*; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D015151:Immunoblotting; D051379:Mice; D008810:Mice, Inbred C57BL; D028861:Nuclear Pore Complex Proteins / Q000235:genetics / Q000378:metabolism; D011485:Protein Binding; D034622:RNA Interference; D012190:Retroviridae / Q000235:genetics; D061987:Sf9 Cells; D014161:Transduction, Genetic; D054875:Ubiquitination
chemical_list: C114234:CUL4A protein, human; D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D044842:Cullin Proteins; C091435:DDB1 protein, human; D004268:DNA-Binding Proteins; C577995:GMNN protein, human; D064248:Geminin; C410305:HOXC13 protein, human; D018398:Homeodomain Proteins; D028861:Nuclear Pore Complex Proteins; C479529:RBX1 protein, human; C097899:homeobox protein HOXA9; C093350:nuclear pore complex protein 98