title: Hoxb4 transduction down-regulates Geminin protein, providing hematopoietic stem and progenitor cells with proliferation potential.
abstract: Retrovirus-mediated transduction of Hoxb4 enhances hematopoietic stem cell (HSC) activity and enforced expression of Hoxb4 induces in vitro development of HSCs from differentiating mouse embryonic stem cells, but the underlying molecular mechanism remains unclear. We previously showed that the HSC activity was abrogated by accumulated Geminin, an inhibitor for the DNA replication licensing factor Cdt1 in mice deficient in Rae28 (also known as Phc1), which encodes a member of Polycomb-group complex 1. In this study we found that Hoxb4 transduction reduced accumulated Geminin in Rae28-deficient mice, despite increasing the mRNA, and restored the impaired HSC activity. Supertransduction of Geminin suppressed the HSC activity induced by Hoxb4 transduction, whereas knockdown of Geminin promoted the clonogenic and replating activities, indicating the importance of Geminin regulation in the molecular mechanism underlying Hoxb4 transduction-mediated enhancement of the HSC activity. This facilitated our investigation of how transduced Hoxb4 reduced Geminin. We showed in vitro and in vivo that Hoxb4 and the Roc1 (also known as Rbx1)-Ddb1-Cul4a ubiquitin ligase core component formed a complex designated as RDCOXB4, which acted as an E3 ubiquitin ligase for Geminin and down-regulated Geminin through the ubiquitin-proteasome system. Down-regulated Geminin and the resultant E2F activation may provide cells with proliferation potential by increasing a DNA prereplicative complex loaded onto chromatin. Here we suggest that transduced Hoxb4 down-regulates Geminin protein probably by constituting the E3 ubiquitin ligase for Geminin to provide hematopoietic stem and progenitor cells with proliferation potential.
authors.affiliation: Department of Stem Cell Biology, Research Institute for Radiation Biology and Medicine, Hiroshima University, Hiroshima 734-8553, Japan.
authors.forename: Yoshinori
authors.initials: Y
authors.lastname: Ohno
authors.forename: Shin'ichiro
authors.initials: S
authors.lastname: Yasunaga
authors.forename: Motoaki
authors.initials: M
authors.lastname: Ohtsubo
authors.forename: Sayaka
authors.initials: S
authors.lastname: Mori
authors.forename: Miyuki
authors.initials: M
authors.lastname: Tsumura
authors.forename: Satoshi
authors.initials: S
authors.lastname: Okada
authors.forename: Tomohiko
authors.initials: T
authors.lastname: Ohta
authors.forename: Kiyoshi
authors.initials: K
authors.lastname: Ohtani
authors.forename: Masao
authors.initials: M
authors.lastname: Kobayashi
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Takihara
mesh_terms: D000818:Animals; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism*; D002454:Cell Differentiation / Q000502:physiology*; D049109:Cell Proliferation; D044842:Cullin Proteins / Q000235:genetics / Q000378:metabolism; D004261:DNA Replication; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D050684:E2F Transcription Factors / Q000235:genetics / Q000378:metabolism; D064248:Geminin; D057809:HEK293 Cells; D006412:Hematopoietic Stem Cells / Q000166:cytology / Q000502:physiology*; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D064111:Minichromosome Maintenance Complex Component 2; D046912:Multiprotein Complexes / Q000378:metabolism; D034521:Nuclear Matrix-Associated Proteins / Q000235:genetics / Q000378:metabolism; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D029543:Nucleocytoplasmic Transport Proteins / Q000235:genetics / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D014161:Transduction, Genetic
chemical_list: D002352:Carrier Proteins; D018797:Cell Cycle Proteins; C491940:Cul4a protein, mouse; D044842:Cullin Proteins; D004268:DNA-Binding Proteins; C490415:Ddb1 protein, mouse; D050684:E2F Transcription Factors; D064248:Geminin; C577997:Gmnn protein, mouse; D018398:Homeodomain Proteins; C513262:Hoxb4 protein, mouse; D046912:Multiprotein Complexes; D034521:Nuclear Matrix-Associated Proteins; D009687:Nuclear Proteins; D029543:Nucleocytoplasmic Transport Proteins; C540494:RBX1 protein, mouse; C490521:Rae1 protein, mouse; C498645:Ris2 protein, mouse; D014157:Transcription Factors; D064111:Minichromosome Maintenance Complex Component 2