title: Improved ex vivo expansion of adult hematopoietic stem cells by overcoming CUL4-mediated degradation of HOXB4.
abstract: Direct transduction of the homeobox (HOX) protein HOXB4 promotes the proliferation of hematopoietic stem cells (HSCs) without induction of leukemogenesis, but requires frequent administration to overcome its short protein half-life (∼1 hour). We demonstrate here that HOXB4 protein levels are post-translationally regulated by the CUL4 ubiquitin ligase, and define the degradation signal sequence (degron) of HOXB4 required for CUL4-mediated destruction. Additional HOX paralogs share the conserved degron in the homeodomain and are also subject to CUL4-mediated degradation, indicating that CUL4 likely controls the stability of all HOX proteins. Moreover, we engineered a degradation-resistant HOXB4 that conferred a growth advantage over wild-type HOXB4 in myeloid progenitor cells. Direct transduction of recombinant degradation-resistant HOXB4 protein to human adult HSCs significantly enhanced their maintenance in a more primitive state both in vitro and in transplanted NOD/SCID/IL2R-γ(null) mice compared with transduction with wild-type HOXB4 protein. Our studies demonstrate the feasibility of engineering a stable HOXB4 variant to overcome a major technical hurdle in the ex vivo expansion of adult HSCs and early progenitors for human therapeutic use.
authors.affiliation: Department of Pathology and Laboratory Medicine, Weill Cornell Medical College, New York, NY, USA.
authors.forename: Jennifer
authors.initials: J
authors.lastname: Lee
authors.forename: Jae-Hung
authors.initials: JH
authors.lastname: Shieh
authors.forename: Jianxuan
authors.initials: J
authors.lastname: Zhang
authors.forename: Liren
authors.initials: L
authors.lastname: Liu
authors.forename: Yue
authors.initials: Y
authors.lastname: Zhang
authors.forename: Jae Yong
authors.initials: JY
authors.lastname: Eom
authors.forename: Giovanni
authors.initials: G
authors.lastname: Morrone
authors.forename: Malcolm A S
authors.initials: MA
authors.lastname: Moore
authors.forename: Pengbo
authors.initials: P
authors.lastname: Zhou
mesh_terms: D000328:Adult; D053687:Adult Stem Cells / Q000378:metabolism / Q000502:physiology*; D000818:Animals; D018929:Cell Culture Techniques / Q000379:methods; D049109:Cell Proliferation; D002478:Cells, Cultured; D044842:Cullin Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D005240:Feasibility Studies; D006367:HeLa Cells; D006412:Hematopoietic Stem Cells / Q000378:metabolism / Q000502:physiology*; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D006801:Humans; D051379:Mice; D016688:Mice, Inbred NOD; D016513:Mice, SCID; D008822:Mice, Transgenic; D061251:Primary Cell Culture / Q000379:methods; D015202:Protein Engineering; D059748:Proteolysis; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism* / Q000502:physiology
chemical_list: C114234:CUL4A protein, human; D044842:Cullin Proteins; C090460:HOXB4 protein, human; D018398:Homeodomain Proteins; D014157:Transcription Factors