title: Molecular interactions involved in HOXB4-induced activation of HSC self-renewal.
abstract: HOXB4 overexpression induces unique in vivo and in vitro expansion of hemopoietic stem cells (HSCs) without causing leukemia. Very little is known about the molecular basis underlying HOXB4-induced HSC self-renewal. We now report the in vitro proliferation and in vivo expansion capacity of primary bone marrow (BM) cells engineered to overexpress selected HOXB4 point mutants lacking either the capacity to directly bind DNA (HOXB4(A)), or to cooperate with members of the PBX family (HOXB4(W-->G)) in DNA binding. The DNA binding-incompetent HOXB4 mutant failed to enhance the proliferation activity of transduced BM populations in vitro and HSC expansion in vivo. In contrast, the HOXB4(W-->G) mutant conferred a pronounced in vitro proliferation advantage to the transduced BM populations, and dramatically enhanced their in vivo regenerative potential. We also demonstrate a correlation between HOXB4 protein levels and in vitro proliferative capacity of primary BM cells. Our observations thus suggest that the capacity of HOXB4 to induce HSC expansions is DNA-binding dependent and does not require direct HOX/PBX interaction, and sets the stage for identifying HOXB4-dependent targets involved in HSC expansion.
authors.affiliation: The Institut de Recherche en Immunovirologie et en Cancérlogie, Pavillon Roger-Gaudry, Université de Montréal, C.P.6128, Succursale Centre-ville, Montréal, QC, Canada.
authors.forename: Nathalie
authors.initials: N
authors.lastname: Beslu
authors.forename: Jana
authors.initials: J
authors.lastname: Krosl
authors.forename: Mélanie
authors.initials: M
authors.lastname: Laurin
authors.forename: Nadine
authors.initials: N
authors.lastname: Mayotte
authors.forename: Keith R
authors.initials: KR
authors.lastname: Humphries
authors.forename: Guy
authors.initials: G
authors.lastname: Sauvageau
mesh_terms: D000818:Animals; D002455:Cell Division; D002460:Cell Line; D004247:DNA / Q000378:metabolism; D015870:Gene Expression; D006412:Hematopoietic Stem Cells / Q000166:cytology* / Q000378:metabolism*; D018398:Homeodomain Proteins / Q000235:genetics* / Q000378:metabolism*; D006801:Humans; D051379:Mice; D009154:Mutation / Q000235:genetics; D011485:Protein Binding; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism*; D014364:Tryptophan / Q000235:genetics / Q000378:metabolism
chemical_list: C090460:HOXB4 protein, human; D018398:Homeodomain Proteins; C513262:Hoxb4 protein, mouse; D014157:Transcription Factors; D014364:Tryptophan; D004247:DNA