title: E4F1: a novel candidate factor for mediating BMI1 function in primitive hematopoietic cells.
abstract: The Polycomb group gene Bmi1 is essential for the proliferation of neural and hematopoietic stem cells. Much remains to be learned about the pathways involved in the severe hematopoietic phenotype observed in Bmi1 homozygous mutant mice except for the fact that loss of p53 or concomitant loss of p16(Ink4a) and p19(Arf) functions achieves only a partial rescue. Here we report the identification of E4F1, an inhibitor of cellular proliferation, as a novel BMI1-interacting partner in hematopoietic cells. We provide evidence that Bmi1 and E4f1 genetically interact in the hematopoietic compartment to regulate cellular proliferation. Most importantly, we demonstrate that reduction of E4f1 levels through RNA interference mediated knockdown is sufficient to rescue the clonogenic and repopulating ability of Bmi1(-/-) hematopoietic cells up to 3 mo post-transplantation. Using cell lines and MEF, we also demonstrate that INK4A/ARF and p53 are not essential for functional interaction between Bmi1 and E4f1. Together, these findings identify E4F1 as a key modulator of BMI1 activity in primitive hematopoietic cells.
authors.affiliation: Laboratory of Molecular Genetics of Hematopoietic Stem Cells, Institut de Recherche en Immunologie et Cancérologie (IRIC), CP 6128 succursale Centre-Ville, Montréal, Québec, Canada.
authors.forename: Jalila
authors.initials: J
authors.lastname: Chagraoui
authors.forename: Sherry L
authors.initials: SL
authors.lastname: Niessen
authors.forename: Julie
authors.initials: J
authors.lastname: Lessard
authors.forename: Simon
authors.initials: S
authors.lastname: Girard
authors.forename: Philippe
authors.initials: P
authors.lastname: Coulombe
authors.forename: Martin
authors.initials: M
authors.lastname: Sauvageau
authors.forename: Sylvain
authors.initials: S
authors.lastname: Meloche
authors.forename: Guy
authors.initials: G
authors.lastname: Sauvageau
mesh_terms: D000818:Animals; D017209:Apoptosis; D002453:Cell Cycle; D049109:Cell Proliferation; D003114:Colony-Forming Units Assay; D019941:Cyclin-Dependent Kinase Inhibitor p16 / Q000235:genetics / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D006412:Hematopoietic Stem Cells / Q000378:metabolism*; D006801:Humans; D047468:Immunoprecipitation; D008099:Liver / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D009687:Nuclear Proteins / Q000235:genetics / Q000502:physiology*; D063150:Polycomb Repressive Complex 1; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000502:physiology*; D012097:Repressor Proteins / Q000235:genetics / Q000502:physiology*; D012441:Saccharomyces cerevisiae; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D025803:Tumor Suppressor Protein p14ARF / Q000235:genetics / Q000378:metabolism; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism; D020798:Two-Hybrid System Techniques; D044767:Ubiquitin-Protein Ligases
chemical_list: C489421:Bmi1 protein, mouse; D019941:Cyclin-Dependent Kinase Inhibitor p16; D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; D011518:Proto-Oncogene Proteins; D012097:Repressor Proteins; D014157:Transcription Factors; D025803:Tumor Suppressor Protein p14ARF; D016159:Tumor Suppressor Protein p53; C084953:E4f1 protein, mouse; D063150:Polycomb Repressive Complex 1; D044767:Ubiquitin-Protein Ligases