title: The E3 ubiquitin-protein ligase Triad1 inhibits clonogenic growth of primary myeloid progenitor cells.
abstract: Protein ubiquitination plays important roles in a variety of basic cellular processes. Proteins are ubiquitinated by E2-E3 ubiquitin ligase complexes. Depending on the type of ubiquitin chain conjugated, proteins are either targeted for degradation by the proteasome or their activity is specifically altered. We describe a novel conserved nuclear protein, Triad1 (2 RING [really interesting new gene] fingers and DRIL [double RING finger linked] 1), which is strongly induced during myeloid differentiation. Triad1 contains a TRIAD motif that harbors 2 RING finger structures. Triad1 binds the E2 ubiquitin-conjugating enzyme UbcH7 as well as ubiquitinated proteins and supports the formation of ubiquitin chains that are recognized by the proteasome. The biologic function of Triad1 in myelopoiesis was studied by performing granulocyte-macrophage colony-forming unit (CFU-GM) assays using retrovirally transduced primary murine bone marrow cells. Triad1 severely inhibited myeloid colony formation. In contrast, 2 Triad1 RING finger point mutants that failed to bind UbcH7 did not affect colony formation. Moreover, proteasome inhibition counteracted the inhibition of colony formation exerted by wild-type Triad1. In liquid cultures, Triad1 did not influence differentiation but strongly inhibited proliferation resulting in a G0/G1 accumulation. We conclude that proteasomal degradation of proteins that are ubiquitinated by Triad1 affects the clonogenic growth of primary myeloid progenitor cells.
authors.affiliation: Central Hematology Laboratory, University Medical Center Nijmegen, PO BOX 9101, 6500 HB Nijmegen, The Netherlands.
authors.forename: Jurgen A F
authors.initials: JA
authors.lastname: Marteijn
authors.forename: Liesbeth
authors.initials: L
authors.lastname: van Emst
authors.forename: Claudia A J
authors.initials: CA
authors.lastname: Erpelinck-Verschueren
authors.forename: Gorica
authors.initials: G
authors.lastname: Nikoloski
authors.forename: Aswin
authors.initials: A
authors.lastname: Menke
authors.forename: Theo
authors.initials: T
authors.lastname: de Witte
authors.forename: Bob
authors.initials: B
authors.lastname: Löwenberg
authors.forename: Joop H
authors.initials: JH
authors.lastname: Jansen
authors.forename: Bert A
authors.initials: BA
authors.lastname: van der Reijden
mesh_terms: D000818:Animals; D002454:Cell Differentiation; D002467:Cell Nucleus / Q000235:genetics / Q000378:metabolism; D049109:Cell Proliferation; D002478:Cells, Cultured; D006098:Granulocytes / Q000166:cytology / Q000378:metabolism; D006801:Humans; D051379:Mice; D023461:Myeloid Progenitor Cells / Q000166:cytology* / Q000378:metabolism*; D046988:Proteasome Endopeptidase Complex / Q000235:genetics / Q000378:metabolism; D011485:Protein Binding; D014407:Tumor Cells, Cultured; D025801:Ubiquitin / Q000378:metabolism; D044767:Ubiquitin-Protein Ligases / Q000235:genetics / Q000378:metabolism*
chemical_list: D025801:Ubiquitin; C506696:ARIH2 protein, human; C506697:Arih2 protein, mouse; D044767:Ubiquitin-Protein Ligases; D046988:Proteasome Endopeptidase Complex