title: Transformation by Tribbles homolog 2 (Trib2) requires both the Trib2 kinase domain and COP1 binding.
abstract: Tribbles homolog 2 (Trib2) is a pseudokinase that induces acute myelogenous leukemia (AML) in mice and is highly expressed in a subset of human AML. Trib2 has 3 distinct regions, a proline-rich N-terminus, a serine/threonine kinase homology domain, and a C-terminal constitutive photomorphogenesis 1 (COP1)-binding domain. We performed a structure-function analysis of Trib2 using in vitro and in vivo assays. The N-terminus was not required for Trib2-induced AML. Deletion or mutation of the COP1-binding site abrogated the ability of Trib2 to degrade CCAAT/enhancer-binding protein-α (C/EBP-α), block granulocytic differentiation, and to induce AML in vivo. Furthermore, COP1 knockdown inhibited the ability of Trib2 to degrade C/EBP-α, showing that it is important for mediating Trib2 activity. We also show that the Trib2 kinase domain is essential for its function. Trib2 contains variant catalytic loop sequences, compared with conventional kinases, that we show are necessary for Trib2 activity. The kinase domain mutants bind, but cannot efficiently degrade, C/EBP-α. Together, our data demonstrate that Trib2 can bind both COP1 and C/EBP-α, leading to degradation of C/EBP-α. Identification of the functional regions of Trib2 that are essential to its oncogenic role provides the basis for developing inhibitors that will block Trib functions in cancer.
authors.affiliation: Department of Pathology and Laboratory Medicine, Abramson Family Cancer Research Institute, Institute for Medicine and Engineering, University of Pennsylvania, Philadelphia, PA, USA.
authors.forename: Karen
authors.initials: K
authors.lastname: Keeshan
authors.forename: Will
authors.initials: W
authors.lastname: Bailis
authors.forename: Priya H
authors.initials: PH
authors.lastname: Dedhia
authors.forename: Maria E
authors.initials: ME
authors.lastname: Vega
authors.forename: Olga
authors.initials: O
authors.lastname: Shestova
authors.forename: Lanwei
authors.initials: L
authors.lastname: Xu
authors.forename: Kristin
authors.initials: K
authors.lastname: Toscano
authors.forename: Sacha N
authors.initials: SN
authors.lastname: Uljon
authors.forename: Stephen C
authors.initials: SC
authors.lastname: Blacklow
authors.forename: Warren S
authors.initials: WS
authors.lastname: Pear
mesh_terms: D000818:Animals; D015153:Blotting, Western; D022763:CCAAT-Enhancer-Binding Protein-alpha / Q000378:metabolism*; D002469:Cell Separation; D002471:Cell Transformation, Neoplastic / Q000737:chemistry* / Q000378:metabolism; D005434:Flow Cytometry; D006801:Humans; D047468:Immunoprecipitation; D047908:Intracellular Signaling Peptides and Proteins / Q000737:chemistry* / Q000378:metabolism*; D051379:Mice; D009687:Nuclear Proteins / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000737:chemistry* / Q000378:metabolism* / Q000037:antagonists & inhibitors; D017434:Protein Structure, Tertiary; D013329:Structure-Activity Relationship; D044767:Ubiquitin-Protein Ligases / Q000378:metabolism*
chemical_list: D022763:CCAAT-Enhancer-Binding Protein-alpha; D047908:Intracellular Signaling Peptides and Proteins; D009687:Nuclear Proteins; C515847:tribbles 2 protein, mouse; C471982:COP1 protein, mouse; D044767:Ubiquitin-Protein Ligases; D017346:Protein Serine-Threonine Kinases
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