title: Molecular Mechanism of CCAAT-Enhancer Binding Protein Recruitment by the TRIB1 Pseudokinase.
abstract: CCAAT-enhancer binding proteins (C/EBPs) are transcription factors that play a central role in the differentiation of myeloid cells and adipocytes. Tribbles pseudokinases govern levels of C/EBPs by recruiting them to the COP1 ubiquitin ligase for ubiquitination. Here, we present the first crystal structure of a Tribbles protein, which reveals a catalytically inactive TRIB1 pseudokinase domain with a unique adaptation in the αC helix. A second crystal structure and biophysical studies of TRIB1 with its C-terminal extension, which includes the COP1-binding motif, show that the C-terminal extension is sequestered at a site formed by the modified TRIB1 αC helix. In addition, we have identified and characterized the TRIB1 substrate-recognition sequence within C/EBPα, which is evolutionarily conserved in C/EBP transcription factors. Binding studies indicate that C/EBPα recruitment is weaker in the presence of the C-terminal COP1-binding motif, but the magnitude of this effect suggests that the two bind distinct rather directly overlapping binding sites.
authors.affiliation: The Walter and Eliza Hall Institute of Medical Research, Parkville, VIC 3052, Australia; Department of Medical Biology, University of Melbourne, Parkville, VIC 3052, Australia.
authors.forename: James M
authors.initials: JM
authors.lastname: Murphy
authors.affiliation: Department of Microbiology and Immunology, Otago School of Medical Sciences, University of Otago, PO Box 56, Dunedin 9054, New Zealand.
authors.forename: Yoshio
authors.initials: Y
authors.lastname: Nakatani
authors.affiliation: Biochemistry Department, Otago School of Medical Sciences, University of Otago, PO Box 56, Dunedin 9054, New Zealand.
authors.forename: Sam A
authors.initials: SA
authors.lastname: Jamieson
authors.affiliation: The Walter and Eliza Hall Institute of Medical Research, Parkville, VIC 3052, Australia; Department of Medical Biology, University of Melbourne, Parkville, VIC 3052, Australia.
authors.forename: Weiwen
authors.initials: W
authors.lastname: Dai
authors.affiliation: The Walter and Eliza Hall Institute of Medical Research, Parkville, VIC 3052, Australia; Department of Medical Biology, University of Melbourne, Parkville, VIC 3052, Australia.
authors.forename: Isabelle S
authors.initials: IS
authors.lastname: Lucet
authors.affiliation: Biochemistry Department, Otago School of Medical Sciences, University of Otago, PO Box 56, Dunedin 9054, New Zealand. Electronic address: peter.mace@otago.ac.nz.
authors.forename: Peter D
authors.initials: PD
authors.lastname: Mace
mesh_terms: D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D001665:Binding Sites; D022763:CCAAT-Enhancer-Binding Protein-alpha / Q000737:chemistry / Q000378:metabolism*; D004742:Enhancer Elements, Genetic; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000737:chemistry* / Q000378:metabolism; D008969:Molecular Sequence Data; D011485:Protein Binding; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors* / Q000737:chemistry / Q000378:metabolism
chemical_list: D022763:CCAAT-Enhancer-Binding Protein-alpha; D047908:Intracellular Signaling Peptides and Proteins; C493170:TRIB1 protein, human; D017346:Protein Serine-Threonine Kinases
keywords: C/EBP; CCAAT-enhancer binding protein; COP1; Constitutive Photomorphogenesis Protein 1; DFG motif; Kinase; Pseudokinase; TRIB1; Tribbles