title: Functional role of TRIM E3 ligase oligomerization and regulation of catalytic activity.
abstract: TRIM E3 ubiquitin ligases regulate a wide variety of cellular processes and are particularly important during innate immune signalling events. They are characterized by a conserved tripartite motif in their N-terminal portion which comprises a canonical RING domain, one or two B-box domains and a coiled-coil region that mediates ligase dimerization. Self-association via the coiled-coil has been suggested to be crucial for catalytic activity of TRIMs; however, the precise molecular mechanism underlying this observation remains elusive. Here, we provide a detailed characterization of the TRIM ligases TRIM25 and TRIM32 and show how their oligomeric state is linked to catalytic activity. The crystal structure of a complex between the TRIM25 RING domain and an ubiquitin-loaded E2 identifies the structural and mechanistic features that promote a closed E2~Ub conformation to activate the thioester for ubiquitin transfer allowing us to propose a model for the regulation of activity in the full-length protein. Our data reveal an unexpected diversity in the self-association mechanism of TRIMs that might be crucial for their biological function.
authors.affiliation: Mill Hill Laboratory, Molecular Structure of Cell Signalling Laboratory, The Francis Crick Institute, London, UK.
authors.forename: Marios G
authors.initials: MG
authors.lastname: Koliopoulos
authors.affiliation: Mill Hill Laboratory, Molecular Structure of Cell Signalling Laboratory, The Francis Crick Institute, London, UK.
authors.forename: Diego
authors.initials: D
authors.lastname: Esposito
authors.affiliation: Structural Biology Science Technology Platform, The Francis Crick Institute, London, UK.
authors.forename: Evangelos
authors.initials: E
authors.lastname: Christodoulou
authors.affiliation: Mill Hill Laboratory, Macromolecular Structure Laboratory, The Francis Crick Institute, London, UK.
authors.forename: Ian A
authors.initials: IA
authors.lastname: Taylor
authors.affiliation: Mill Hill Laboratory, Molecular Structure of Cell Signalling Laboratory, The Francis Crick Institute, London, UK katrin.rittinger@crick.ac.uk.
authors.forename: Katrin
authors.identifier: 0000-0002-7698-4435
authors.initials: K
authors.lastname: Rittinger
mesh_terms: D003460:Crystallization; D006801:Humans; D011487:Protein Conformation; D055503:Protein Multimerization; D014157:Transcription Factors / Q000737:chemistry* / Q000378:metabolism*; D000070584:Tripartite Motif Proteins / Q000737:chemistry* / Q000378:metabolism*; D044767:Ubiquitin-Protein Ligases / Q000737:chemistry* / Q000378:metabolism*; D054875:Ubiquitination
chemical_list: D014157:Transcription Factors; D000070584:Tripartite Motif Proteins; C084523:TRIM25 protein, human; C094027:TRIM32 protein, human; D044767:Ubiquitin-Protein Ligases
keywords: TRIM25; TRIM32; enzyme mechanism; protein structure; ubiquitin ligase