Higher‐order oligomerization promotes localization of SPOP to liquid nuclear speckles

• Melissa R Marzahn ^[1] ; Suresh Marada ^[1] ; Jihun Lee ^[1] ; Amanda Nourse ^[1] ; Sophia Kenrick ^[3] ; Huaying Zhao ^[4] ; Gili Ben‐Nissan ^[5] ; Regina‐Maria Kolaitis ^[1] ; Jennifer L Peters ^[1] ; Stanley Pounds ^[1] ; Wesley J Errington ^[2] ; Gilbert G Privé ^[2] ; J Paul Taylor ^[1] ; Michal Sharon ^[5] ; Peter Schuck ^[4] ; Stacey K Ogden ^[1] ; Tanja Mittag ^[1]
  1. [1] St. Jude Children's Research Hospital

     St. Jude Children's Research Hospital

     Estados Unidos

     
  2. [2] University of Toronto

     University of Toronto

     Canadá

     
  3. [3] 4 Wyatt Technology Corporation Santa Barbara CA USA
  4. [4] 5 Dynamics of Macromolecular Assembly Section Laboratory of Cellular Imaging and Macromolecular Biophysics National Institute of Biomedical Imaging and Bioengineering National Institutes of Health Bethesda MD USA
  5. [5] 6 Department of Biological Chemistry Weizmann Institute of Science Rehovot Israel

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• Localización: EMBO journal: European Molecular Biology Organization, ISSN 0261-4189, Vol. 35, Nº. 12, 2016, págs. 1254-1275
• Idioma: inglés
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  • Membrane‐less organelles in cells are large, dynamic protein/protein or protein/RNA assemblies that have been reported in some cases to have liquid droplet properties. However, the molecular interactions underlying the recruitment of components are not well understood. Herein, we study how the ability to form higher‐order assemblies influences the recruitment of the speckle‐type POZ protein (SPOP) to nuclear speckles. SPOP, a cullin‐3‐RING ubiquitin ligase (CRL3) substrate adaptor, self‐associates into higher‐order oligomers; that is, the number of monomers in an oligomer is broadly distributed and can be large. While wild‐type SPOP localizes to liquid nuclear speckles, self‐association‐deficient SPOP mutants have a diffuse distribution in the nucleus. SPOP oligomerizes through its BTB and BACK domains. We show that BTB‐mediated SPOP dimers form linear oligomers via BACK domain dimerization, and we determine the concentration‐dependent populations of the resulting oligomeric species. Higher‐order oligomerization of SPOP stimulates CRL3SPOP ubiquitination efficiency for its physiological substrate Gli3, suggesting that nuclear speckles are hotspots of ubiquitination. Dynamic, higher‐order protein self‐association may be a general mechanism to concentrate functional components in membrane‐less cellular bodies.