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Nat Commun. 2017 Mar 23;8:14813. doi: 10.1038/ncomms14813.

Cell-free reconstitution reveals centriole cartwheel assembly mechanisms.

Author information

1
Swiss Institute for Experimental Cancer Research (ISREC), School of Life Sciences, Swiss Federal Institute of Technology (EPFL), Lausanne CH-1015, Switzerland.
2
Department of Cell Biology, Sciences III, University of Geneva, Geneva CH-1211, Switzerland.
3
Institute of Anatomy, University of Bern, Bern CH-3012, Switzerland.
4
Center for Cellular Imaging and NanoAnalytics (C-CINA), Biozentrum, University of Basel, Basel CH-4058, Switzerland.
5
Institut Curie, PSL Research University, UMR 168, Centre de Recherche, 26 rue d'ULM, Paris 75231, France.

Abstract

How cellular organelles assemble is a fundamental question in biology. The centriole organelle organizes around a nine-fold symmetrical cartwheel structure typically ∼100 nm high comprising a stack of rings that each accommodates nine homodimers of SAS-6 proteins. Whether nine-fold symmetrical ring-like assemblies of SAS-6 proteins harbour more peripheral cartwheel elements is unclear. Furthermore, the mechanisms governing ring stacking are not known. Here we develop a cell-free reconstitution system for core cartwheel assembly. Using cryo-electron tomography, we uncover that the Chlamydomonas reinhardtii proteins CrSAS-6 and Bld10p together drive assembly of the core cartwheel. Moreover, we discover that CrSAS-6 possesses autonomous properties that ensure self-organized ring stacking. Mathematical fitting of reconstituted cartwheel height distribution suggests a mechanism whereby preferential addition of pairs of SAS-6 rings governs cartwheel growth. In conclusion, we have developed a cell-free reconstitution system that reveals fundamental assembly principles at the root of centriole biogenesis.

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