CCDC61/VFL3 Is a Paralog of SAS6 and Promotes Ciliary Functions

Takashi Ochi,Valentina Quarantotti,Huawen Lin,Jerome Jullien,Ivan Rosa E Silva,Francesco Boselli,Deepak D Barnabas,Christopher M Johnson,Stephen H Mclaughlin,Stefan M.V Freund,Andrew N Blackford,Yuu Kimata,Raymond E Goldstein,Stephen P Jackson,Tom L Blundell,Susan K Dutcher,Fanni Gergely,Mark Van Breugel

doi:10.1016/j.str.2020.04.010

Abstract

SummaryCentrioles are cylindrical assemblies whose peripheral microtubule array displays a 9-fold rotational symmetry that is established by the scaffolding protein SAS6. Centriole symmetry can be broken by centriole-associated structures, such as the striated fibers in Chlamydomonas that are important for ciliary function. The conserved protein CCDC61/VFL3 is involved in this process, but its exact role is unclear. Here, we show that CCDC61 is a paralog of SAS6. Crystal structures of CCDC61 demonstrate that it contains two homodimerization interfaces that are similar to those found in SAS6, but result in the formation of linear filaments rather than rings. Furthermore, we show that CCDC61 binds microtubules and that residues involved in CCDC61 microtubule binding are important for ciliary function in Chlamydomonas. Together, our findings suggest that CCDC61 and SAS6 functionally diverged from a common ancestor while retaining the ability to scaffold the assembly of basal body-associated structures or centrioles, respectively.

Highlights

Centrosomes are among the largest protein assemblies found in animal cells
We propose that CCDC61/VFL3 plays a role in scaffolding the assembly of basal body-associated structures throughout eukaryotes
CCDC61 Is a Paralog of SAS6 The XRCC4 protein superfamily is constituted by the centriolar protein SAS6 and the DNA repair proteins XRCC4, XLF, and PAXX

Summary

Graphical Abstract

Members of the XRCC4 superfamily of proteins have scaffolding functions in DNA repair or centriole formation. Ochi et al describe the centrosomal protein CCDC61 as a member of this superfamily. CCDC61 oligomerizes and binds to microtubules which plays a role in establishing accessory structures of centrioles in Chlamydomonas. Highlights d CCDC61 is a paralog of SAS6, XRCC4, XLF, and PAXX d CCDC61 can form protofilaments with a 3-fold screw axis in vitro d CCDC61 binds to microtubules mainly via its coiled-coil domain d Microtubule binding of CCDC61 is important for its function in Chlamydomonas. June 2, 2020 a 2020 MRC Laboratory of Molecular Biology

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