HsSAS-6-dependent cartwheel assembly ensures stabilization of centriole intermediates

Abstract

At the onset of procentriole formation, a structure called the cartwheel is formed adjacent to the pre-existing centriole. SAS-6 proteins are thought to constitute the hub of the cartwheel structure. However, the exact function of the cartwheel in the process of centriole formation has not been well characterized. In this study, we focused on the functions of human SAS-6 (HsSAS-6). Using in vitro reconstitution with recombinant HsSAS-6, we first observed its conserved molecular property forming the central part of the cartwheel structure. Furthermore, we uncovered critical functions of HsSAS-6 using a combination of an auxin-inducible SAS-6-degron system and super-resolution microscopy in human cells. Our results demonstrate that the HsSAS-6 is required not only for the initiation of centriole formation, but also for the stabilization of centriole intermediates. Moreover, after procentriole formation, HsSAS-6 is necessary for limiting Plk4 accumulation at the centrioles and thereby suppressing the formation of potential sites for extra procentrioles. Overall, these findings illustrate the conserved and fundamental functions of the cartwheel in centriole duplication.