SAS-6 Assembly Templated by the Lumen of Cartwheel-less Centrioles Precedes Centriole Duplication

• SAS-6 is recruited to the proximal lumen of mother centrioles in early S phase
• SAS-6 is organized into a cartwheel-like configuration by the centriole lumen
• Release of luminal SAS-6 from mother centrioles requires PLK4 and STIL
• Centriole engagement/disengagement regulates luminal recruitment of SAS-6

SummaryCentrioles are 9-fold symmetric structures duplicating once per cell cycle. Duplication involves self-oligomerization of the centriolar protein SAS-6, but how the 9-fold symmetry is invariantly established remains unclear. Here, we found that SAS-6 assembly can be shaped by preexisting (or mother) centrioles. During S phase, SAS-6 molecules are first recruited to the proximal lumen of the mother centriole, adopting a cartwheel-like organization through interactions with the luminal wall, rather than via their self-oligomerization activity. The removal or release of luminal SAS-6 requires Plk4 and the cartwheel protein STIL. Abolishing either the recruitment or the removal of luminal SAS-6 hinders SAS-6 (or centriole) assembly at the outside wall of mother centrioles. After duplication, the lumen of engaged mother centrioles becomes inaccessible to SAS-6, correlating with a block for reduplication. These results lead to a proposed model that centrioles may duplicate via a template-based process to preserve their geometry and copy number.