SAS-6 Association with γ-Tubulin Ring Complex Is Required for Centriole Duplication in Human Cells.
Centrioles are essential components of centrosome, the main microtubule-organizing center of animal cells required for robust spindle bipolarity [1, 2]. They are duplicated once during the cell cycle [3], and the duplication involves assembly of a cartwheel on the pre-existing centriole followed by assembly of triplet microtubules around the cartwheel [4, 5]. Although the molecular details of cartwheel formation are understood [6-13], the mechanisms initiating the formation of centriolar microtubules are not known. Here, we show that the central component of cartwheel, HsSAS-6 plays a crucial role in the formation of centriolar microtubules by interacting with the microtubule nucleation machinery, γ-tubulin ring complex (γ-TuRC) in human cells. The globular N terminus and the central coiled-coil domain of SAS-6 are required for formation of the cartwheel [7, 14], whereas the function of its C-terminal outer cartwheel region in centriole duplication remains unclear. We find that deletion of HsSAS-6 C terminus disrupts microtubule formation in daughter centriole, and as a result, cells fail to form the new centriole. Consequently, this results in mitotic cells having only two centrioles localized at a single site. Detailed molecular analyses showed that HsSAS-6 interacts with the γ-TuRC proteins and associates with the γ-TuRC at the centrosome, and furthermore, the C terminus is essential for this association. High-resolution microscopy revealed localization of the γ-TuRC protein, γ-tubulin as multiple lobes surrounding the HsSAS-6-containing central hub in the centriole. Together, the results indicate that HsSAS-6 regulates centriolar microtubule assembly by anchoring γ-TuRCs to the pro-centriole at the onset of daughter centriole formation.
['Gupta|Hindol|H|', 'Rajeev|Resmi|R|', 'Sasmal|Ranjan|R|', 'Radhakrishnan|Renjith M|RM|', 'Anand|Ushma|U|', 'Chandran|Haritha|H|', 'Aparna|Nurni R|NR|', 'Agasti|Sarit|S|', 'Manna|Tapas K|TK|']
D018797:Cell Cycle Proteins D002502:Centrioles D057809:HEK293 Cells D006367:HeLa Cells D006801:Humans D008869:Microtubule-Associated Proteins D001678:Organelle Biogenesis
γ-tubulin centriole microtubule HsSAS-6 mitosis