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. 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. Consequently, this results in mitotic cells having only two centrioles localized at a single site.
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. The globular N terminus and the central coiled-coil domain of SAS-6 are required for formation of the cartwheel, whereas the function of its C-terminal outer cartwheel region in centriole duplication remains unclear. 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. Although the molecular details of cartwheel formation are understood, the mechanisms initiating the formation of centriolar microtubules are not known. They are duplicated once during the cell cycle, and the duplication involves assembly of a cartwheel on the pre-existing centriole followed by assembly of triplet microtubules around the cartwheel. In Microsoft Outlook 2010, select the SAS tab in the Ribbon. In the Tools group, click Help and select Help for SAS Add-In for Microsoft Office. Centrioles are essential components of centrosome, the main microtubule-organizing center of animal cells required for robust spindle bipolarity. When SAS Add-In for Microsoft Office is installed, the Help is accessible in the following ways: In Microsoft Office 2010, or 2007, select the SAS tab in the Ribbon.