SAS-4 is recruited to a dynamic structure in newly forming centrioles that is stabilized by the gamma-tubulin-mediated addition of centriolar microtubules.
Centrioles are surrounded by pericentriolar material (PCM), which is proposed to promote new centriole assembly by concentrating gamma-tubulin. Here, we quantitatively monitor new centriole assembly in living Caenorhabditis elegans embryos, focusing on the conserved components SAS-4 and SAS-6. We show that SAS-4 and SAS-6 are coordinately recruited to the site of new centriole assembly and reach their maximum levels during S phase. Centriolar SAS-6 is subsequently reduced by a mechanism intrinsic to the early assembly pathway that does not require progression into mitosis. Centriolar SAS-4 remains in dynamic equilibrium with the cytoplasmic pool until late prophase, when it is stably incorporated in a step that requires gamma-tubulin and microtubule assembly. These results indicate that gamma-tubulin in the PCM stabilizes the nascent daughter centriole by promoting microtubule addition to its outer wall. Such a mechanism may help restrict new centriole assembly to the vicinity of preexisting parent centrioles that recruit PCM.
Dammermann
Alexander
A
Department of Cellular and Molecular Medicine, Ludwig Institute for Cancer Research, University of California, San Diego, La Jolla, CA 92093, USA. adammermann@ucsd.edu
Maddox
Paul S
PS
Desai
Arshad
A
Oegema
Karen
K
D000818:Animals; D017173:Caenorhabditis elegans / Q000378:metabolism* / Q000648:ultrastructure; D029742:Caenorhabditis elegans Proteins / Q000378:metabolism*; D018797:Cell Cycle Proteins / Q000378:metabolism; D002454:Cell Differentiation / Q000502:physiology; D002502:Centrioles / Q000378:metabolism* / Q000648:ultrastructure; D004625:Embryo, Nonmammalian / Q000166:cytology / Q000378:metabolism; D046911:Macromolecular Substances / Q000378:metabolism; D008870:Microtubules / Q000378:metabolism* / Q000648:ultrastructure; D021381:Protein Transport / Q000502:physiology; D013045:Species Specificity; D008941:Spindle Apparatus / Q000378:metabolism / Q000648:ultrastructure; D014404:Tubulin / Q000378:metabolism*
D029742:Caenorhabditis elegans Proteins; D018797:Cell Cycle Proteins; D046911:Macromolecular Substances; C472409:SAS-4 protein, C elegans; C497201:SAS-6 protein, C elegans; D014404:Tubulin