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SAS-4 is recruited to a dynamic structure in newly forming centrioles that is stabilized by the γ-tubulin–mediated addition of centriolar microtubules

2008; Rockefeller University Press; Volume: 180; Issue: 4 Linguagem: Inglês

10.1083/jcb.200709102

1540-8140

Alexander Dammermann, Paul S. Maddox, Arshad Desai, Karen Oegema,

Plant Molecular Biology Research

Centrioles are surrounded by pericentriolar material (PCM), which is proposed to promote new centriole assembly by concentrating γ-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 γ-tubulin and microtubule assembly. These results indicate that γ-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.