Centriolar SAS-5 is required for centrosome duplication in C. elegans

Abstract

Centrosomes, the major microtubule-organizing centres (MTOCs) of animal cells, are comprised of a pair of centrioles surrounded by pericentriolar material (PCM). Early in the cell cycle, there is a single centrosome, which duplicates during S-phase to direct bipolar spindle assembly during mitosis¹. Although crucial for proper cell division, the mechanisms that govern centrosome duplication are not fully understood. Here, we identify the Caenorhabditis elegans gene sas-5 as essential for daughter-centriole formation. SAS-5 is a coiled-coil protein that localizes primarily to centrioles. Fluorescence recovery after photobleaching (FRAP) experiments with green fluorescent protein (GFP) fused to SAS-5 (GFP–SAS-5) demonstrated that the protein shuttles between centrioles and the cytoplasm throughout the cell cycle. Analysis of mutant alleles revealed that the presence of SAS-5 at centrioles is crucial for daughter-centriole formation and that ZYG-1, a kinase that is also essential for this process², controls the distribution of SAS-5 to centrioles. Furthermore, partial RNA-interference (RNAi)-mediated inactivation experiments suggest that both sas-5 and zyg-1 are dose-dependent regulators of centrosome duplication.