| Summary: | <p>Centrioles are microtubule-based organelles that organise the microtubule network and seed the formation of cilia and flagella. New centrioles assemble through a step-wise process dependent notably on the centriolar protein SAS-5 in <i>Caenorhabditis elegans</i>. SAS-5 and its functional homologues in other species form oligomers that bind the centriolar proteins SAS-6 and SAS-4, thereby forming an evolutionarily conserved structural core at the onset of organelle assembly. Here, we report a novel interaction of SAS-5 with microtubules. Microtubule binding requires SAS-5 oligomerisation and a disordered protein segment that overlaps with the SAS-4 binding site. Combined <i>in vitro</i> and <i>in vivo</i> analysis of select mutants reveals that the SAS-5–microtubule interaction facilitates centriole assembly in C. elegans embryos. Our findings lead us to propose that the interdependence of SAS-5 oligomerisation and microtubule binding reflects an avidity mechanism that strengthens SAS-5 associations with other centriole components and, thus, promotes organelle assembly.</p>
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