Tubulin nucleotide status controls Sas-4-dependent pericentriolar material recruitment

Regulated centrosome biogenesis is required for accurate cell division and for maintaining genome integrity(1). Centrosomes consist of a centriole pair surrounded by a protein network known as pericentriolar material (PCM)(1). PCM assembly is a tightly regulated, critical step that determines a centrosome’s size and capability(2–4). Here, we report a role for tubulin in regulating PCM recruitment via the conserved centrosomal protein Sas-4. Tubulin directly binds to Sas-4; together they are components of cytoplasmic complexes of centrosomal proteins(5,6). A Sas-4 mutant, which cannot bind tubulin, enhances centrosomal protein complex formation and has abnormally large centrosomes with excessive activity. These suggest that tubulin negatively regulates PCM recruitment. Whereas tubulin-GTP prevents Sas-4 from forming protein complexes, tubulin-GDP promotes it. Thus, tubulin’s regulation of PCM recruitment depends on its GTP/GDP-bound state. These results identify a role for tubulin in regulating PCM recruitment independent of its well-known role as a building block of microtubules(7). Based on its guanine bound state, tubulin can act as a molecular switch in PCM recruitment.