Direct Binding of SAS-6 to ZYG-1 Recruits SAS-6 to the Mother Centriole for Cartwheel Assembly

摘要

Assembly of SAS-6 dimers to form the centriolar cartwheel requires the ZYG-1/Plk4 kinase. Here, we show that ZYG-1 recruits SAS-6 to the mother centriole independently of its kinase activity; kinase activity is subsequently required for cartwheel assembly. We identify a direct interaction between ZYG-1 and the SAS-6 coiled coil that explains its kinase activity-independent function in SAS-6 recruitment. Perturbing this interaction, or the interaction between an adjacent segment of the SAS-6 coiled coil and SAS-5, prevented SAS-6 recruitment and cartwheel assembly. SAS-6 mutants with alanine substitutions in a previously described ZYG-1 target site or in 37 other residues, either phosphorylated by ZYG-1 invitro or conserved in closely related nematodes, all supported cartwheel assembly. We propose that ZYG-1 binding to the SAS-6 coiled coil recruits the SAS-6-SAS-5 complex to the mother centriole, where a ZYG-1 kinase activity-dependent step, whose target is unlikely to be SAS-6, triggers cartwheel assembly. ?SAS-6 recruitment to the mother centriole and cartwheel assembly are separable events?Direct binding of ZYG-1 to the SAS-6 coiled coil recruits SAS-6 to the assembly site?ZYG-1 kinase activity is required for cartwheel assembly but not SAS-6 recruitment?SAS-6 is unlikely to be a critical ZYG-1 kinase substrate during cartwheel assembly.