LAUSR

Significance Molecular mechanisms that give rise to the remarkable dynamics of the actin and tubulin subunits have been a focus of extensive research. The tightly regulated import/export of tubulin is particularly important for ciliogenesis, given that tubulins form the axoneme “backbone” of all cilia. The interaction with the IFT-74/81 subunits helps load tubulin onto the intraflagellar transport (IFT) machinery for ciliary import. We found that the conserved DYF-5/MAK kinase localizing at the ciliary tip phosphorylates IFT-74, reducing the binding affinity between tubulin and IFT-74/81 sixfold. In vivo manipulation phosphorylation status of IFT-74 changed ciliary length. We propose that DYF-5/MAK–dependent phosphorylation promotes tubulin unloading at the ciliary tip and contributes to site-specific regulation of tubulin dynamics to maintain axonemal integrity.