eLife Assessment
In their study, Cummings et al. provide a valuable advance in understanding the hierarchical regulation of tubulin polyglycylation, demonstrating that TTLL8 initiates monoglycylation which is a prerequisite for TTLL10-mediated polyglycylation. The evidence supporting these mechanistic insights is solid, relying on a compelling combination of purified biochemical assays, mass spectrometry, and microscopy. The work is further valued for revealing an unexpected crosstalk between polyglycylation and polyglutamylation that ensures a balanced post-translational modification landscape for proper cilia function.