Methylation of MATCAP by PRMT5 regulates microtubule detyrosination to ensure mitotic fidelity

During mitosis, motor protein-driven chromosome motility is essential for faithful chromosome segregation. The tubulin code, comprising tubulin isotypes and post-translational modifications, guides motor proteins along microtubules. Recent studies show that MATCAP-mediated α-tubulin detyrosination guides proper chromosome congression and segregation during mitosis. However, the mechanisms of action underlying MATCAP activity regulation remain poorly understood. Here, we identify PRMT5 as a novel MATCAP methyl-transferase and that the methylation guides MATCAP activity for chromosome alignment. PRMT5 depletion or inhibition impairs chromosome alignment and segregation. Biochemical analyses reveal that MATCAP interacts with PRMT5 and is a bona fide substrate of PRMT5. Our mass spectrometry analyses show that PRMT5 symmetrically dimethylates the N-terminus of MATCAP at Arg74, Arg99, and Arg104. Importantly, the PRMT5-elicited methylation attenuates MATCAP's microtubule-binding and detyrosination activities. Loss of PRMT5 or expression of non-methylatable MATCAP mutants causes excessive tubulin detyrosination and disrupts chromosome congression. These findings suggest that PRMT5-mediated dynamic methylation of MATCAP is a novel regulatory mechanism that guides accurate tyrosination and ensures mitotic fidelity.