Microtubule tyrosination/detyrosination specifies a mitotic error code

Incorrect kinetochore-microtubule attachments during mitosis can lead to chromosomal instability, a hallmark of human cancers. Mitotic error correction relies on the kinesin-13 MCAK, a microtubule depolymerase whose activity in vitro is suppressed by alpha-tubulin detyrosination - a post-translational modification enriched on long-lived microtubules. However, whether and how MCAK activity required for mitotic error correction is regulated by microtubule tyrosination/detyrosination remains unknown. Here we found that microtubule detyrosination accumulates on correct, more stable, kinetochore-microtubule attachments, whereas constitutively high microtubule detyrosination near kinetochores compromised efficient error correction. Rescue experiments suggest that mitotic errors due to excessive microtubule detyrosination result from suppression of MCAK activity, without globally affecting kinetochore microtubule half-life. Importantly, MCAK centromeric activity was required and sufficient to rescue mitotic errors due to excessive microtubule detyrosination. Thus, microtubules are not just passive elements during mitotic error correction, and their tyrosination/detyrosination works as a mitotic error code that allows centromeric MCAK to discriminate correct and incorrect kinetochore-microtubule attachments, thereby promoting mitotic fidelity.