Kinetochore-microtubule attachments are strengthened by Cnn1 stabilization of Stu2

Cnn1 (CENP-T) purifications sustain dynamic, load-bearing kinetochore–microtubule attachments, and a conserved N-terminal tail mutation weakens attachment strength and causes a growth defect when Dsn1 is impaired.

• Why it matters: Robust chromosome segregation depends on kinetochore–microtubule attachments that resist load while tracking microtubule dynamics, but Cnn1’s biophysical contribution to this stability was unclear.
• What they did: Using an optical trapping-based assay, the study tested Cnn1-purified complexes under load; it then introduced a conserved N-terminal tail mutation, measured attachment strength, and assessed kinetochore protein levels, focusing on Stu2.
• The result: The Cnn1 mutation reduced Stu2 kinetochore levels without changing other kinetochore proteins, and restoring Stu2 in vitro or tethering it to Ndc80c in vivo rescued attachment strength and cellular viability.

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