Hec1 Tail Phosphorylation Differentially Regulates Mammalian Kinetochore Coupling to Polymerizing and Depolymerizing...

Chromosome segregation during mitosis depends on kinetochore interactions with microtubules. These interactions involve both polymerizing and depolymerizing microtubules, which are essential for chromosome congression and segregation. While the molecular components of kinetochore binding are increasingly understood, the physical mechanisms governing interactions with different microtubule states remain unclear. Active interfaces transduce microtubule depolymerization into mechanical work, while passive interfaces generate friction. However, the role of specific proteins like Hec1 in these interactions is not fully understood. Aurora B phosphorylation regulates Hec1's affinity for microtubules, but its impact on polymerizing versus depolymerizing microtubules is unknown. This gap motivates a closer examination of Hec1's role in kinetochore mechanics.

This study aims to clarify how Hec1 tail phosphorylation influences kinetochore coupling to polymerizing and depolymerizing microtubules. The authors seek to determine whether Hec1's regulation is differential between these two microtubule states. By focusing on Hec1's mechanical role, the research addresses a key question in mitotic regulation. The study's motivation stems from the lack of clarity regarding how kinetochores interact with microtubules in different dynamic states. The authors propose to use laser ablation to decouple sister kinetochores in vivo and observe the effects of Hec1 tail phosphorylation. This approach allows for a direct comparison of Hec1's function on polymerizing versus depolymerizing microtubules. The goal is to uncover how phosphorylation tunes kinetochore behavior during mitosis.

The authors employed laser ablation to induce cellular pulling on mutant kinetochores in mammalian cells. This technique allowed them to decouple sister kinetochores and observe their interactions with microtubules in vivo. They focused on the Hec1 protein, which is known to be phosphorylated by Aurora B on its N-terminal tail. The study involved analyzing the effects of Hec1 tail phosphorylation on microtubule coupling. The researchers used live-cell imaging to track kinetochore behavior following ablation. They also assessed the mechanical role of Hec1 in maintaining grip on microtubules. The experimental design enabled separate probing of Hec1's role on polymerizing and depolymerizing microtubules. The data collection included measurements of kinetochore movement and microtubule interactions.

The study found that Hec1 tail phosphorylation modulates friction along polymerizing microtubules without affecting the kinetochore's grip on depolymerizing microtubules. Laser ablation revealed that mutant kinetochores with altered Hec1 tail phosphorylation exhibited differential behavior. Specifically, phosphorylation reduced the friction on polymerizing microtubules but did not impair the kinetochore's ability to grip depolymerizing microtubules. The data suggest that Hec1's regulation is state-specific, with distinct effects on microtubule dynamics. The authors observed that phosphorylated Hec1 allows for smoother movement along growing microtubules. However, this modification does not compromise the kinetochore's ability to maintain tension on shrinking microtubules. These findings indicate that Hec1 tail phosphorylation serves as a regulatory mechanism for kinetochore coupling. The results highlight the importance of Hec1 in modulating microtubule interactions during mitosis.

The authors conclude that Hec1 tail phosphorylation differentially regulates kinetochore coupling to polymerizing and depolymerizing microtubules. Their findings suggest that phosphorylation tunes friction on growing microtubules without compromising grip on shrinking ones. This mechanism allows the kinetochore to modulate its interactions with microtubules during mitosis. The data support the idea that kinetochore regulation is state-specific. The authors propose that this differential regulation enables the kinetochore to retain its ability to couple to microtubules powering chromosome movement. The study's results align with the hypothesis that Hec1's phosphorylation serves as a mechanical regulator. The authors emphasize that their findings provide insight into how kinetochores adapt to microtubule dynamics. These conclusions are based on the observed effects of Hec1 tail phosphorylation in mammalian cells.