Garcia-Rodriguez, L. J. | bioRxiv Science

bioRxiv2023

Aurora B spatial separation from its outer kinetochore substrates stabilizes chromosome biorientation when tension is applied

For correct chromosome segregation in mitosis, sister kinetochores must interact with microtubules from opposite spindle poles (biorientation). For this, aberrant kinetochore- microtubule interaction must be resolved (error correction) by Aurora B kinase. Once biorientation is formed, tension is applied across sister kinetochores, stabilizing kinetochore- microtubule interactions. The mechanism for this tension-dependent process has been debated. Here we study how localizations of Aurora B at different kinetochore sites affect the establishment and maintenance of biorientation in budding yeast. In the absence of the physiological Aurora B-INCENP recruitment mechanisms, engineered recruitment of Aurora B-INCENP to the inner kinetochore (Mif2) prior to biorientation supports the subsequent establishment of biorientation. By contrast, an engineered Aurora B-INCENP recruitment to the outer kinetochore (Ndc80) fails to support biorientation establishment. Furthermore, when the physiological Aurora B-INCENP recruitment mechanisms are present, an engineered Aurora B-INCENP recruitment to Mif2 during metaphase (after biorientation establishment) does not affect biorientation maintenance. By contrast, an engineered Aurora B-INCENP recruitment to Ndc80 during metaphase leads to disruption of biorientation, which is dependent on the kinase activity of Aurora B. Taken together, our results suggest that spatial separation of Aurora B from its outer kinetochore substrates is required to stabilize kinetochore-microtubule interaction when biorientation is formed and tension is applied on this interaction. Meanwhile, Aurora B shows dynamic turnover (or exchange) on the centromere and kinetochore during early mitosis. It has been thought that this turnover is crucial for error correction and biorientation, as it may help Aurora B reach its substrates in distance and/or may facilitate the Aurora B activation on the mitotic spindle. However, using the engineered Aurora B-INCENP recruitment to the inner kinetochore, we demonstrate that, even without such a turnover, Aurora B-INCENP can efficiently support biorientation. Altogether, our study provides important insights into how Aurora B promotes error correction and biorientation in a tension-dependent manner.

cell biology↗

bioRxiv2019

Aurora B-INCENP localization at centromeres/inner kinetochores is essential for chromosome bi-orientation in budding yeast

To promote chromosome bi-orientation, Aurora B kinase weakens and disrupts aberrant kinetochore-MT interaction. It has long been debated how Aurora B halts this action when bi-orientation is established and tension is applied across sister kinetochores. Pertinent to this debate, it was shown that Bir1 (yeast Survivin), which recruits Ipl1-Sli15 (yeast Aurora B-INCENP) to centromeres, is dispensable for bi-orientation, raising the possibility that Aurora B localization at centromeres is not required for bi-orientation. Here, we show that the COMA inner kinetochore sub-complex physically interacts with Sli15, recruits Ipl1-Sli15 to the inner kinetochore and promotes chromosome bi-orientation, independently of Bir1, in budding yeast. Moreover, using an engineered recruitment of Ipl1-Sli15 to the inner kinetochore when both Bir1 and COMA are defective, we show that localization of Ipl1-Sli15 at centromeres/inner kinetochores is essential for bi-orientation, refuting the above possibility. Our results give important insight into how Aurora B disrupts kinetochore-MT interaction in a tension-dependent manner, to promote chromosome bi-orientation.

cell biology↗