Regulation of kinetochore and inner-centromere structure and function by the Chromosome Passenger Complex during mitosis 296 views

Mitosis is an important stage in the cell cycle when the duplicated chromosomes are segregated to the daughter cells. Errors in segregation of chromosomes can lead to genomic instability that underlies multiple developmental diseases and cancer. Aurora-B, which is a member of the Chromosome Passenger Complex (CPC), is a key mitotic kinase and plays an important role in ensuring high fidelity mitosis by phosphorylating numerous substrates in the mitotic spindle. Most of the CPC is localized to the inner-centromere during pro-metaphase. This localization of the CPC to the inner-centromere is important for the concentration-dependent autoactivation of the CPC during mitosis. The inner-centromeric CPC also regulates localization of multiple proteins to the inner-centromeres, which are important for proper mitotic progression. How the CPC is maintained in the inner-centromere at high concentration during pro-metaphase and the effect of this high concentration of the CPC on the organization and composition of the inner-centromere are unclear. In Chapter 2, I will show that the liquid-liquid phase separation driven by the centromere-targeting region of the CPC is important for its inner-centromere localization and function and may underlie the mesoscale organization of the innercentromere. Once localized to the inner-centromere the key substrates that Aurora- B phosphorylates to ensure error-free mitosis are often localized 100’s of nm away from the site of peak kinase localization. It is unclear how the activity of the Aurora- B kinase reaches its distant substrates. In Chapter 3, I will describe a mechanism that enables the phosphorylation of distant outer kinetochore substrates by the CPC. I will show that inner-centromeric and microtubule-bound non-inner centromeric 3 CPC cooperate to ensure proper phosphorylation of the outer kinetochore substrates, which is important for correction of improper kinetochore-microtubule attachment. Apart from regulating kinetochore-microtubule attachment Aurora-B also regulates the assembly of the outer kinetochore during mitosis. Aurora-B activity at the kinetochore changes in response to the kinetochore-microtubule attachment status and this change is important for proper mitosis. However, the outer kinetochore organization is thought to remain unchanged before and after kinetochore-microtubule attachment. It is thus unclear if the same interactions underlie the organization of the core outer kinetochore before and after mature kinetochore-microtubule attachment. In Chapter 4, I will present data that suggests that different pathways play a role in the maintenance of the outer kinetochore before and after mature kinetochore-microtubule attachment. I will show that the outer kinetochore maintenance is dependent on the CPC and Plk1 activity before but not after mature kinetochore-microtubule attachment.

PHD (Doctor of Philosophy)

Mitosis ; Chromosome Passenger Complex; kinetochore

English

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2018-07-26