Regulation of Kinetochore Function in Anaphase

Kinetochores mediate interactions between DNA and microtubules during cell division and are essential for proper chromosome segregation. Over 100 human kinetochore components have been identified, but the mechanisms by which these proteins and the kinetochore as a whole adapt their molecular properties to fulfill the changing requirements for chromosome segregation are poorly understood. By comparing the molecular differences between metaphase and anaphase kinetochores and assessing kinetochore functionality by monitoring chromosome movement, I will identify the molecular factors that determine the kinetochore`s ability to segregate sister chromatids. First, I will deplete selected kinetochore proteins to identify the molecular components required for chromosome segregation. Using specialized fusion proteins, I will also eliminate specific proteins acutely in anaphase bypassing their earlier mitotic function and analyze their isolated anaphase function. Second, I will analyze the changes in kinetochore composition and phosphorylation status at anaphase onset and monitor the consequences of disrupting these changes using: (1) specific chemical kinase inhibitors; (2) altered kinase localization and activity; and (3) phosphatase inhibition. My analysis will provide a better understanding of how kinetochores are modified between metaphase and anaphase to segregate the genome accurately.

This study provides insights into how the genetic material is physically passed down from mother to daughter cells. For an organism to grow, its number of cells needs to increase. This increase takes place through cell division in which a mother cell splits into two daughter cells. Before cell division occurs, the mother cell creates two complete copies of its genetic information so that both daughter cells have all the necessary information. Chromosomes carry that genetic information and define the characteristics of an individual, and so must be distributed correctly to the daughter cells. In this study I focused on the mechanical distribution of chromosomes. This process takes place in a particular step of cell division called anaphase. In anaphase, chromosomes move to opposite sides within the dividing cell leading to physical separation of the two copies of the genetic information before a division. Surprisingly, although cell division is a fundamental process, I found that chromosome movement varies by cell type. Our study also revealed that a master regulatory system uses a chemical process called phosphorylation to modify chromosome movement. This process is particularly important for the correct timing to coordinate when chromosomes move towards opposing sides of the dividing cell. This work has furthered our understanding of how mechanistically the genetic material is inherited. Our findings are also of particular interest for potential therapeutic targeting of diseases such as cancer, where errors often occur during the process of cell division.