THE DYNAMIC CHROMATIN LANDSCAPE IN SACCHAROMYCES CEREVISIAE Public Deposited

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  • March 19, 2019
Creator
  • Tyler, Jolien Suzanne
    • Affiliation: College of Arts and Sciences, Department of Biology
Abstract
  • The accurate and faithful segregation of chromosomes during mitosis is essential for cellular survival. Current paradigms of chromosome segregation focus on the mechanical contributions of the mitotic spindle without considering the biomechanical properties of the chromatin itself. In order to further our understanding of how the inherent physical properties of chromatin contribute to cellular processes like chromosome segregation, we have examined both histone and chromatin dynamics in the budding yeast Saccharomyces cerevisiae. During mitosis, the mitotic spindle exerts force on the pericentromeric chromatin, which adjusts structurally to accommodate this force. By measuring the fluorescence recovery after photobleaching (FRAP), we found that histones are more dynamic in the pericentromeric region as compared to the chromosome arm, and these increased recovery rates are dependent on spindle-based tension. The tension-dependent histone dynamics in the pericentromere are dependent on the chromatin remodeling activities of the Remodels the Structure of Chromatin (RSC) and Imitation Switch (ISWI) ATP-dependent chromatin remodeling complexes. Thus, balanced histone removal and reincorporation in the pericentromere provide a mechanism for accommodation of spindle-based tension and the maintenance of chromatin packaging. Having measured the dynamic nature of histone turnover within the chromatin polymer in response to spindle-based tension, we subsequently examined the spatio-temporal fluctuations of the chromatin polymer. We combined in vivo chromatin motion analysis and mathematical modeling to elucidate the physical properties of the chromatin polymer underlying dynamic fluctuations. The range of chromatin motion and its effective spring constants are found to vary along the length of the chromosome, in a manner dependent on tethering at the centromere. These polymer properties of the chromatin are dependent on both histone occupancy and cohesin packaging. As a whole, the work detailed in this dissertation contributes valuable insights into the importance of dynamic histone occupancy and chromatin motion in defining and maintaining the biomechanical polymer properties of chromosomes in vivo.
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  • In Copyright
Advisor
  • Bloom, Kerry
Degree
  • Doctor of Philosophy
Graduation year
  • 2013
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