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Dissertation
Ku80 facilitates chromatin binding of the telomere-binding protein TRF2 and enhances genomic stability in normal human fibroblasts
Doctor of Philosophy (Ph.D.), Drexel University
Jul 2010
DOI:
https://doi.org/10.17918/00007957
Abstract
The Ku heterodimer is central to non-homologous end joining repair, the predominant pathway in mammals for repair of DNA double-strand breaks. The heterodimer, consisting of Ku70 and Ku80, has also been implicated in chromosome stability and telomere maintenance, and the Ku80 gene appears to be essential for human but not rodent cell survival. Ku associates with a number of proteins involved in various processes, including replication, cell adhesion, and transcription. The diversity of Ku interactions suggests the requirements for Ku in the cell may extend beyond canonical repair. While the role of the Ku heterodimer in DNA repair and immune function are well established, the role of Ku80 in processes beyond DNA end joining, including telomere biology, are not fully understood. Targeting Ku80 leads to a number of telomeric effects that differ somewhat depending on the cell type, suggesting Ku may be differentially required for telomere stability. In order to examine in more detail the role of Ku80 in normal human cells, we have utilized RNA interference using a human fibroblast strain. Following targeted Ku80 knockdown, WI38 fibroblasts undergo rapid growth arrest and display characteristics of senescence with evidence of non-disjunction and telomere abnormalities. The growth arrest and senescence activation seem to be at least partially mediated by p53. In addition, levels of TRF2, a sequence-specific telomere binding protein, are reduced following loss of Ku80, suggesting a critical role for Ku in maintaining the telomere protein complex. Our results suggest that the Ku heterodimer enhances TRF2 chromatin association and that non-chromatin bound TRF2 is targeted to the proteasome. Taking into consideration these novel results as well as the reported functions and ubiquitous expression of Ku, we propose a fundamental role for the Ku heterodimer as a docking site for TRF2 at the telomere. We also address the potential role for Ku in species-specific responses to damaged chromatin, suggesting a novel function for Ku in cellular communication. The enhanced association of a sequence-specific DNA binding protein through association with the Ku heterodimer provides a potential model to explain the requirement for Ku in multiple cellular processes.
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Details
- Title
- Ku80 facilitates chromatin binding of the telomere-binding protein TRF2 and enhances genomic stability in normal human fibroblasts
- Creators
- Lauren Sara Koltowski Fink
- Contributors
- Christian Sell (Advisor) - Drexel University, Drexel University (1970-)
- Awarding Institution
- Drexel University
- Degree Awarded
- Doctor of Philosophy (Ph.D.)
- Publisher
- Drexel University; Philadelphia, Pennsylvania
- Number of pages
- xi, 182 pages
- Resource Type
- Dissertation
- Language
- English
- Academic Unit
- Drexel University
- Other Identifier
- 991021888891904721