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The Rad51d DNA Repair Gene is Required for Chromosome and Telomore Stability in Mammalian Cells

Smiraldo, Phillip G.
http://rave.ohiolink.edu/etdc/view?acc_num=mco1146675938

Abstract Details

2006, Doctor of Philosophy in Medical Sciences (Ph.D.), University of Toledo, College of Graduate Studies.
The process of homologous genetic recombination is essential for increasing genetic diversity, maintaining chromosome and telomere structure, and repairing DNA damage. A homozygous targeted disruption of Rad51d, a gene required for homologous recombination (HR), confers embryonic and cell lethality in mice. In the absence of Rad51d, elevated levels of genome instability likely result in p53 activation and programmed cell death. As described in this thesis, a p53 deletion is sufficient to extend the lifespan of Rad51d-deficient embryos by up to 6 days, rescue the Rad51d-deficient cell lethal phenotype, and, for the first time, permit the characterization of mammalian cells deficient for Rad51d. The Rad51d-/- Trp53-/- mouse embryonic fibroblasts (MEFs) exhibited extensive chromosome instability including aneuploidy, chromosome fragments, deletions, and complex rearrangements. Additionally, loss of Rad51d resulted in increased levels of centrosome fragmentation, which is likely a consequence of mitotic catastrophe initiated by chromosome instability in the mutant cells. Consistent with the role of RAD51D in HR-mediated repair of DNA damage, Rad51d-deficient cells were hypersensitive to DNA-damaging agents, particularly interstrand crosslinks, had reduced levels of radiation-induced RAD51-focus formation, and had decreased levels of DNA damage-induced sister chromatid exchange. These findings support a crucial role for the RAD51D protein in normal development, recombination, and DNA repair. In addition to its role in DNA repair, the RAD51D protein localizes at telomeres, DNA-protein structures that protect chromosome ends. Decreased telomere lengths and increased levels of anaphase bridging and telomere fusions were observed in primary Rad51d-deficient cells. Additionally, telomeres in the Rad51d-/- Trp53-/- MEFs had an increased frequency of being detected as DNA damage, as determined by the telomeric localization of γ-H2AX foci, and had long single-stranded telomeric 3´ overhangs. These data demonstrate that RAD51D functions to protect telomeres against attrition and fusion, potentially by assisting in the formation or resolution of telomeric T-loop structures. The novel findings presented here and the tools that have been generated lay the groundwork for continued investigations to determine the mechanistic roles of RAD51D in maintaining genome stability, which may underlie protection against carcinogenesis.
Douglas Pittman, Ph.D. (Advisor)
319 p.
DNA Repair; Homologous Recombination; Telomere

Recommended Citations

Citations

  • Smiraldo, P. G. (2006). The Rad51d DNA Repair Gene is Required for Chromosome and Telomore Stability in Mammalian Cells [Doctoral dissertation, University of Toledo]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=mco1146675938

    APA Style (7th edition)

  • Smiraldo, Phillip. The Rad51d DNA Repair Gene is Required for Chromosome and Telomore Stability in Mammalian Cells. 2006. University of Toledo, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=mco1146675938.

    MLA Style (8th edition)

  • Smiraldo, Phillip. "The Rad51d DNA Repair Gene is Required for Chromosome and Telomore Stability in Mammalian Cells." Doctoral dissertation, University of Toledo, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=mco1146675938

    Chicago Manual of Style (17th edition)

mco1146675938
939
© 2006, all rights reserved.
This open access ETD is published by University of Toledo Health Science Campus and OhioLINK.