DNA double strand breaks (DSBs) pose a significant threat to a cell's viability and genomic integrity. While several pathways contribute to a cell's response to DSBs, in both plants and animals, the non-homologous end joining (NHEJ) pathway plays an especially important role in their repair. Here I present results demonstrating that while the canonical NHEJ pathway plays an essential role in maintaining genomic integrity in response to both simple and complex DSBs, NHEJ itself is a complex and flexible process that is capable of repairing a wide variety of DSBs.
Using deep-sequencing technology, I was able to demonstrate a role for several DNA repair and cell-cycle checkpoint genes in the repair of DSBs generated via excision of the maize Ac transposable element in Arabidopsis. The sequence data confirms a role for both DNA ligase IV (LIG4) and KU70 in the repair of Ac transposition events. The data also demonstrate that DNA Polymerase Lambda (POLL), DNA ligase VI (LIG6), and the cell-cycle checkpoint genes Ataxia Telangiectasia Mutated (ATM) and Ataxia Telangiectasia mutated and Rad3-related (ATR), are all important in dictating the repair products produced during the repair of Ac excision events. Based on the distribution of Ac excision repair products in wild-type and mutant plants, I propose roles for both LIG6 and POLL in DSB repair.
The effects of radiation with different energetic properties on wild-type and mutant lines was also investigated. I report a two to four fold increase in the relative biological effectiveness of high charge, high energy (HZE) radiation as compared to gamma radiation. In lines deficient for either DNA repair of cell-cycle checkpoint proteins, a significant increase in genomic instability relative to wild-type was observed in response to both HZE and gamma radiation. While ATM and ATR are both important in a cell's response to either HZE or gamma radiation, I report an increase in the importance of ATR relative to ATM in responding to HZE- versus gamma-induced damage.
|Advisor:||Britt, Anne B.|
|Commitee:||Burgess, Sean M., Murphy, Terence M.|
|School:||University of California, Davis|
|School Location:||United States -- California|
|Source:||DAI-B 73/10(E), Dissertation Abstracts International|
|Subjects:||Plant biology, Genetics, Plant sciences|
|Keywords:||Arabidopsis thaliana, DNA double-strand breaks, DNA repair, Ir, Let, Nhej, Transposon|
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