Identification and characterization of tac5, a telomerase activation mutant, characterization of DNA damage responses and assessment of interactions between telomere-related proteins in Arabidopsis thaliana /
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| Other Authors: | |
| Format: | Thesis eBook |
| Language: | English |
| Published: |
[College Station, Tex.] :
[Texas A&M University],
[2010]
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| Online Access: | Link to OAK Trust copy |
| Abstract: | Telomerase is a ribonucleoprotein complex that synthesizes telomeric DNA in most eukaryotic organisms. Telomerase expression is highly regulated and the enzyme activity is confined to germline and stem cells in mammals and plants. Utilizing a biochemical screening strategy (TRAP assay) to identify genes regulating telomerase expression in Arabidopsis, activation tagged lines were screened for mutants demonstrating inappropriate expression of telomerase in leaves. As described in chapter II, the mutant tac5 was identified in this screening process and was characterized. Segregation analysis demonstrated that telomerase expression in tac5 is dominant and linked to a complex TDNA insertion. Plasmid rescue showed that tac5 mapped to the right arm of chromosome 5. AtTERT was transcriptionally upregulated in tac5 indicating that telomerase activation in tac5 is either regulated at the transcriptional level or at the post-transcript stabilization level. RT-PCR on genes adjacent to the T-DNA insertion revealed that NADH/Ubiquinone dehydrogenase, which is right next to the T-DNA insertion, is transcriptionally upregulated. Overexpression of this gene in wild type plants conferred telomerase activation in leaves, confirming that NADH/Ubiquinone dehydrogenase is responsible for telomere activation. In addition tac5 showed sensitivity to hydrogen peroxide treatment, suggesting a novel role of telomerase in the mitochondrial environment. Chapter III reports the role of PARP proteins in plant telomere biology. Both AtPARP1 and AtPARP2 are transcriptionally upregulated in response to DNA damage treatment or telomere dysfunction. However, in contrast to mammalian PARPs, the Arabidopsis proteins do not appear to have a function in telomere length maintenance as indicated by TRF analysis or in promoting genome stability maintenance as indicated by cytogenetic studies. Further analysis of PARP interactions at dysfunctional telomeres in the genetically tractable Arabidopsis model may provide insight into the cellular response to dysfunctional telomeres. As explained in chapter IV, the yeast two-hybrid screen was utilized to confirm the interactions of ATR with AtPOT2 and Ku80 and to identify novel interacting partners of Arabidopsis telomere proteins. At2g04410 (Unknown protein) was identified as a direct interacting partner of AtPOT1. This interaction was confirmed in vitro by coimmunoprecipitation assay. Further analysis of the unknown protein may shed light on AtPOT1's function in telomere maintenance. |
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| Item Description: | "Major Subject: Biochemistry" Title from author supplied metadata (automated record created 2010-03-12 12:08:51). Electronic resource. |
| Physical Description: | 1 online resource. |
| Bibliography: | Includes bibliographical references. |