Kannan, Kalpana (2008-12). Characterization of telomerase RNP in Arabidopsis thaliana. Doctoral Dissertation. Thesis uri icon

abstract

  • Telomeres are critical for the integrity of eukaryotic genomes. They function to protect chromosome ends from DNA damage surveillance and inappropriate repair. Telomeres are maintained by the specialized ribonucleoprotein complex telomerase. Without telomerase, telomere shortening would ultimately lead to compromised genome stability and cellular senescence. Therefore, telomerase function is necessary for extension of the proliferative capacity of the cell. In this dissertation, we describe the characterization of core components of telomerase ribonucleoprotein complex in the flowering plant, Arabidopsis thaliana. We find that dyskerin, one of the core telomerase components in humans is also conserved in Arabidopsis telomerase. Arabidopsis dyskerin associates with the telomerase RNP in an RNA-dependent manner and is required for telomere length maintenance in this organism. We also describe the characterization of another core telomerase component, the telomerase RNA subunits (TERs). Unexpectedly, we uncovered two distinct TER subunits that share a region of high identity. The two TERs named TER1G7 and TER5G2, based on their chromosomal positions, display differences in their expression levels and their association with telomere-related proteins. Both TERs can serve as templates for telomerase in vitro. Through genetic analyses, we show a templating function for TER1G7 in vivo and a novel role for TER5G2 as a negative regulator of telomerase. Finally, the presence of TER genes in other plant species was investigated and evidence for duplication of TER genes in plants closely related to Arabidopsis was obtained. We also show evidence for a template mutation in Asparagus TER that could lead to variant repeats in this organism. In summary, the studies presented in this dissertation reveal that Arabidopsis telomerase shares both similarities and differences with other telomerase RNPs, making it an exciting model system for study of telomere biology.
  • Telomeres are critical for the integrity of eukaryotic genomes. They function to
    protect chromosome ends from DNA damage surveillance and inappropriate repair.
    Telomeres are maintained by the specialized ribonucleoprotein complex telomerase.
    Without telomerase, telomere shortening would ultimately lead to compromised genome
    stability and cellular senescence. Therefore, telomerase function is necessary for
    extension of the proliferative capacity of the cell.
    In this dissertation, we describe the characterization of core components of
    telomerase ribonucleoprotein complex in the flowering plant, Arabidopsis thaliana. We
    find that dyskerin, one of the core telomerase components in humans is also conserved
    in Arabidopsis telomerase. Arabidopsis dyskerin associates with the telomerase RNP in
    an RNA-dependent manner and is required for telomere length maintenance in this
    organism. We also describe the characterization of another core telomerase component,
    the telomerase RNA subunits (TERs). Unexpectedly, we uncovered two distinct TER
    subunits that share a region of high identity. The two TERs named TER1G7 and TER5G2,
    based on their chromosomal positions, display differences in their expression levels and
    their association with telomere-related proteins. Both TERs can serve as templates for
    telomerase in vitro. Through genetic analyses, we show a templating function for TER1G7 in vivo and a novel role for TER5G2 as a negative regulator of telomerase. Finally, the
    presence of TER genes in other plant species was investigated and evidence for
    duplication of TER genes in plants closely related to Arabidopsis was obtained. We also
    show evidence for a template mutation in Asparagus TER that could lead to variant
    repeats in this organism.
    In summary, the studies presented in this dissertation reveal that Arabidopsis
    telomerase shares both similarities and differences with other telomerase RNPs, making
    it an exciting model system for study of telomere biology.

publication date

  • December 2008