Genes required to maintain telomeres in the absence of telomerase in Saccharomyces cerevisiae

Alotaibi, Mohammad Kdaimes H. (2012) Genes required to maintain telomeres in the absence of telomerase in Saccharomyces cerevisiae. PhD thesis, University of Nottingham.

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Abstract

In the absence of telomerase, Saccharomyces cerevisiae telomeres erode leading to senescence. Rare cells can survive after this stage as they can elongate their telomeres utilizing homologous recombination. Two different types of survivors can be easily distinguished by Southern blot. Type I survivor cells, elongate the telomere by amplifying Y elements and require RAD51, RAD54, RAD55 and RAD57 for establishment. Type II survivors elongate their telomere by amplifying TG1-3 repeats, however, they require the following genes to be established: RAD50, MRE11 and XRS2, RAD59, SGS1 and KU80 in some cases. Both types require the gene RAD52.

In this study several candidate genes were deleted individually in diploid type II survivor strains. The main aim of this work was to see if these genes were required for type II telomere maintenance. Most of these genes are not required for type II telomere maintenance at least until ~150 generations after deleting these genes. The exceptions were KU80 and RPB9. Ku80Δ strains switched to a new survivor type that is similar to type I and continued for the long term. RPB9 was required for two independent type II survivor strains to survive, whereas the third type II strain did not require this gene at ~150 generations after deleting the gene. After many generations (~ 350), this strain switched to type I.

At long term propagation (~500 generations) after deletion of the candidate genes, all type II strains displayed telomere shortening until the propagation was stopped. However, Rad50Δ strains switched to type I after long term.

Finally, the absence of the candidate genes did not affect the sensitivity of type II survivor strains to temperature. On the other hand, type II survivor strains with some genes deleted displayed sensitivity to UV.

Item Type: Thesis (University of Nottingham only) (PhD)
Supervisors: Louis, E.
Subjects: Q Science > QH Natural history. Biology
QS-QZ Preclinical sciences (NLM Classification) > QU Biochemistry
Faculties/Schools: UK Campuses > Faculty of Medicine and Health Sciences > School of Biology
Item ID: 12589
Depositing User: EP, Services
Date Deposited: 23 Nov 2012 11:01
Last Modified: 15 Sep 2016 09:00
URI: http://eprints.nottingham.ac.uk/id/eprint/12589

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