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Unstable Telomere Cap Structures in Saccharomyces cerevisiae yku70 Mutants Cause Altered Cell Cycle Phase Distributions
Author(s) -
Posey Tressie,
Lewis L Kevin
Publication year - 2017
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.31.1_supplement.906.18
Subject(s) - saccharomyces cerevisiae , dna ligase , dna damage , dna repair , dna , microbiology and biotechnology , homologous recombination , biology , cell cycle , non homologous end joining , yeast , genome instability , chemistry , cell , biochemistry
Eukaryotic cells keep their DNA compartmentalized within nuclei, but this does not guard the DNA from damage. There are a number of environmental and intracellular factors such as ionizing radiation, e.g., X‐rays and gamma rays, UV radiation, nucleases, DNA modifying agents, and free radicals that can damage the DNA. One of the most detrimental lesions that can occur in the DNA is a double‐strand break (DSB), where both strands of the double helix are fractured. This damage is the most difficult to repair and holds a number of consequences for the cell's viability. In humans, the main repair pathway for DSBs is NHEJ, or the Nonhomologous End‐Joining pathway. This repair pathway primarily uses three protein complexes to directly rejoin the two broken ends. In Saccharomyces cerevisiae (budding yeast) these three complexes are Mrx (Mre11, Rad50, and Xrs2), DNA ligase IV (Dnl4 and Lif1), and the Ku complex (Yku70 and Yku80). The Ku complex binds to the broken ends first, protecting them from further degradation. Mrx then bridges the gap between the broken ends and DNA ligase IV covalently links the ends together. In this project, yeast yku70 cells, which exhibit a growth defect when grown at 37° C, were analyzed microscopically after growth at multiple temperatures (20° C, 30° C, and 37° C). Normally, yeast cells spend approximately the same proportion of time in G 1 , S, and G 2 /M during log phase growth, but yku70 cells exhibit an increased number of G 2 /M cells. This phenomenon was not seen in other NHEJ mutants such as dnl4 cells. Further experiments involving the quantitation of cells with different nuclear morphologies and testing the role of DNA damage checkpoints will be presented.