Telomere loops and homologous recombination-dependent telomeric circles in a Kluyveromyces lactis telomere mutant strain |
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Authors: | Cesare Anthony J Groff-Vindman Cindy Compton Sarah A McEachern Michael J Griffith Jack D |
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Institution: | Corresonding author. Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA. |
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Abstract: | The Kluyveromyces lactis ter1-16T strain contains mutant telomeres that are poorly bound by Rap1, resulting in a telomere-uncapping phenotype and significant elongation of the telomeric DNA. The elongated telomeres of ter1-16T allowed the isolation and examination of native yeast telomeric DNA by electron microscopy. In the telomeric DNA isolated from ter1-16T, looped molecules were observed with the physical characteristics of telomere loops (t-loops) previously described in mammalian and plant cells. ter1-16T cells were also found to contain free circular telomeric DNA molecules (t-circles) ranging up to the size of an entire telomere. When the ter1-16T uncapping phenotype was repressed by overexpression of RAP1 or recombination was inhibited by deletion of rad52, the isolated telomeric DNA contained significantly fewer t-loops and t-circles. These results suggest that disruption of Rap1 results in elevated recombination at telomeres, leading to increased strand invasion of the 3′ overhang within t-loop junctions and resolution of the t-loop junctions into free t-circles. |
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