Telomere loops and homologous recombination-dependent telomeric circles in a Kluyveromyces lactis telomere mutant strain.
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.
Cesare
Anthony J
AJ
Corresonding author. Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA.
Groff-Vindman
Cindy
C
Compton
Sarah A
SA
McEachern
Michael J
MJ
Griffith
Jack D
JD
D001483:Base Sequence; D002850:Chromatography, Gel; D004271:DNA, Fungal / Q000235:genetics; D017353:Gene Deletion; D015966:Gene Expression Regulation, Fungal; D007716:Kluyveromyces / Q000145:classification / Q000235:genetics* / Q000378:metabolism / Q000648:ultrastructure*; D008854:Microscopy, Electron; D008970:Molecular Weight; D009154:Mutation / Q000235:genetics; D010641:Phenotype; D051721:Rad52 DNA Repair and Recombination Protein / Q000235:genetics / Q000378:metabolism; D011995:Recombination, Genetic / Q000235:genetics*; D035182:TATA Box Binding Protein-Like Proteins / Q000235:genetics / Q000378:metabolism; D016615:Telomere / Q000235:genetics* / Q000648:ultrastructure*
D004271:DNA, Fungal; D051721:Rad52 DNA Repair and Recombination Protein; D035182:TATA Box Binding Protein-Like Proteins