"Poisoning" yeast telomeres distinguishes between redundant telomere capping pathways.
In most eukaryotes, telomeres are composed of tandem arrays of species-specific DNA repeats ending with a G-rich 3' overhang. In budding yeast, Cdc13 binds this overhang and recruits Ten1-Stn1 and the telomerase protein Est1 to protect (cap) and elongate the telomeres, respectively. To dissect and study the various pathways employed to cap and maintain the telomere end, we engineered telomerase to incorporate Tetrahymena telomeric repeats (G₄T₂) onto the telomeres of the budding yeast Kluyveromyces lactis. These heterologous repeats caused telomere-telomere fusions, cell cycle arrest at G2/M, and severely reduced viability--the hallmarks of telomere uncapping. Fusing Cdc13 or Est1 to universal minicircle sequence binding protein (UMSBP), a small protein that binds the single-stranded G₄T₂ repeats, rescued the cell viability and restored telomere capping, but not telomerase-mediated telomere maintenance. Surprisingly, Cdc13-UMSBP-mediated telomere capping was dependent on the homologous recombination factor Rad52, while Est1-UMSBP was not. Thus, our results distinguish between two, redundant, telomere capping pathways.
Department of Genetics, The Alexander Silberman Institute of Life Sciences, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Givat Ram, 91904 Jerusalem, Israel.
Noa
N
Lamm
Shhadeh
S
Bsoul
Majdi M
MM
Kabaha
Yehuda
Y
Tzfati
D059447:Cell Cycle Checkpoints / Q000235:genetics; D003001:Cloning, Molecular; D059766:DNA End-Joining Repair / Q000235:genetics; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism*; D007716:Kluyveromyces / Q000166:cytology / Q000235:genetics* / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D011995:Recombination, Genetic; D012091:Repetitive Sequences, Nucleic Acid; D019098:Telomerase / Q000235:genetics / Q000378:metabolism; D016615:Telomere / Q000235:genetics* / Q000378:metabolism*; D034501:Telomere-Binding Proteins / Q000235:genetics / Q000378:metabolism; D013768:Tetrahymena / Q000235:genetics
D005656:Fungal Proteins; D011993:Recombinant Fusion Proteins; D034501:Telomere-Binding Proteins; D019098:Telomerase