Abstract
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 (G 4T2) 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 G4T 2 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.
| Original language | English |
|---|---|
| Pages (from-to) | 613-627 |
| Number of pages | 15 |
| Journal | Chromosoma |
| Volume | 121 |
| Issue number | 6 |
| DOIs | |
| State | Published - Dec 2012 |
Bibliographical note
Funding Information:Acknowledgments This work was supported by the Israel Science Foundation grant 1355/08, the German–Israeli Foundation grant I-849-253.13/2004, and the United States–Israel Binational Science Foundation grant 2009204. We thank Yde Steensma for the GG1634 and GG1935 K. lactis strains, Joseph Shlomai for the UMSBP1 construct and for stimulating discussions, Tommer Ravid for his assistance with measuring growth rates, and Raphael Falk and Noa Gil for critical reviewing of the manuscript.