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. 2002 Nov;162(3):1101–1115. doi: 10.1093/genetics/162.3.1101

The Est1 subunit of Saccharomyces cerevisiae telomerase makes multiple contributions to telomere length maintenance.

Sara K Evans 1, Victoria Lundblad 1
PMCID: PMC1462332  PMID: 12454059

Abstract

The telomerase-associated Est1 protein of Saccharomyces cerevisiae mediates enzyme access by bridging the interaction between the catalytic core of telomerase and the telomere-binding protein Cdc13. In addition to recruiting telomerase, Est1 may act as a positive regulator of telomerase once the enzyme has been brought to the telomere, as previously suggested by the inability of a Cdc13-Est2 fusion protein to promote extensive telomere elongation in an est1-Delta strain. We report here three classes of mutant Est1 proteins that retain association with the telomerase enzyme but confer different in vivo consequences. Class 1 mutants display a telomere replication defect but are capable of promoting extensive telomere elongation in the presence of a Cdc13-Est2 fusion protein, consistent with a defect in telomerase recruitment. Class 2 mutants fail to elongate telomeres even in the presence of the Cdc13-Est2 fusion, which is the phenotype predicted for a defect in the proposed second regulatory function of EST1. A third class of mutants impairs an activity of Est1 that is potentially required for the Ku-mediated pathway of telomere length maintenance. The isolation of mutations that perturb separate functions of Est1 demonstrates that a telomerase holoenzyme subunit can contribute multiple regulatory roles to telomere length maintenance.

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Selected References

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  1. Bass S. H., Mulkerrin M. G., Wells J. A. A systematic mutational analysis of hormone-binding determinants in the human growth hormone receptor. Proc Natl Acad Sci U S A. 1991 May 15;88(10):4498–4502. doi: 10.1073/pnas.88.10.4498. [DOI] [PMC free article] [PubMed] [Google Scholar]
  2. Cohn M., Blackburn E. H. Telomerase in yeast. Science. 1995 Jul 21;269(5222):396–400. doi: 10.1126/science.7618104. [DOI] [PubMed] [Google Scholar]
  3. Collins K. Mammalian telomeres and telomerase. Curr Opin Cell Biol. 2000 Jun;12(3):378–383. doi: 10.1016/s0955-0674(00)00103-4. [DOI] [PubMed] [Google Scholar]
  4. Counter C. M., Meyerson M., Eaton E. N., Weinberg R. A. The catalytic subunit of yeast telomerase. Proc Natl Acad Sci U S A. 1997 Aug 19;94(17):9202–9207. doi: 10.1073/pnas.94.17.9202. [DOI] [PMC free article] [PubMed] [Google Scholar]
  5. Draper D. E. Themes in RNA-protein recognition. J Mol Biol. 1999 Oct 22;293(2):255–270. doi: 10.1006/jmbi.1999.2991. [DOI] [PubMed] [Google Scholar]
  6. Dubrana K., Perrod S., Gasser S. M. Turning telomeres off and on. Curr Opin Cell Biol. 2001 Jun;13(3):281–289. doi: 10.1016/s0955-0674(00)00210-6. [DOI] [PubMed] [Google Scholar]
  7. Evans S. K., Lundblad V. Est1 and Cdc13 as comediators of telomerase access. Science. 1999 Oct 1;286(5437):117–120. doi: 10.1126/science.286.5437.117. [DOI] [PubMed] [Google Scholar]
  8. Evans S. K., Lundblad V. Positive and negative regulation of telomerase access to the telomere. J Cell Sci. 2000 Oct;113(Pt 19):3357–3364. doi: 10.1242/jcs.113.19.3357. [DOI] [PubMed] [Google Scholar]
  9. Friedman K. L., Cech T. R. Essential functions of amino-terminal domains in the yeast telomerase catalytic subunit revealed by selection for viable mutants. Genes Dev. 1999 Nov 1;13(21):2863–2874. doi: 10.1101/gad.13.21.2863. [DOI] [PMC free article] [PubMed] [Google Scholar]
  10. Gibbs C. S., Zoller M. J. Rational scanning mutagenesis of a protein kinase identifies functional regions involved in catalysis and substrate interactions. J Biol Chem. 1991 May 15;266(14):8923–8931. [PubMed] [Google Scholar]
  11. Hughes T. R., Evans S. K., Weilbaecher R. G., Lundblad V. The Est3 protein is a subunit of yeast telomerase. Curr Biol. 2000 Jun 29;10(13):809–812. doi: 10.1016/s0960-9822(00)00562-5. [DOI] [PubMed] [Google Scholar]
  12. Jones S., Daley D. T., Luscombe N. M., Berman H. M., Thornton J. M. Protein-RNA interactions: a structural analysis. Nucleic Acids Res. 2001 Feb 15;29(4):943–954. doi: 10.1093/nar/29.4.943. [DOI] [PMC free article] [PubMed] [Google Scholar]
  13. Kunkel T. A., Roberts J. D., Zakour R. A. Rapid and efficient site-specific mutagenesis without phenotypic selection. Methods Enzymol. 1987;154:367–382. doi: 10.1016/0076-6879(87)54085-x. [DOI] [PubMed] [Google Scholar]
  14. Lendvay T. S., Morris D. K., Sah J., Balasubramanian B., Lundblad V. Senescence mutants of Saccharomyces cerevisiae with a defect in telomere replication identify three additional EST genes. Genetics. 1996 Dec;144(4):1399–1412. doi: 10.1093/genetics/144.4.1399. [DOI] [PMC free article] [PubMed] [Google Scholar]
  15. Lingner J., Cech T. R., Hughes T. R., Lundblad V. Three Ever Shorter Telomere (EST) genes are dispensable for in vitro yeast telomerase activity. Proc Natl Acad Sci U S A. 1997 Oct 14;94(21):11190–11195. doi: 10.1073/pnas.94.21.11190. [DOI] [PMC free article] [PubMed] [Google Scholar]
  16. Lingner J., Hughes T. R., Shevchenko A., Mann M., Lundblad V., Cech T. R. Reverse transcriptase motifs in the catalytic subunit of telomerase. Science. 1997 Apr 25;276(5312):561–567. doi: 10.1126/science.276.5312.561. [DOI] [PubMed] [Google Scholar]
  17. Livengood April J., Zaug Arthur J., Cech Thomas R. Essential regions of Saccharomyces cerevisiae telomerase RNA: separate elements for Est1p and Est2p interaction. Mol Cell Biol. 2002 Apr;22(7):2366–2374. doi: 10.1128/MCB.22.7.2366-2374.2002. [DOI] [PMC free article] [PubMed] [Google Scholar]
  18. Lundblad V., Szostak J. W. A mutant with a defect in telomere elongation leads to senescence in yeast. Cell. 1989 May 19;57(4):633–643. doi: 10.1016/0092-8674(89)90132-3. [DOI] [PubMed] [Google Scholar]
  19. Marcand S., Brevet V., Mann C., Gilson E. Cell cycle restriction of telomere elongation. Curr Biol. 2000 Apr 20;10(8):487–490. doi: 10.1016/s0960-9822(00)00450-4. [DOI] [PubMed] [Google Scholar]
  20. McEachern M. J., Krauskopf A., Blackburn E. H. Telomeres and their control. Annu Rev Genet. 2000;34:331–358. doi: 10.1146/annurev.genet.34.1.331. [DOI] [PubMed] [Google Scholar]
  21. Morris D. K., Lundblad V. Programmed translational frameshifting in a gene required for yeast telomere replication. Curr Biol. 1997 Dec 1;7(12):969–976. doi: 10.1016/s0960-9822(06)00416-7. [DOI] [PubMed] [Google Scholar]
  22. Nugent C. I., Bosco G., Ross L. O., Evans S. K., Salinger A. P., Moore J. K., Haber J. E., Lundblad V. Telomere maintenance is dependent on activities required for end repair of double-strand breaks. Curr Biol. 1998 May 21;8(11):657–660. doi: 10.1016/s0960-9822(98)70253-2. [DOI] [PubMed] [Google Scholar]
  23. Nugent C. I., Hughes T. R., Lue N. F., Lundblad V. Cdc13p: a single-strand telomeric DNA-binding protein with a dual role in yeast telomere maintenance. Science. 1996 Oct 11;274(5285):249–252. doi: 10.1126/science.274.5285.249. [DOI] [PubMed] [Google Scholar]
  24. O'Reilly M., Teichmann S. A., Rhodes D. Telomerases. Curr Opin Struct Biol. 1999 Feb;9(1):56–65. doi: 10.1016/s0959-440x(99)80008-6. [DOI] [PubMed] [Google Scholar]
  25. Peng Y., Mian I. S., Lue N. F. Analysis of telomerase processivity: mechanistic similarity to HIV-1 reverse transcriptase and role in telomere maintenance. Mol Cell. 2001 Jun;7(6):1201–1211. doi: 10.1016/s1097-2765(01)00268-4. [DOI] [PubMed] [Google Scholar]
  26. Pennock E., Buckley K., Lundblad V. Cdc13 delivers separate complexes to the telomere for end protection and replication. Cell. 2001 Feb 9;104(3):387–396. doi: 10.1016/s0092-8674(01)00226-4. [DOI] [PubMed] [Google Scholar]
  27. Peterson S. E., Stellwagen A. E., Diede S. J., Singer M. S., Haimberger Z. W., Johnson C. O., Tzoneva M., Gottschling D. E. The function of a stem-loop in telomerase RNA is linked to the DNA repair protein Ku. Nat Genet. 2001 Jan;27(1):64–67. doi: 10.1038/83778. [DOI] [PubMed] [Google Scholar]
  28. Prescott J., Blackburn E. H. Telomerase RNA mutations in Saccharomyces cerevisiae alter telomerase action and reveal nonprocessivity in vivo and in vitro. Genes Dev. 1997 Feb 15;11(4):528–540. doi: 10.1101/gad.11.4.528. [DOI] [PubMed] [Google Scholar]
  29. Qi H., Zakian V. A. The Saccharomyces telomere-binding protein Cdc13p interacts with both the catalytic subunit of DNA polymerase alpha and the telomerase-associated est1 protein. Genes Dev. 2000 Jul 15;14(14):1777–1788. [PMC free article] [PubMed] [Google Scholar]
  30. Seto A. G., Zaug A. J., Sobel S. G., Wolin S. L., Cech T. R. Saccharomyces cerevisiae telomerase is an Sm small nuclear ribonucleoprotein particle. Nature. 1999 Sep 9;401(6749):177–180. doi: 10.1038/43694. [DOI] [PubMed] [Google Scholar]
  31. Steiner B. R., Hidaka K., Futcher B. Association of the Est1 protein with telomerase activity in yeast. Proc Natl Acad Sci U S A. 1996 Apr 2;93(7):2817–2821. doi: 10.1073/pnas.93.7.2817. [DOI] [PMC free article] [PubMed] [Google Scholar]
  32. Taggart Andrew K. P., Teng Shu-Chun, Zakian Virginia A. Est1p as a cell cycle-regulated activator of telomere-bound telomerase. Science. 2002 Aug 9;297(5583):1023–1026. doi: 10.1126/science.1074968. [DOI] [PubMed] [Google Scholar]
  33. Virta-Pearlman V., Morris D. K., Lundblad V. Est1 has the properties of a single-stranded telomere end-binding protein. Genes Dev. 1996 Dec 15;10(24):3094–3104. doi: 10.1101/gad.10.24.3094. [DOI] [PubMed] [Google Scholar]
  34. Zhou J., Hidaka K., Futcher B. The Est1 subunit of yeast telomerase binds the Tlc1 telomerase RNA. Mol Cell Biol. 2000 Mar;20(6):1947–1955. doi: 10.1128/mcb.20.6.1947-1955.2000. [DOI] [PMC free article] [PubMed] [Google Scholar]

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