The TPR-containing domain within Est1 homologs exhibits species-specific roles in telomerase interaction and telomere length homeostasis

Springer Science and Business Media LLC - Tập 12 - Trang 1-15 - 2011
David CF Sealey1, Aleksandar D Kostic1,2, Catherine LeBel1,3, Fiona Pryde4, Lea Harrington1,4,5
1Department of Medical Biophysics, University of Toronto; Campbell Family Institute for Breast Cancer Research and Ontario Cancer Institute, University Health Network, Toronto, Canada
2Department of Pathology, Harvard Medical School, Boston, USA
3Department of Pathology, Samuel Lunenfeld Research Institute, Mount Sinai Hospital, Toronto, Canada
4Wellcome Trust Centre for Cell Biology, University of Edinburgh, Edinburgh, UK
5Université de Montréal, Institute de Recherche en Immunologie et en Cancérologie, Montréal, Canada

Tóm tắt

The first telomerase-associated protein (Est1) was isolated in yeast due to its essential role in telomere maintenance. The human counterparts EST1A, EST1B, and EST1C perform diverse functions in nonsense-mediated mRNA decay (NMD), telomere length homeostasis, and telomere transcription. Although Est1 and EST1A/B interact with the catalytic subunit of yeast and human telomerase (Est2 and TERT, respectively), the molecular determinants of these interactions have not been elaborated fully. To investigate the functional conservation of the EST1 protein family, we performed protein-protein interaction mapping and structure-function analysis. The domain in hEST1A most conserved between species, containing a TPR (tricotetrapeptide repeat), was sufficient for interaction of hEST1A with multiple fragments of hTERT including the N-terminus. Two mutations within the hTERT N-terminus that perturb in vivo function (NAAIRS92, NAAIRS122) did not affect this protein interaction. ScEst1 hybrids containing the TPR of hEST1A, hEST1B, or hEST1C were expressed in yeast strains lacking EST1, yet they failed to complement senescence. Point mutations within and outside the cognate ScEst1 TPR, chosen to disrupt a putative protein interaction surface, resulted in telomere lengthening or shortening without affecting recruitment to telomeres. These results identify a domain encompassing the TPR of hEST1A as an hTERT interaction module. The TPR of S. cerevisiae Est1 is required for telomerase-mediated telomere length maintenance in a manner that appears separable from telomere recruitment. Discrete residues in or adjacent to the TPR of Est1 also regulate telomere length homeostasis.

Tài liệu tham khảo

Lundblad V, Szostak JW: A mutant with a defect in telomere elongation leads to senescence in yeast. Cell. 1989, 57 (4): 633-643. 10.1016/0092-8674(89)90132-3 Lendvay TS, Morris DK, Sah J, Balasubramanian B, Lundblad V: Senescence mutants of Saccharomyces cerevisiae with a defect in telomere replication identify three additional EST genes. Genetics. 1996, 144 (4): 1399-1412. Weinert TA, Hartwell LH: Cell cycle arrest of cdc mutants and specificity of the RAD9 checkpoint. Genetics. 1993, 134 (1): 63-80. Grandin N, Charbonneau M: Telomerase- and Rad52-independent immortalization of budding yeast by an inherited-long-telomere pathway of telomeric repeat amplification. Mol Cell Biol. 2009, 29 (4): 965-985. 10.1128/MCB.00817-08 Le S, Moore JK, Haber JE, Greider CW: RAD50 and RAD51 define two pathways that collaborate to maintain telomeres in the absence of telomerase. Genetics. 1999, 152 (1): 143-152. Lebel C, Rosonina E, Sealey DC, Pryde F, Lydall D, Maringele L, Harrington LA: Telomere maintenance and survival in saccharomyces cerevisiae in the absence of telomerase and RAD52. Genetics. 2009, 182 (3): 671-684. 10.1534/genetics.109.102939 Lee JY, Mogen JL, Chavez A, Johnson FB: Sgs1 RecQ helicase inhibits survival of Saccharomyces cerevisiae cells lacking telomerase and homologous recombination. J Biol Chem. 2008, 283 (44): 29847-29858. 10.1074/jbc.M804760200 Lundblad V, Blackburn EH: An alternative pathway for yeast telomere maintenance rescues est1- senescence. Cell. 1993, 73 (2): 347-360. 10.1016/0092-8674(93)90234-H Maringele L, Lydall D: Telomerase- and recombination-independent immortalization of budding yeast. Genes Dev. 2004, 18 (21): 2663-2675. 10.1101/gad.316504 Teng SC, Zakian VA: Telomere-telomere recombination is an efficient bypass pathway for telomere maintenance in Saccharomyces cerevisiae. Mol Cell Biol. 1999, 19 (12): 8083-8093. Evans SK, Lundblad V: Positive and negative regulation of telomerase access to the telomere. J Cell Sci. 2000, 113 (Pt 19): 3357-3364. Vega LR, Mateyak MK, Zakian VA: Getting to the end: telomerase access in yeast and humans. Nat Rev Mol Cell Biol. 2003, 4 (12): 948-959. Taggart AK, Zakian VA: Telomerase: what are the Est proteins doing?. Curr Opin Cell Biol. 2003, 15 (3): 275-280. 10.1016/S0955-0674(03)00040-1 Smogorzewska A, de Lange T: Regulation of telomerase by telomeric proteins. Annu Rev Biochem. 2004, 73: 177-208. 10.1146/annurev.biochem.73.071403.160049 Nugent CI, Hughes TR, Lue NF, Lundblad V: Cdc13p: a single-strand telomeric DNA-binding protein with a dual role in yeast telomere maintenance. Science. 1996, 274 (5285): 249-252. 10.1126/science.274.5285.249 Lin JJ, Zakian VA: The Saccharomyces CDC13 protein is a single-strand TG1-3 telomeric DNA-binding protein in vitro that affects telomere behavior in vivo. Proc Natl Acad Sci USA. 1996, 93 (24): 13760-13765. 10.1073/pnas.93.24.13760 Taggart AK, Teng SC, Zakian VA: Est1p as a cell cycle-regulated activator of telomere-bound telomerase. Science. 2002, 297 (5583): 1023-1026. 10.1126/science.1074968 Fisher TS, Taggart AK, Zakian VA: Cell cycle-dependent regulation of yeast telomerase by Ku. Nat Struct Mol Biol. 2004, 11 (12): 1198-1205. 10.1038/nsmb854 Virta-Pearlman V, Morris DK, Lundblad V: Est1 has the properties of a single-stranded telomere end-binding protein. Genes Dev. 1996, 10 (24): 3094-3104. 10.1101/gad.10.24.3094 Schramke V, Luciano P, Brevet V, Guillot S, Corda Y, Longhese MP, Gilson E, Geli V: RPA regulates telomerase action by providing Est1p access to chromosome ends. Nat Genet. 2004, 36 (1): 46-54. 10.1038/ng1284 Qi H, Zakian VA: 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, 14 (14): 1777-1788. Evans SK, Lundblad V: Est1 and Cdc13 as comediators of telomerase access. Science. 1999, 286 (5437): 117-120. 10.1126/science.286.5437.117 Pennock E, Buckley K, Lundblad V: Cdc13 delivers separate complexes to the telomere for end protection and replication. Cell. 2001, 104 (3): 387-396. 10.1016/S0092-8674(01)00226-4 Lin JJ, Zakian VA: An in vitro assay for Saccharomyces telomerase requires EST1. Cell. 1995, 81 (7): 1127-1135. 10.1016/S0092-8674(05)80017-0 Steiner BR, Hidaka K, Futcher B: Association of the Est1 protein with telomerase activity in yeast. Proc Natl Acad Sci USA. 1996, 93 (7): 2817-2821. 10.1073/pnas.93.7.2817 Zhou J, Hidaka K, Futcher B: The Est1 subunit of yeast telomerase binds the Tlc1 telomerase RNA. Mol Cell Biol. 2000, 20 (6): 1947-1955. 10.1128/MCB.20.6.1947-1955.2000 Livengood AJ, Zaug AJ, Cech TR: Essential regions of Saccharomyces cerevisiae telomerase RNA: separate elements for Est1p and Est2p interaction. Mol Cell Biol. 2002, 22 (7): 2366-2374. 10.1128/MCB.22.7.2366-2374.2002 Seto AG, Livengood AJ, Tzfati Y, Blackburn EH, Cech TR: A bulged stem tethers Est1p to telomerase RNA in budding yeast. Genes Dev. 2002, 16 (21): 2800-2812. 10.1101/gad.1029302 Chan A, Boule JB, Zakian VA: Two pathways recruit telomerase to Saccharomyces cerevisiae telomeres. PLoS Genet. 2008, 4 (10): e1000236- 10.1371/journal.pgen.1000236 Beernink HT, Miller K, Deshpande A, Bucher P, Cooper JP: Telomere maintenance in fission yeast requires an est1 ortholog. Curr Biol. 2003, 13 (7): 575-580. 10.1016/S0960-9822(03)00169-6 Singh SM, Steinberg-Neifach O, Mian IS, Lue NF: Analysis of telomerase in Candida albicans: potential role in telomere end protection. Eukaryot Cell. 2002, 1 (6): 967-977. 10.1128/EC.1.6.967-977.2002 Reichenbach P, Hoss M, Azzalin CM, Nabholz M, Bucher P, Lingner J: A human homolog of yeast Est1 associates with telomerase and uncaps chromosome ends when overexpressed. Curr Biol. 2003, 13 (7): 568-574. 10.1016/S0960-9822(03)00173-8 Snow BE, Erdmann N, Cruickshank J, Goldman H, Gill RM, Robinson MO, Harrington L: Functional conservation of the telomerase protein Est1p in humans. Curr Biol. 2003, 13 (8): 698-704. 10.1016/S0960-9822(03)00210-0 Azzalin CM, Reichenbach P, Khoriauli L, Giulotto E, Lingner J: Telomeric repeat containing RNA and RNA surveillance factors at mammalian chromosome ends. Science. 2007, 318 (5851): 798-801. 10.1126/science.1147182 Chiu SY, Serin G, Ohara O, Maquat LE: Characterization of human Smg5/7a: a protein with similarities to Caenorhabditis elegans SMG5 and SMG7 that functions in the dephosphorylation of Upf1. Rna. 2003, 9 (1): 77-87. 10.1261/rna.2137903 Clissold PM, Ponting CP: PIN domains in nonsense-mediated mRNA decay and RNAi. Curr Biol. 2000, 10 (24): R888-890. 10.1016/S0960-9822(00)00858-7 Gatfield D, Unterholzner L, Ciccarelli FD, Bork P, Izaurralde E: Nonsense-mediated mRNA decay in Drosophila: at the intersection of the yeast and mammalian pathways. EMBO J. 2003, 22 (15): 3960-3970. 10.1093/emboj/cdg371 Ohnishi T, Yamashita A, Kashima I, Schell T, Anders KR, Grimson A, Hachiya T, Hentze MW, Anderson P, Ohno S: Phosphorylation of hUPF1 induces formation of mRNA surveillance complexes containing hSMG-5 and hSMG-7. Mol Cell. 2003, 12 (5): 1187-1200. 10.1016/S1097-2765(03)00443-X Maquat LE: Nonsense-mediated mRNA decay: splicing, translation and mRNP dynamics. Nat Rev Mol Cell Biol. 2004, 5 (2): 89-99. Behm-Ansmant I, Kashima I, Rehwinkel J, Sauliere J, Wittkopp N, Izaurralde E: mRNA quality control: an ancient machinery recognizes and degrades mRNAs with nonsense codons. FEBS Lett. 2007, 581 (15): 2845-2853. 10.1016/j.febslet.2007.05.027 Paillusson A, Hirschi N, Vallan C, Azzalin CM, Muhlemann O: A GFP-based reporter system to monitor nonsense-mediated mRNA decay. Nucleic Acids Res. 2005, 33 (6): e54- 10.1093/nar/gni052 Luke B, Azzalin CM, Hug N, Deplazes A, Peter M, Lingner J: Saccharomyces cerevisiae Ebs1p is a putative ortholog of human Smg7 and promotes nonsense-mediated mRNA decay. Nucleic Acids Res. 2007, 35 (22): 7688-7697. 10.1093/nar/gkm912 Luke B, Lingner J: TERRA: telomeric repeat-containing RNA. EMBO J. 2009, 28 (17): 2503-2510. 10.1038/emboj.2009.166 Dahlseid JN, Lew-Smith J, Lelivelt MJ, Enomoto S, Ford A, Desruisseaux M, McClellan M, Lue N, Culbertson MR, Berman J: mRNAs encoding telomerase components and regulators are controlled by UPF genes in Saccharomyces cerevisiae. Eukaryot Cell. 2003, 2 (1): 134-142. 10.1128/EC.2.1.134-142.2003 Blatch GL, Lassle M: The tetratricopeptide repeat: a structural motif mediating protein-protein interactions. Bioessays. 1999, 21 (11): 932-939. 10.1002/(SICI)1521-1878(199911)21:11<932::AID-BIES5>3.0.CO;2-N Fukuhara N, Ebert J, Unterholzner L, Lindner D, Izaurralde E, Conti E: SMG7 is a 14-3-3-like adaptor in the nonsense-mediated mRNA decay pathway. Mol Cell. 2005, 17 (4): 537-547. 10.1016/j.molcel.2005.01.010 Redon S, Reichenbach P, Lingner J: Protein RNA and protein protein interactions mediate association of human EST1A/SMG6 with telomerase. Nucleic Acids Res. 2007, 35 (20): 7011-7022. 10.1093/nar/gkm724 Lundblad V: Telomere replication: an est fest. Curr Biol. 2003, 13 (11): R439-441. 10.1016/S0960-9822(03)00365-8 Glavan F, Behm-Ansmant I, Izaurralde E, Conti E: Structures of the PIN domains of SMG6 and SMG5 reveal a nuclease within the mRNA surveillance complex. EMBO J. 2006, 25 (21): 5117-5125. 10.1038/sj.emboj.7601377 Eberle AB, Lykke-Andersen S, Muhlemann O, Jensen TH: SMG6 promotes endonucleolytic cleavage of nonsense mRNA in human cells. Nat Struct Mol Biol. 2009, 16 (1): 49-55. 10.1038/nsmb.1530 Sealey DCF: Regulation of Telomerase by DNA and Protein Interactions. 2010, Toronto: University of Toronto Armbruster BN, Banik SS, Guo C, Smith AC, Counter CM: N-terminal domains of the human telomerase catalytic subunit required for enzyme activity in vivo. Mol Cell Biol. 2001, 21 (22): 7775-7786. 10.1128/MCB.21.22.7775-7786.2001 Banik SS, Guo C, Smith AC, Margolis SS, Richardson DA, Tirado CA, Counter CM: C-terminal regions of the human telomerase catalytic subunit essential for in vivo enzyme activity. Mol Cell Biol. 2002, 22 (17): 6234-6246. 10.1128/MCB.22.17.6234-6246.2002 Lee SR, Wong JM, Collins K: Human telomerase reverse transcriptase motifs required for elongation of a telomeric substrate. J Biol Chem. 2003, 278 (52): 52531-52536. 10.1074/jbc.M311359200 Moriarty TJ, Ward RJ, Taboski MA, Autexier C: An anchor site-type defect in human telomerase that disrupts telomere length maintenance and cellular immortalization. Mol Biol Cell. 2005, 16 (7): 3152-3161. 10.1091/mbc.E05-02-0148 Sealey DC, Zheng L, Taboski MA, Cruickshank J, Ikura M, Harrington LA: The N-terminus of hTERT contains a DNA-binding domain and is required for telomerase activity and cellular immortalization. Nucleic Acids Res. 2009 Armbruster BN, Etheridge KT, Broccoli D, Counter CM: Putative telomere-recruiting domain in the catalytic subunit of human telomerase. Mol Cell Biol. 2003, 23 (9): 3237-3246. 10.1128/MCB.23.9.3237-3246.2003 Armbruster BN, Linardic CM, Veldman T, Bansal NP, Downie DL, Counter CM: Rescue of an hTERT mutant defective in telomere elongation by fusion with hPot1. Mol Cell Biol. 2004, 24 (8): 3552-3561. 10.1128/MCB.24.8.3552-3561.2004 Rothstein R: Targeting, Disruption, Replacement, and Allele Rescue: Integrative DNA Transformation in Yeast. Guide to Yeast Genetics and Molecular Biology. Edited by: Guthrie C, Fink GR. 1991, 281-301. San Diego, CA: Academic Press Evans SK, Lundblad V: The Est1 Subunit of Saccharomyces cerevisiae Telomerase Makes Multiple Contributions to Telomere Length Maintenance. Genetics. 2002, 162 (3): 1101-1115. Arai K, Masutomi K, Khurts S, Kaneko S, Kobayashi K, Murakami S: Two independent regions of human telomerase reverse transcriptase are important for its oligomerization and telomerase activity. J Biol Chem. 2002, 277 (10): 8538-8544. 10.1074/jbc.M111068200 Beattie TL, Zhou W, Robinson MO, Harrington L: Functional multimerization of the human telomerase reverse transcriptase. Mol Cell Biol. 2001, 21 (18): 6151-6160. 10.1128/MCB.21.18.6151-6160.2001 Moriarty TJ, Marie-Egyptienne DT, Autexier C: Functional organization of repeat addition processivity and DNA synthesis determinants in the human telomerase multimer. Mol Cell Biol. 2004, 24 (9): 3720-3733. 10.1128/MCB.24.9.3720-3733.2004 Zaug AJ, Podell ER, Nandakumar J, Cech TR: Functional interaction between telomere protein TPP1 and telomerase. Genes Dev. 2010, 24 (6): 613-622. 10.1101/gad.1881810 Jurczyluk J, Nouwens AS, Holien JK, Adams TE, Lovrecz GO, Parker MW, Cohen SB, Bryan TM: Direct involvement of the TEN domain at the active site of human telomerase. Nucleic Acids Res. 2010, 39 (5): 1774-1788. Robart AR, Collins K: Human Telomerase Domain Interactions Capture DNA for TEN Domain-Dependent Processive Elongation. Mol Cell. 2011, 42 (3): 308-318. 10.1016/j.molcel.2011.03.012 Rosenfeld KK, Ziv T, Goldin S, Glaser F, Manor H: Mapping of DNA Binding Sites in the Tetrahymena Telomerase Holoenzyme Proteins by UV Cross-Linking and Mass Spectrometry. J Mol Biol. 2011 Steczkiewicz K, Zimmermann MT, Kurcinski M, Lewis BA, Dobbs D, Kloczkowski A, Jernigan RL, Kolinski A, Ginalski K: Human telomerase model shows the role of the TEN domain in advancing the double helix for the next polymerization step. Proc Natl Acad Sci USA. 2011 Hughes TR, Evans SK, Weilbaecher RG, Lundblad V: The Est3 protein is a subunit of yeast telomerase. Curr Biol. 2000, 10 (13): 809-812. 10.1016/S0960-9822(00)00562-5 DeZwaan DC, Freeman BC: The conserved Est1 protein stimulates telomerase DNA extension activity. Proc Natl Acad Sci USA. 2009, 106 (41): 17337-17342. 10.1073/pnas.0905703106 Kang SS, Kwon T, Kwon DY, Do SI: Akt protein kinase enhances human telomerase activity through phosphorylation of telomerase reverse transcriptase subunit. J Biol Chem. 1999, 274 (19): 13085-13090. 10.1074/jbc.274.19.13085 Kharbanda S, Kumar V, Dhar S, Pandey P, Chen C, Majumder P, Yuan ZM, Whang Y, Strauss W, Pandita TK, et al.: Regulation of the hTERT telomerase catalytic subunit by the c-Abl tyrosine kinase. Curr Biol. 2000, 10 (10): 568-575. 10.1016/S0960-9822(00)00483-8 Lamb JR, Michaud WA, Sikorski RS, Hieter PA: Cdc16p, Cdc23p and Cdc27p form a complex essential for mitosis. Embo J. 1994, 13 (18): 4321-4328. Yu EY, Steinberg-Neifach O, Dandjinou AT, Kang F, Morrison AJ, Shen X, Lue NF: Regulation of telomere structure and functions by subunits of the INO80 chromatin remodeling complex. Mol Cell Biol. 2007, 27 (16): 5639-5649. 10.1128/MCB.00418-07 Bochman ML, Sabouri N, Zakian VA: Unwinding the functions of the Pif1 family helicases. DNA Repair (Amst). 2010, 9 (3): 237-249. 10.1016/j.dnarep.2010.01.008. O'Rourke TW, Doudican NA, Zhang H, Eaton JS, Doetsch PW, Shadel GS: Differential involvement of the related DNA helicases Pif1p and Rrm3p in mtDNA point mutagenesis and stability. Gene. 2005, 354: 86-92. Cheng X, Qin Y, Ivessa AS: Loss of mitochondrial DNA under genotoxic stress conditions in the absence of the yeast DNA helicase Pif1p occurs independently of the DNA helicase Rrm3p. Mol Genet Genomics. 2009, 281 (6): 635-645. 10.1007/s00438-009-0438-6 Pinter SF, Aubert SD, Zakian VA: The Schizosaccharomyces pombe Pfh1p DNA helicase is essential for the maintenance of nuclear and mitochondrial DNA. Mol Cell Biol. 2008, 28 (21): 6594-6608. 10.1128/MCB.00191-08 Ryu GH, Tanaka H, Kim DH, Kim JH, Bae SH, Kwon YN, Rhee JS, MacNeill SA, Seo YS: Genetic and biochemical analyses of Pfh1 DNA helicase function in fission yeast. Nucleic Acids Res. 2004, 32 (14): 4205-4216. 10.1093/nar/gkh720 Tanaka H, Ryu GH, Seo YS, Tanaka K, Okayama H, MacNeill SA, Yuasa Y: The fission yeast pfh1(+) gene encodes an essential 5' to 3' DNA helicase required for the completion of S-phase. Nucleic Acids Res. 2002, 30 (21): 4728-4739. 10.1093/nar/gkf590 Zhou JQ, Qi H, Schulz VP, Mateyak MK, Monson EK, Zakian VA: Schizosaccharomyces pombe pfh1+ encodes an essential 5' to 3' DNA helicase that is a member of the PIF1 subfamily of DNA helicases. Mol Biol Cell. 2002, 13 (6): 2180-2191. 10.1091/mbc.02-02-0021 Mateyak MK, Zakian VA: Human PIF helicase is cell cycle regulated and associates with telomerase. Cell Cycle. 2006, 5 (23): 2796-2804. 10.4161/cc.5.23.3524 Snow BE, Mateyak M, Paderova J, Wakeham A, Iorio C, Zakian V, Squire J, Harrington L: Murine Pif1 interacts with telomerase and is dispensable for telomere function in vivo. Mol Cell Biol. 2007, 27 (3): 1017-1026. 10.1128/MCB.01866-06 Reynolds GE, Gao Q, Miller D, Snow BE, Harrington LA, Murnane JP: PIF1 disruption or NBS1 hypomorphism does not affect chromosome healing or fusion resulting from double-strand breaks near telomeres in murine embryonic stem cells. DNA Repair (Amst). 2011 Kanoh J, Ishikawa F: spRap1 and spRif1, recruited to telomeres by Taz1, are essential for telomere function in fission yeast. Curr Biol. 2001, 11 (20): 1624-1630. 10.1016/S0960-9822(01)00503-6 Levy DL, Blackburn EH: Counting of Rif1p and Rif2p on Saccharomyces cerevisiae telomeres regulates telomere length. Mol Cell Biol. 2004, 24 (24): 10857-10867. 10.1128/MCB.24.24.10857-10867.2004 Teixeira MT, Arneric M, Sperisen P, Lingner J: Telomere length homeostasis is achieved via a switch between telomerase- extendible and -nonextendible states. Cell. 2004, 117 (3): 323-335. 10.1016/S0092-8674(04)00334-4 Miller KM, Ferreira MG, Cooper JP: Taz1, Rap1 and Rif1 act both interdependently and independently to maintain telomeres. Embo J. 2005, 24 (17): 3128-3135. 10.1038/sj.emboj.7600779 Castano I, Pan SJ, Zupancic M, Hennequin C, Dujon B, Cormack BP: Telomere length control and transcriptional regulation of subtelomeric adhesins in Candida glabrata. Mol Microbiol. 2005, 55 (4): 1246-1258. Adams IR, McLaren A: Identification and characterisation of mRif1: a mouse telomere-associated protein highly expressed in germ cells and embryo-derived pluripotent stem cells. Dev Dyn. 2004, 229 (4): 733-744. 10.1002/dvdy.10471 Buonomo SB, Wu Y, Ferguson D, de Lange T: Mammalian Rif1 contributes to replication stress survival and homology-directed repair. J Cell Biol. 2009, 187 (3): 385-398. 10.1083/jcb.200902039 Silverman J, Takai H, Buonomo SB, Eisenhaber F, de Lange T: Human Rif1, ortholog of a yeast telomeric protein, is regulated by ATM and 53BP1 and functions in the S-phase checkpoint. Genes Dev. 2004, 18 (17): 2108-2119. 10.1101/gad.1216004 Xu L, Blackburn EH: Human Rif1 protein binds aberrant telomeres and aligns along anaphase midzone microtubules. J Cell Biol. 2004, 167 (5): 819-830. 10.1083/jcb.200408181 Riehs N, Akimcheva S, Puizina J, Bulankova P, Idol RA, Siroky J, Schleiffer A, Schweizer D, Shippen DE, Riha K: Arabidopsis SMG7 protein is required for exit from meiosis. J Cell Sci. 2008, 121 (Pt 13): 2208-2216. Oulton R, Harrington L: A human telomerase-associated nuclease. Mol Biol Cell. 2004, 15 (7): 3244-3256. 10.1091/mbc.E04-03-0178 Sikorski RS, Hieter P: A system of shuttle vectors and yeast host strains designed for efficient manipulation of DNA in Saccharomyces cerevisiae. Genetics. 1989, 122 (1): 19-27. Christianson TW, Sikorski RS, Dante M, Shero JH, Hieter P: Multifunctional yeast high-copy-number shuttle vectors. Gene. 1992, 110 (1): 119-122. 10.1016/0378-1119(92)90454-W Amberg D, Burke D, Strathern J: Methods in Yeast Genetics. 2005, Cold Spring Harbor, New York: Cold Spring Harbor Laboratory Press LeBel C, Larrivee M, Bah A, Laterreur N, Lvesque N, Wellinger RJ: Assessing telomeric phenotypes. Methods Mol Biol. 2006, 313: 265-316. Turchin A, Lawler JF: The primer generator: a program that facilitates the selection of oligonucleotides for site-directed mutagenesis. Biotechniques. 1999, 26 (4): 672-676. Evans PM, Liu C: SiteFind: a software tool for introducing a restriction site as a marker for successful site-directed mutagenesis. BMC Mol Biol. 2005, 6: 22- 10.1186/1471-2199-6-22