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Pif1- and Exo1-dependent nucleases coordinate checkpoint activation following telomere uncapping

Lookup NU author(s): James Dewar, Professor David Lydall

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Abstract

Essential telomere 'capping' proteins act as a safeguard against ageing and cancer by inhibiting the DNA damage response (DDR) and regulating telomerase recruitment, thus distinguishing telomeres from double-strand breaks (DSBs). Uncapped telomeres and unrepaired DSBs can both stimulate a potent DDR, leading to cell cycle arrest and cell death. Using the cdc13-1 mutation to conditionally 'uncap' telomeres in budding yeast, we show that the telomere capping protein Cdc13 protects telomeres from the activity of the helicase Pif1 and the exonuclease Exo1. Our data support a two-stage model for the DDR at uncapped telomeres; Pif1 and Exo1 resect telomeric DNA <5 kb from the chromosome end, stimulating weak checkpoint activation; resection is extended >5kb by Exo1 and full checkpoint activation occurs. Cdc13 is also crucial for telomerase recruitment. However, cells lacking Cdc13, Pif1 and Exo1, do not senesce and maintain their telomeres in a manner dependent upon telomerase, Ku and homologous recombination. Thus, attenuation of the DDR at uncapped telomeres can circumvent the need for otherwise-essential telomere capping proteins. The EMBO Journal (2010) 29, 4020-4034. doi:10.1038/emboj.2010.267; Published online 2 November 2010

Publication metadata

Author(s): Dewar JM, Lydall D

Publication type: Article

Publication status: Published

Journal: EMBO Journal

Year: 2010

Volume: 29

Issue: 23

Pages: 4020-4034

Print publication date: 02/11/2010

ISSN (print): 0261-4189

ISSN (electronic): 1460-2075

Publisher: Nature Publishing Group

URL: http://dx.doi.org/10.1038/emboj.2010.267

DOI: 10.1038/emboj.2010.267

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