Abstract
The uncapping of telomeres induces a DNA damage response. In Schizosaccharomyces pombe, deletion of pot1 + causes telomere uncapping and rapid telomere resection, resulting in chromosome fusion. Using the nmt-pot1-aid strain, we previously reported that Pot1 shut-off causes telomere loss and chromosome fusion in S. pombe. However, the factors responsible for the resection of uncapped telomeres remain unknown. In this study, we investigated these factors and found that concomitant deletion of rqh1 + and exo1 + alleviated the loss of telomeres following Pot1 shut-off, suggesting that Rqh1 and Exo1 are redundantly involved in the resection of uncapped telomeres. We also investigated the role of Rqh1 helicase activity and found it to be essential for the resection of uncapped telomeres. Moreover, we found that Dna2 and Exo1 function redundantly in the resection of uncapped telomeres. Taken together, these results suggest that Exo1 and Rqh1-Dna2 redundantly contribute to the resection of uncapped telomeres. Therefore, our results demonstrate that nmt-pot1-aid is an important model strain to study the role of helicases and nucleases in the resection of uncapped telomeres and to improve our understanding of DNA double-strand break repair.
Highlights
Telomeres are protected by telomere-capping proteins [1]
We showed that deletion of rqh1+ does not affect telomere loss in the nmt-pot1-aid strain of S. pombe following protein 1 (Pot1) shut-off in the presence of thiamine and auxin [15]
This finding suggests that either Rqh1 is not involved in telomere resection or Rqh1 is involved in resection but another redundant pathway–possibly mediated by Exo1–can resect uncapped telomeres, in the absence of Rqh1
Summary
Telomeres are protected by telomere-capping proteins [1]. As a consequence of critically short telomere or dysfunction of telomere-capping proteins, telomeres become uncapped and are recognized as double-strand breaks (DSB) [2,3,4]. In Saccharomyces cerevisiae, a 5 ́ to 3 ́ exonuclease, Exo, and a RecQ helicase, Sgs, are redundantly involved in DSB resection [5]. Exo and the RecQ helicase, Rqh, mediate DSB resection pathways in Schizosaccharomyces pombe [6, 7]. In S. cerevisiae, inactivation of the telomere-capping protein Cdc by the temperature sensitive cdc allele results in telomere uncapping [8]. Resection of cdc13-1induced uncapped telomeres involves both Exo and Sgs activity, Exo plays more
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