Factors affecting template switch recombination associated with restarted DNA replication
- University of Oxford, United Kingdom
Abstract
Homologous recombination helps ensure the timely completion of genome duplication by restarting collapsed replication forks. This beneficial function is not without risk however, as replication restarted by homologous recombination is prone to template switching (TS) that can generate deleterious genome rearrangements associated with diseases such as cancer. In a previous paper (Nguyen et al., 2015), we established an assay for studying TS in Schizosaccharomyces pombe. Here, we advance this work by showing that TS is detected up to 75 kb downstream of a collapsed replication fork and can be triggered by head-on collision between the restarted fork and RNA Polymerase III transcription. The Pif1 DNA helicase, Pfh1, promotes efficient restart and also suppresses TS. A further three conserved helicases (Fbh1, Rqh1 and Srs2) strongly suppress TS, but there is no change in TS frequency in cells lacking Fml1 or Mus81. We discuss how these factors likely influence TS.
Data availability
All data generated or analysed during this study are included in the manuscript and supporting files.
Article and author information
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Funding
Wellcome (090767/Z/09/Z)
- Matthew C Whitby
Medical Research Council (MR/P028292/1)
- Matthew C Whitby
Biotechnology and Biological Sciences Research Council (BB/P019706/1)
- Matthew C Whitby
The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.
Copyright
© 2019, Jalan et al.
This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.
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Factors affecting template switch recombination associated with restarted DNA replication
eLife 8:e41697.
https://doi.org/10.7554/eLife.41697
Further reading
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- Chromosomes and Gene Expression
The association between late replication timing and low transcription rates in eukaryotic heterochromatin is well known, yet the specific mechanisms underlying this link remain uncertain. In Saccharomyces cerevisiae, the histone deacetylase Sir2 is required for both transcriptional silencing and late replication at the repetitive ribosomal DNA (rDNA) arrays. We have previously reported that in the absence of SIR2, a de-repressed RNA PolII repositions MCM replicative helicases from their loading site at the ribosomal origin, where they abut well-positioned, high-occupancy nucleosomes, to an adjacent region with lower nucleosome occupancy. By developing a method that can distinguish activation of closely spaced MCM complexes, here we show that the displaced MCMs at rDNA origins have increased firing propensity compared to the nondisplaced MCMs. Furthermore, we found that both activation of the repositioned MCMs and low occupancy of the adjacent nucleosomes critically depend on the chromatin remodeling activity of FUN30. Our study elucidates the mechanism by which Sir2 delays replication timing, and it demonstrates, for the first time, that activation of a specific replication origin in vivo relies on the nucleosome context shaped by a single chromatin remodeler.
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