Abstract
The replication checkpoint is a dedicated sensor-response system activated by impeded replication forks. It stabilizes stalled forks and arrests division, thereby preserving genome integrity and promoting cell survival. In budding yeast, Tof1 is thought to act as a specific mediator of the replication checkpoint signal that activates the effector kinase Rad53. Here we report studies of fission yeast Swi1, a Tof1-related protein required for a programmed fork-pausing event necessary for mating type switching. Our studies have shown that Swi1 is vital for proficient activation of the Rad53-like checkpoint kinase Cds1. Together they are required to prevent fork collapse in the ribosomal DNA repeats, and they also prevent irreversible fork arrest at a newly identified hydroxyurea pause site. Swi1 also has Cds1-independent functions. Rad22 DNA repair foci form during S phase in swi1 mutants and to a lesser extent in cds1 mutants, indicative of fork collapse. Mus81, a DNA endonuclease required for recovery from collapsed forks, is vital in swi1 but not cds1 mutants. Swi1 is recruited to chromatin during S phase. We propose that Swi1 stabilizes replication forks in a configuration that is recognized by replication checkpoint sensors.
Publication types
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Research Support, Non-U.S. Gov't
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Animals
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Cell Cycle / physiology
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Cell Cycle Proteins
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Cell Nucleus / metabolism
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Checkpoint Kinase 2
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DNA Replication*
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DNA, Fungal / genetics
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DNA, Fungal / metabolism
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DNA, Fungal / radiation effects
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DNA-Binding Proteins / genetics
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DNA-Binding Proteins / metabolism
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Endonucleases*
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Protein Kinases / genetics
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Protein Kinases / metabolism*
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Protein Serine-Threonine Kinases*
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Recombinant Fusion Proteins / genetics
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Recombinant Fusion Proteins / metabolism
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Saccharomyces cerevisiae Proteins
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Schizosaccharomyces / cytology
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Schizosaccharomyces / genetics*
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Schizosaccharomyces / metabolism
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Schizosaccharomyces / radiation effects
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Schizosaccharomyces pombe Proteins / genetics
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Schizosaccharomyces pombe Proteins / metabolism
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Transcription Factors / genetics
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Transcription Factors / metabolism*
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Ultraviolet Rays
Substances
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Cell Cycle Proteins
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DNA, Fungal
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DNA-Binding Proteins
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Recombinant Fusion Proteins
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Saccharomyces cerevisiae Proteins
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Schizosaccharomyces pombe Proteins
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Transcription Factors
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rad52 protein, S pombe
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swi1 protein, S pombe
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Protein Kinases
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Checkpoint Kinase 2
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Cds1 protein, S pombe
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Protein Serine-Threonine Kinases
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Endonucleases
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MUS81 protein, S cerevisiae