Abstract
Ultraviolet (UV) light induces DNA-damage checkpoints and mutagenesis, which are involved in cancer protection and tumorigenesis, respectively. How cells identify DNA lesions and convert them to checkpoint-activating structures is a major question. We show that during repair of UV lesions in noncycling cells, Exo1-mediated processing of nucleotide excision repair (NER) intermediates competes with repair DNA synthesis. Impediments of the refilling reaction allow Exo1 to generate extended ssDNA gaps, detectable by electron microscopy, which drive Mec1 kinase activation and will be refilled by long-patch repair synthesis, as shown by DNA combing. We provide evidence that this mechanism may be stimulated by closely opposing UV lesions, represents a strategy to redirect problematic repair intermediates to alternative repair pathways, and may also be extended to physically different DNA damages. Our work has significant implications for understanding the coordination between repair of DNA lesions and checkpoint pathways to preserve genome stability.
Copyright © 2010 Elsevier Inc. All rights reserved.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Cell Cycle* / genetics
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Cell Cycle* / radiation effects
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Chromosomes, Fungal* / radiation effects
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Chromosomes, Fungal* / ultrastructure
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DNA Damage*
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DNA Repair* / radiation effects
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DNA, Fungal / metabolism*
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DNA, Fungal / radiation effects
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DNA, Fungal / ultrastructure
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DNA, Single-Stranded / metabolism*
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DNA, Single-Stranded / ultrastructure
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Dose-Response Relationship, Radiation
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Enzyme Activation
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Exodeoxyribonucleases / genetics
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Exodeoxyribonucleases / metabolism*
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Gene Expression Regulation, Fungal
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Genomic Instability
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Intracellular Signaling Peptides and Proteins / metabolism
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Protein Serine-Threonine Kinases / metabolism
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Saccharomyces cerevisiae / enzymology*
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Saccharomyces cerevisiae / genetics
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Saccharomyces cerevisiae / growth & development
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Saccharomyces cerevisiae / radiation effects
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Saccharomyces cerevisiae Proteins / metabolism
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Time Factors
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Ultraviolet Rays
Substances
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DNA, Fungal
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DNA, Single-Stranded
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Intracellular Signaling Peptides and Proteins
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Saccharomyces cerevisiae Proteins
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MEC1 protein, S cerevisiae
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Protein Serine-Threonine Kinases
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Exodeoxyribonucleases
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exodeoxyribonuclease I