The checkpoint response to replication stress. DNA Repair (Amst) 8:1038-1046

FIRC Institute of Molecular Oncology Foundation (IFOM-IEO campus), Via Adamello 16, 20139 Milan, Italy.
DNA repair (Impact Factor: 3.11). 06/2009; 8(9):1038-46. DOI: 10.1016/j.dnarep.2009.04.014
Source: PubMed


Genome instability is a hallmark of cancer cells, and defective DNA replication, repair and recombination have been linked to its etiology. Increasing evidence suggests that proteins influencing S-phase processes such as replication fork movement and stability, repair events and replication completion, have significant roles in maintaining genome stability. DNA damage and replication stress activate a signal transduction cascade, often referred to as the checkpoint response. A central goal of the replication checkpoint is to maintain the integrity of the replication forks while facilitating replication completion and DNA repair and coordinating these events with cell cycle transitions. Progression through the cell cycle in spite of defective or incomplete DNA synthesis or unrepaired DNA lesions may result in broken chromosomes, genome aberrations, and an accumulation of mutations. In this review we discuss the multiple roles of the replication checkpoint during replication and in response to replication stress, as well as the enzymatic activities that cooperate with the checkpoint pathway to promote fork resumption and repair of DNA lesions thereby contributing to genome integrity.

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Available from: Dana Branzei, Oct 11, 2015
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    • "Upon replication stress, cells trigger a mechanism called the S-phase checkpoint to allow for proper completion of replication before exit out of S phase. Because this pathway is essential for genomic stability, as evidenced by the development of cancer or cell death in checkpoint mutants (Zeman and Cimprich 2014) and strict conservation in eukaryotic cells, mechanisms of S-phase checkpoint activation have been studied extensively (Branzei and Foiani 2009). When replication forks stall in budding yeast cells, excess single-stranded DNA (ssDNA) is produced that is bound by replication protein A (RPA). "
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    ABSTRACT: When cells undergo replication stress, proper checkpoint activation and deactivation are critical for genomic stability and cell survival, and therefore must be highly regulated. Although mechanisms of checkpoint activation are well studied, mechanisms of checkpoint deactivation are far less understood. Previously, we reported that chromatin remodeling factors Isw2 and Ino80 attenuate the S phase checkpoint activity, especially during recovery from hydroxyurea in Saccharomyces cerevisiae. In this study, we found that Isw2 and Ino80 have a more pronounced role in attenuating checkpoint activity during late S phase in the presence of methyl methanesulfonate (MMS). We therefore screened for checkpoint factors required for Isw2 and Ino80 checkpoint attenuation in the presence of MMS. Here we demonstrate that Isw2 and Ino80 antagonize checkpoint activators and attenuate checkpoint activity in S phase in MMS either through a currently unknown pathway or through RPA. Unexpectedly, we found that Isw2 and Ino80 increase chromatin accessibility around replicating regions in the presence of MMS, through a novel mechanism. Furthermore, through growth assays, we provide additional evidence that Isw2 and Ino80 partially counteract checkpoint activators specifically in the presence of MMS. Based on these results, we propose that Isw2 and Ino80 attenuate S phase checkpoint activity through a novel mechanism. Copyright © 2015, The Genetics Society of America.
    Full-text · Article · Feb 2015 · Genetics
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    • "Cds1p can maintain the stability of stalled replication forks by regulating Mus81p-Eme1p nuclease, Rqh1p, a RecQ-family helicase involved in suppressing inappropriate recombination during replication, and Rad60, a protein required for recombinational repair during replication. This interaction reveals a direct link between Cds1p kinase and recombinational repair processes (Kai and Wang, 2003; Branzei and Foiani, 2009). Thus in the future it should be tested whether Rgf1p might play some role in processing blocked replication forks to prevent subsequent recombinogenic processes or whether Rgf1p's function in cytoskeleton dynamics might indirectly feed into these Rad52p-dependent processes. "
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    ABSTRACT: Guanine nucleotide exchange factors (GEFs) control many aspects of cell morphogenesis by turning on Rho-GTPases. The fission yeast exchange factor Rgf1p (Rho gef1) specifically regulates Rho1p during polarized growth and localizes to cortical sites. Here we report that Rgf1p is re-localized to the cell nucleus during the stalled replication caused by hydroxyurea (HU). Import to the nucleus is mediated by a nuclear localization sequence (NLS) at the N-terminus of Rgf1p, while release into the cytoplasm requires two leucine-rich nuclear export sequences (NES) at the C-terminus. Moreover, Rgf1p nuclear accumulation during replication arrest depends on the 14-3-3 chaperone Rad24p and on the DNA replication checkpoint kinase Cds1p. Both proteins control the nuclear accumulation of Rgf1p by inhibition of its nuclear export. A mutant, Rgf1p-9A, that substitutes 9 Ser potential phosphorylation Cds1p sites for Ala fails to accumulate in the nucleus in response to replication stress and this correlates with a severe defect in survival in the presence of HU. In conclusion, we propose that the regulation of Rgf1p could be part of the mechanism by which Cds1p and Rad24p promote survival in the presence of chronic replication stress. It will be of general interest to understand whether the same is true for homologs of Rgf1p in budding yeast and higher eukaryotes.
    Full-text · Article · Jan 2014 · Molecular biology of the cell
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    • "Stalled replication forks must be restarted in order to complete replication. Checkpoint related kinases, such as Mec1 and Rad53 (Chk2 ortholog) in yeast, play important roles in regulating restart by activating appropriate pathways to resolve fork blockage (63,64). One important step in this process is to reduce the frequency of HR that could lead to destabilization of replication forks and generate toxic HR intermediates (63,64). "
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    ABSTRACT: Replication Protein A (RPA) is a heterotrimeric protein complex that binds single-stranded DNA. In plants, multiple genes encode the three RPA subunits (RPA1, RPA2 and RPA3), including five RPA1-like genes in Arabidopsis. Phylogenetic analysis suggests two distinct groups composed of RPA1A, RPA1C, RPA1E (ACE group) and RPA1B, RPA1D (BD group). ACE-group members are transcriptionally induced by ionizing radiation, while BD-group members show higher basal transcription and are not induced by ionizing radiation. Analysis of rpa1 T-DNA insertion mutants demonstrates that although each mutant line is likely null, all mutant lines are viable and display normal vegetative growth. The rpa1c and rpa1e single mutants however display hypersensitivity to ionizing radiation, and combination of rpa1c and rpa1e results in additive hypersensitivity to a variety of DNA damaging agents. Combination of the partially sterile rpa1a with rpa1c results in complete sterility, incomplete synapsis and meiotic chromosome fragmentation, suggesting an early role for RPA1C in promoting homologous recombination. Combination of either rpa1c and/or rpa1e with atr revealed additive hypersensitivity phenotypes consistent with each functioning in unique repair pathways. In contrast, rpa1b rpa1d double mutant plants display slow growth and developmental defects under non-damaging conditions. We show these defects in the rpa1b rpa1d mutant are likely the result of defective DNA replication leading to reduction in cell division.
    Full-text · Article · Dec 2013 · Nucleic Acids Research
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