Accumulation of true single strand breaks and AP sites in base excision repair deficient cells

AbstractPARP1 regulates the repair of DNA single strand breaks (SSBs) generated directly, or during base excision repair (BER). However, the role of PARP2 in these and other repair mechanisms is unknown. Here, we report a requirement for PARP2 in stabilising replication forks that encounter BER intermediates through Fbh1-dependent regulation of Rad51. Whilst PARP2 is dispensable for tolerance of cells to SSBs or homologous recombination dysfunction, it is redundant with PARP1 in BER. Therefore, combined disruption of PARP1 and PARP2 leads to defective BER, resulting in elevated levels of replication associated DNA damage due to an inability to stabilise Rad51 at damaged replication forks and prevent uncontrolled DNA resection. Together, our results demonstrate how PARP1 and PARP2 regulate two independent, but intrinsically linked aspects of DNA base damage tolerance by promoting BER directly, and through stabilising replication forks that encounter BER intermediates.

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The Transition of Closely Opposed Lesions to Double-Strand Breaks during Long-Patch Base Excision Repair Is Prevented by the Coordinated Action of DNA Polymerase δ and Rad27/Fen1

Molecular and Cellular Biology ◽

10.1128/mcb.01499-08 ◽

2008 ◽

Vol 29 (5) ◽

pp. 1212-1221 ◽

Cited By ~ 33

Author(s):

Wenjian Ma ◽

Vijayalakshmi Panduri ◽

Joan F. Sterling ◽

Bennett Van Houten ◽

Dmitry A. Gordenin ◽

...

Keyword(s):

Dna Polymerase ◽

Base Excision Repair ◽

Excision Repair ◽

Double Strand Breaks ◽

Single Strand ◽

S1 Nuclease ◽

Single Strand Break ◽

Strand Breaks ◽

Dna Polymerase Δ ◽

Base Excision

ABSTRACT DNA double-strand breaks can result from closely opposed breaks induced directly in complementary strands. Alternatively, double-strand breaks could be generated during repair of clustered damage, where the repair of closely opposed lesions has to be well coordinated. Using single and multiple mutants of Saccharomyces cerevisiae (budding yeast) that impede the interaction of DNA polymerase δ and the 5′-flap endonuclease Rad27/Fen1 with the PCNA sliding clamp, we show that the lack of coordination between these components during long-patch base excision repair of alkylation damage can result in many double-strand breaks within the chromosomes of nondividing haploid cells. This contrasts with the efficient repair of nonclustered methyl methanesulfonate-induced lesions, as measured by quantitative PCR and S1 nuclease cleavage of single-strand break sites. We conclude that closely opposed single-strand lesions are a unique threat to the genome and that repair of closely opposed strand damage requires greater spatial and temporal coordination between the participating proteins than does widely spaced damage in order to prevent the development of double-strand breaks.

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Base excision repair and its implications to cancer therapy

Essays in Biochemistry ◽

10.1042/ebc20200013 ◽

2020 ◽

Vol 64 (5) ◽

pp. 831-843 ◽

Cited By ~ 1

Author(s):

Gabrielle J. Grundy ◽

Jason L. Parsons

Keyword(s):

Oxidative Stress ◽

Cancer Cells ◽

Base Excision Repair ◽

Excision Repair ◽

Repair Process ◽

Loss Of Function ◽

Strand Breaks ◽

Single Strand Breaks ◽

Base Excision ◽

Integrity Of Dna

Abstract Base excision repair (BER) has evolved to preserve the integrity of DNA following cellular oxidative stress and in response to exogenous insults. The pathway is a coordinated, sequential process involving 30 proteins or more in which single strand breaks are generated as intermediates during the repair process. While deficiencies in BER activity can lead to high mutation rates and tumorigenesis, cancer cells often rely on increased BER activity to tolerate oxidative stress. Targeting BER has been an attractive strategy to overwhelm cancer cells with DNA damage, improve the efficacy of radiotherapy and/or chemotherapy, or form part of a lethal combination with a cancer specific mutation/loss of function. We provide an update on the progress of inhibitors to enzymes involved in BER, and some of the challenges faced with targeting the BER pathway.

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DNA breaks and chromosomal aberrations arise when replication meets base excision repair

The Journal of Cell Biology ◽

10.1083/jcb.201312078 ◽

2014 ◽

Vol 206 (1) ◽

pp. 29-43 ◽

Cited By ~ 65

Author(s):

Michael Ensminger ◽

Lucie Iloff ◽

Christian Ebel ◽

Teodora Nikolova ◽

Bernd Kaina ◽

...

Keyword(s):

Base Excision Repair ◽

Chromosomal Aberrations ◽

Excision Repair ◽

Double Strand Breaks ◽

Replication Forks ◽

Dna Double Strand Breaks ◽

Dna Breaks ◽

Strand Breaks ◽

Single Strand Breaks ◽

Base Excision

Exposures that methylate DNA potently induce DNA double-strand breaks (DSBs) and chromosomal aberrations, which are thought to arise when damaged bases block DNA replication. Here, we demonstrate that DNA methylation damage causes DSB formation when replication interferes with base excision repair (BER), the predominant pathway for repairing methylated bases. We show that cells defective in the N-methylpurine DNA glycosylase, which fail to remove N-methylpurines from DNA and do not initiate BER, display strongly reduced levels of methylation-induced DSBs and chromosomal aberrations compared with wild-type cells. Also, cells unable to generate single-strand breaks (SSBs) at apurinic/apyrimidinic sites do not form DSBs immediately after methylation damage. In contrast, cells deficient in x-ray cross-complementing protein 1, DNA polymerase β, or poly (ADP-ribose) polymerase 1 activity, all of which fail to seal SSBs induced at apurinic/apyrimidinic sites, exhibit strongly elevated levels of methylation-induced DSBs and chromosomal aberrations. We propose that DSBs and chromosomal aberrations after treatment with N-alkylators arise when replication forks collide with SSBs generated during BER.

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Bacterial DNA repair genes and their eukaryotic homologues: 1. Mutations in genes involved in base excision repair (BER) and DNA-end processors and their implication in mutagenesis and human disease.

Acta Biochimica Polonica ◽

10.18388/abp.2007_3219 ◽

2007 ◽

Vol 54 (3) ◽

pp. 413-434 ◽

Cited By ~ 35

Author(s):

Joanna Krwawicz ◽

Katarzyna D Arczewska ◽

Elzbieta Speina ◽

Agnieszka Maciejewska ◽

Elzbieta Grzesiuk

Keyword(s):

Base Excision Repair ◽

Excision Repair ◽

Dna Bases ◽

Cancer Therapies ◽

Strand Breaks ◽

Single Strand Breaks ◽

Modified Dna ◽

Environmental Agents ◽

Base Excision ◽

Bacterial Mutagenesis

Base excision repair (BER) pathway executed by a complex network of proteins is the major system responsible for the removal of damaged DNA bases and repair of DNA single strand breaks (SSBs) generated by environmental agents, such as certain cancer therapies, or arising spontaneously during cellular metabolism. Both modified DNA bases and SSBs with ends other than 3'-OH and 5'-P are repaired either by replacement of a single or of more nucleotides in the processes called short-patch BER (SP-BER) or long-patch BER (LP-BER), respectively. In contrast to Escherichia coli cells, in human ones, the two BER sub-pathways are operated by different sets of proteins. In this review the selection between SP- and LP-BER and mutations in BER and end-processors genes and their contribution to bacterial mutagenesis and human diseases are considered.

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DNA DAMAGE AND REPAIR IN EUKARYOTIC CELLS

Genetics ◽

10.1093/genetics/78.1.139 ◽

1974 ◽

Vol 78 (1) ◽

pp. 139-148

Author(s):

R B Painter

Keyword(s):

Ionizing Radiation ◽

Excision Repair ◽

Double Strand Breaks ◽

Single Strand ◽

Premature Aging ◽

Cross Linking ◽

Base Damage ◽

Strand Breaks ◽

Single Strand Breaks ◽

Post Replication Repair

ABSTRACT Damage in DNA after irradiation can be classified into five kinds: base damage, single-strand breaks, double-strand breaks, DNA-DNA cross-linking, and DNA-protein cross-linking. Of these, repair of base damage is the best understood. In eukaryotes, at least three repair systems are known that can deal with base damage: photoreactivation, excision repair, and post-replication repair. Photoreactivation is specific for UV-induced damage and occurs widely throughout the biosphere, although it seems to be absent from placental mammals. Excision repair is present in prokaryotes and in animals but does not seem to be present in plants. Post-replication repair is poorly understood. Recent reports indicate that growing points in mammalian DNA simply skip past UV-induced lesions, leaving gaps in newly made DNA that are subsequently filled in by de novo synthesis. Evidence that this concept is oversimplified or incorrect is presented.—Single-strand breaks are induced by ionizing radiation but most cells can rapidly repair most or all of them, even after supralethal doses. The chemistry of the fragments formed when breaks are induced by ionizing radiation is complex and poorly understood. Therefore, the intermediate steps in the repair of single-strand breaks are unknown. Double-strand breaks and the two kinds of cross-linking have been studied very little and almost nothing is known about their mechanisms for repair.—The role of mammalian DNA repair in mutations is not known. Although there is evidence that defective repair can lead to cancer and/or premature aging in humans, the relationship between the molecular defects and the diseased state remains obscure.

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