Closely opposed apurinic/apyrimidinic sites are converted to double strand breaks in Escherichia coli even in the absence of exonuclease III, endonuclease IV, nucleotide excision repair and AP lyase cleavage

Harrison, Louis; Brame, Katherine L.; Geltz, Laura E.

doi:10.1016/j.dnarep.2005.10.009

Cited by 50 publications

(48 citation statements)

References 44 publications

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“…It is interesting to note that, although it would have been especially informative to have conducted TM studies with AP THF in a strain that is deficient in xth nfo nfi and uvrA concurrently, thus compromising all known AP site repair pathways simultaneously, we were unable to construct such a quadruple mutant strain, even when using a P1 stock that produced viable mutants in other backgrounds (Table S1). Together, these results support recent observations that repair of AP sites can occur through another, unknown mechanism in addition to those mediated by AP endonucleases, AP lyases, NER, or Nfi (25). Similarly, the strand breaks are processed in the absence of AP endonucleases, Nfi, and NER.…”

Section: Discussionsupporting

confidence: 78%

Abasic sites and strand breaks in DNA cause transcriptional mutagenesis in Escherichia coli

Clauson

Oestreich

Austin

et al. 2010

Proc. Natl. Acad. Sci. U.S.A.

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DNA damage occurs continuously, and faithful replication and transcription are essential for maintaining cell viability. Cells in nature are not dividing and replicating DNA often; therefore it is important to consider the outcome of RNA polymerase (RNAP) encounters with DNA damage. Base damage in the DNA can affect transcriptional fidelity, leading to production of mutant mRNA and protein in a process termed transcriptional mutagenesis (TM). Abasic (AP) sites and strand breaks are frequently occurring, spontaneous damages that are also base excision repair (BER) intermediates. In vitro studies have demonstrated that these lesions can be bypassed by RNAP; however this has never been assessed in vivo. This study demonstrates that RNAP is capable of bypassing AP sites and strand breaks in Escherichia coli and results in TM through adenine incorporation in nascent mRNA. Elimination of the enzymes that process these lesions further increases TM; however, such mutants can still complete repair by other downstream pathways. These results show that AP sites and strand breaks can result in mutagenic RNAP bypass and have important implications for the biologic endpoints of DNA damage.ost cells in nature are in a state of limited growth and are therefore not often engaged in replication (1, 2). Thus, the functional viability of most types of cells likely depends more on faithful transcription and translation than on faithful replication. Several base damages are bypassed in vivo by RNA polymerase (RNAP) in a mutagenic manner, resulting in transcriptional mutagenesis (TM) (3-7). In nondividing cell populations, TM could have a large contribution to the mutant protein burden and resulting cellular phenotype, compared with replicationbased mutagenesis events.Base excision repair (BER) is responsible for the processing of many small lesions, and in particular, those that do not cause significant helix distortion. During BER these lesions are removed by specialized DNA N-glycosylases. Monofunctional glycosylases remove the damaged base, leaving an abasic (AP) site. Bifunctional glycosylase/AP lyase enzymes remove the lesion and nick the DNA strand via β-or β,δ-elimination, resulting in a 3′ blocking group (8). Next, AP endonucleases process the AP sites and 3′ blocking groups to produce 3′-termini compatible with subsequent DNA repair synthesis (8, 9). In vitro, RNAP can bypass several types of repair intermediates, including AP sites and various strand breaks (10-14). Whether RNAP is capable of bypassing abasic sites and strand breaks in live organisms is an important issue for defining the spectrum of DNA damages that can cause TM, as well as for understanding the relationships between RNAP and DNA repair processes. Here we have demonstrated that RNAP is capable of bypassing AP sites and strand breaks in Escherichia coli. ResultsWe investigated TM mediated by AP sites and strand breaks by using damage-tailored plasmid constructs and using a transcriptional mutagenesis luciferase assay system (TM-LAS) (3, 15) (Fig. S1) in iso...

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Section: Discussionsupporting

confidence: 78%

Abasic sites and strand breaks in DNA cause transcriptional mutagenesis in Escherichia coli

Clauson

Oestreich

Austin

et al. 2010

Proc. Natl. Acad. Sci. U.S.A.

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“…In general, opposing lesions were converted to SSBs if they were positioned ≥ 3 bps apart. Work in bacteria and mammalian cells has shown similar results with respect to AP sites or the furan abasic site analog, and has demonstrated that opposing lesions can be converted to DSBs in cells (15; 23). Interestingly, studies examining closely opposed base damage in bacteria have shown that the lesions are not converted to DSBs, but rather enhance mutation frequency at the individual lesions in the cluster (24–27).…”

Section: Introductionmentioning

confidence: 82%

Apex1 can cleave complex clustered DNA lesions in cells

2009

Self Cite

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Current data indicate that clustered DNA damage generated by ionizing radiation contains 2-5 damages within 20 bps. The complexity of clustered damage is also believed to increase as the linear energy transfer of the radiation increases. Complex lesions are therefore biologically relevant especially with the use of carbon ion beam therapy to treat cancer. Since two closely opposed AP site analogs (furans) are converted to a double strand break (DSB) in cells, we hypothesized that breakage could be compromised by increasing the complexity of the cluster. We have examined the repair of clusters containing three and four lesions in mouse fibroblasts using a luciferase reporter plasmid. The addition of a third furan did reduce but not eliminate cleavage, while a tandem 8-oxo-7,8 dihydroguanine (8oxoG) immediately 5' to one furan in a two or three furan cluster decreased DSB formation by a small amount. In vitro studies using nuclear extracts demonstrated that the tandem 8oxoG was not removed under conditions where the furan was cleaved, but the presence of the 8oxoG reduced cleavage at the furan. Interestingly, a cluster of an 8oxoG opposite a furan did not form a DSB in cells. We have shown that Apex1 can cleave these complex clustered lesions in cells. This therefore indicates that Apex1 can generate complex DSBs from clustered lesions consisting of base damage and AP sites. Repair of these complex DSBs may be compromised by the nearby oxidative damage resulting in potentially lethal and biologically relevant damage.

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“…As a consequence, nucleotides can be oxidized (such as guanine to 8-oxoG) resulting in base transversion (GC-TA), abasic sites and DNA single-and double-strand breaks. (7)(8)(9)(10)(11)(12) For cellular integrity, DNA double-strand breaks (DSB) can be fatal and their repair is initiated by the cellular DNA damage response (DDR) consisting of a multi-protein signalling cascade. (13,14) An early event in DSB response is phosphorylation of the H2A subtype histone H2AX at ser-139 (also known as γH2AX) by the phosphatidylinositol 3-like kinases ATM, ATR and DNA-PK.…”

Section: Introductionmentioning

confidence: 99%

Overt Increase of Oxidative Stress and DNA Damage in Murine and Human Colitis and Colitis-Associated Neoplasia

Frick

Khare

Paul

et al. 2018

Molecular Cancer Research

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Patients with inflammatory bowel disease (IBD) have a higher risk of developing colitis-associated-cancer (CAC), however, the underlying processes of disease progression are not completely understood. Here, the molecular processes of inflammation-driven colon carcinogenesis were investigated using IL-10 deficient mice (IL-10 KO). IL-10 KO mice were euthanized after development of colitis and dysplasia. Immunohistochemistry Enhanced DSBs in IL-10 KO organoids were confirmed by comet-assay and increased expression of γH2AX. Human clinical specimens exhibited significantly higher γH2AX and 8-oxoG in IBD, dysplasia and CAC compared to normal mucosa.These data indicate that inflammation-driven colon carcinogenesis in IL-10 KO mice and IBD patients is associated with oxidative DNA damage and overt presence of DSB.on May 9, 2018.

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Closely opposed apurinic/apyrimidinic sites are converted to double strand breaks in Escherichia coli even in the absence of exonuclease III, endonuclease IV, nucleotide excision repair and AP lyase cleavage

Cited by 50 publications

References 44 publications

Abasic sites and strand breaks in DNA cause transcriptional mutagenesis in Escherichia coli

Abasic sites and strand breaks in DNA cause transcriptional mutagenesis in Escherichia coli

Apex1 can cleave complex clustered DNA lesions in cells

Overt Increase of Oxidative Stress and DNA Damage in Murine and Human Colitis and Colitis-Associated Neoplasia

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