The Sequence Context‐Dependent Mispairing of 5‐Hydroxycytosine and 5‐Hydroxyuridine <i>in Vitro</i>

Purmal, Andrei A.; Lampman, Gary W.; Kow, Yoke W.; Wallace, Susan S.

doi:10.1111/j.1749-6632.1994.tb52852.x

Cited by 13 publications

(6 citation statements)

References 1 publication

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“…Interestingly, all of the mutations observed in the nei nth double mutant were C3T transitions ( Table 2). This is consistent with the ability of both enzymes to recognize oxidized cytosines (26), with the observed high frequency of C3T transitions in the spontaneous and oxidative mutational spectra (reviewed in reference 61), and with the ability of the major oxidized cytosine products to pair with A (29,44,48). Interestingly, although both enzymes recognize oxidized thymines equally well (26), no T events were recorded.…”

Section: Discussionsupporting

confidence: 85%

A Novel Role for Escherichia coli Endonuclease VIII in Prevention of Spontaneous G→T Transversions

1999

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In the bacterium Escherichia coli, oxidized pyrimidines are removed by two DNA glycosylases, endonuclease III and endonuclease VIII (endo VIII), encoded by the nth and neigenes, respectively. Double mutants lacking both of these activities exhibit a high spontaneous mutation frequency, and here we show that all of the mutations observed in the double mutants were G:C→A:T transitions; no thymine mutations were found. These findings are in agreement with the preponderance of C→T transitions in the oxidative and spontaneous mutational databases. The major oxidized purine lesion in DNA, 7,8-dihydro-8-oxoguanine (8-oxoG), is processed by two DNA glycosylases, formamidopyrimidine DNA glycosylase (Fpg), which removes 8-oxoG opposite C, and MutY DNA glycosylase, which removes misincorporated A opposite 8-oxoG. The high spontaneous mutation frequency previously observed in fpg mutY double mutants was significantly enhanced by the addition of the neimutation, suggesting an overlap in the substrate specificities between endo VIII and Fpg/MutY. When the mutational specificity was examined, all of the mutations observed were G:C→T:A transversions, indicating that in the absence of Fpg and MutY, endo VIII serves as a backup activity to remove 8-oxoG. This was confirmed by showing that, indeed, endo VIII can recognize 8-oxoG in vitro.

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Section: Discussionsupporting

confidence: 85%

A Novel Role for Escherichia coli Endonuclease VIII in Prevention of Spontaneous G→T Transversions

1999

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“…The mutagenic potential of hU was previously shown in vitro (56) and in vivo (38). Using a single-stranded vector, where hU cannot be removed by DNA n -glycosylases, Kreutzer and Essigmann reported an MF of 83% at this lesion (38).…”

Section: Discussionmentioning

confidence: 83%

Replication fork collapse is a major cause of the high mutation frequency at three-base lesion clusters

Sedletska¹,

Radicella²,

Sage³

2013

Nucleic Acids Research

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Unresolved repair of clustered DNA lesions can lead to the formation of deleterious double strand breaks (DSB) or to mutation induction. Here, we investigated the outcome of clusters composed of base lesions for which base excision repair enzymes have different kinetics of excision/incision. We designed multiply damaged sites (MDS) composed of a rapidly excised uracil (U) and two oxidized bases, 5-hydroxyuracil (hU) and 8-oxoguanine (oG), excised more slowly. Plasmids harboring these U-oG/hU MDS-carrying duplexes were introduced into Escherichia coli cells either wild type or deficient for DNA n-glycosylases. Induction of DSB was estimated from plasmid survival and mutagenesis determined by sequencing of surviving clones. We show that a large majority of MDS is converted to DSB, whereas almost all surviving clones are mutated at hU. We demonstrate that mutagenesis at hU is correlated with excision of the U placed on the opposite strand. We propose that excision of U by Ung initiates the loss of U-oG-carrying strand, resulting in enhanced mutagenesis at the lesion present on the opposite strand. Our results highlight the importance of the kinetics of excision by base excision repair DNA n-glycosylases in the processing and fate of MDS and provide evidence for the role of strand loss/replication fork collapse during the processing of MDS on their mutational consequences.

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“…Since replication resumes more rapidly when manganese is present, it is likely that replication would more frequently encounter lesions. Several polymerases have been shown to incorporate the wrong base on templates containing several common oxidized bases induced by H 2 O 2 , including 8-oxoguanine, thymine glycol, and 5-hydroxycytosine (90)(91)(92)(93)(94).…”

Section: Discussionmentioning

confidence: 99%

Manganese Is Required for the Rapid Recovery of DNA Synthesis following Oxidative Challenge in Escherichia coli

et al. 2019

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Divalent metals such as iron and manganese play an important role in the cellular response to oxidative challenges and are required as cofactors by many enzymes. However, how these metals affect replication after oxidative challenge is not known. Here, we show that replication in Escherichia coli is inhibited following a challenge with hydrogen peroxide and requires manganese for the rapid recovery of DNA synthesis. We show that the manganese-dependent recovery of DNA synthesis occurs independent of lesion repair, modestly improves cell survival, and is associated with elevated rates of mutagenesis. The Mn-dependent mutagenesis involves both replicative and translesion polymerases and requires prior disruption by H2O2 to occur. Taking these findings together, we propose that replication in E. coli is likely to utilize an iron-dependent enzyme(s) that becomes oxidized and inactivated during oxidative challenges. The data suggest that manganese remetallates these or alternative enzymes to allow genomic DNA replication to resume, although with reduced fidelity. IMPORTANCE Iron and manganese play important roles in how cell’s cope with oxygen stress. However, how these metals affect the ability of cells to replicate after oxidative challenges is not known. Here, we show that replication in Escherichia coli is inhibited following a challenge with hydrogen peroxide and requires manganese for the rapid recovery of DNA synthesis. The manganese-dependent recovery of DNA synthesis occurs independently of lesion repair and modestly improves survival, but it also increases the mutation rate in cells. The results imply that replication in E. coli is likely to utilize an iron-dependent enzyme(s) that becomes oxidized and inactivated during oxidative challenges. We propose that manganese remetallates these or alternative enzymes to allow genomic DNA replication to resume, although with reduced fidelity.

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The Sequence Context‐Dependent Mispairing of 5‐Hydroxycytosine and 5‐Hydroxyuridine in Vitro

Cited by 13 publications

References 1 publication

A Novel Role for Escherichia coli Endonuclease VIII in Prevention of Spontaneous G→T Transversions

A Novel Role for Escherichia coli Endonuclease VIII in Prevention of Spontaneous G→T Transversions

Replication fork collapse is a major cause of the high mutation frequency at three-base lesion clusters

Manganese Is Required for the Rapid Recovery of DNA Synthesis following Oxidative Challenge in Escherichia coli

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