In vivo repair of methylation damage in Aag 3-methyladenine DNA glycosylase null mouse cells

Smith, Stephen A.

doi:10.1093/nar/28.17.3294

Cited by 45 publications

(27 citation statements)

References 43 publications

(61 reference statements)

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“…In the absence of Aag, compensatory pathways (alternative DNA glycosylases or the nucleotide excision repair pathway) (27,34) did not effectively remove MMS-induced or MNNGinduced alkylation damage. Accumulated alkylation damage then slows progression of the replication fork in a checkpointindependent fashion (40).…”

Section: Discussionmentioning

confidence: 94%

“…2c). We next tested Aag (Ϫ/Ϫ) MEFs to directly evaluate the cytotoxicity of Aag substrates, since MMS causes a significant buildup of the principal Aag substrate 3-MeA in Aag (Ϫ/Ϫ) ES cells (33,34). Surprisingly, Aag substrates generated by MMS exposure conferred no increase in cytotoxicity (Fig.…”

Section: Aag Is Required To Initiate Ber Of Mms-and Mnng-induced Lesimentioning

confidence: 99%

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Base Excision Repair Intermediates Induce p53-independent Cytotoxic and Genotoxic Responses

Sobol

Kartalou

Almeida

et al. 2003

Journal of Biological Chemistry

169

158

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DNA alkylation damage is primarily repaired by the base excision repair (BER) machinery in mammalian cells. In repair of the N-alkylated purine base lesion, for example, alkyl adenine DNA glycosylase (Aag) recognizes and removes the base, and DNA polymerase ␤ (␤-pol) contributes the gap tailoring and DNA synthesis steps. It is the loss of ␤-pol-mediated 5 -deoxyribose phosphate removal that renders mouse fibroblasts alkylation-hypersensitive. Here we report that the hypersensitivity of ␤-pol-deficient cells after methyl methanesulfonate-induced alkylation damage is wholly dependent upon glycosylase-mediated initiation of repair, indicating that alkylated base lesions themselves are tolerated in these cells and demonstrate that ␤-pol protects against accumulation of toxic BER intermediates. Further, we find that these intermediates are initially tolerated in vivo by a second repair pathway, homologous recombination, inducing an increase in sister chromatid exchange events. If left unresolved, these BER intermediates trigger a rapid block in DNA synthesis and cytotoxicity. Surprisingly, both the cytotoxic and genotoxic signals are independent of both the p53 response and mismatch DNA repair pathways, demonstrating that p53 is not required for a functional BER pathway, that the observed damage response is not part of the p53 response network, and that the BER intermediate-induced cytotoxic and genotoxic effects are distinct from the mechanism engaged in response to mismatch repair signaling. These studies demonstrate that, although base damage is repaired by the BER pathway, incomplete BER intermediates are shuttled into the homologous recombination pathway, suggesting possible coordination between BER and the recombination machinery.

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Section: Discussionmentioning

confidence: 94%

Section: Aag Is Required To Initiate Ber Of Mms-and Mnng-induced Lesimentioning

confidence: 99%

Base Excision Repair Intermediates Induce p53-independent Cytotoxic and Genotoxic Responses

Sobol

Kartalou

Almeida

et al. 2003

Journal of Biological Chemistry

169

158

View full text Add to dashboard Cite

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“…However, all of the studies have been followed by discoveries of alternative DNA repair pathways for specific DNA lesions. For example, although ANPG (alkyl-Npurine DNA glycosylase) is the major DNA glycosylase for 3-methyladenine repair, 3-methyladenine disappears faster from the genome of Anpg Ϫ/Ϫ mice than would be expected from spontaneous depurination alone (47). Alternative repair of uracil residues in DNA is accomplished by the SMUG enzyme (18,41).…”

Section: Discussionmentioning

confidence: 99%

Proliferation Failure and Gamma Radiation Sensitivity of Fen1 Null Mutant Mice at the Blastocyst Stage

Larsen

Gran

Sæther

et al. 2003

Molecular and Cellular Biology

123

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Flap endonuclease 1 (FEN1) has been shown to remove 5 overhanging flap intermediates during base excision repair and to process the 5 ends of Okazaki fragments during lagging-strand DNA replication in vitro. To assess the in vivo role of the mammalian enzyme in repair and replication, we used a gene-targeting approach to generate mice lacking a functional Fen1 gene. Heterozygote animals appear normal, whereas complete depletion of FEN1 causes early embryonic lethality. Fen1 ؊/؊ blastocysts fail to form inner cell mass during cellular outgrowth, and a complete inactivation of DNA synthesis in giant cells of blastocyst outgrowth was observed. Exposure of Fen1 ؊/؊ blastocysts to gamma radiation caused extensive apoptosis, implying an essential role for FEN1 in the repair of radiation-induced DNA damage in vivo. Our data thus provide in vivo evidence for an essential function of FEN1 in DNA repair, as well as in DNA replication.Flap endonuclease 1 (FEN1) is a member of the RAD2 superfamily of nucleases, which play a critical role in DNA replication and repair in both prokaryotes and eukaryotes (16,17,24,26,55). The main function of FEN1 in replication is proposed to be the removal of displaced RNA-DNA primers synthesized by DNA polymerase ␣-primase during discontinuous lagging-strand replication. A similar single-stranded DNA flap structure is produced by excessive gap filling by a DNA repair polymerase during long-patch base excision repair (BER). Both biochemical and genetic studies support a role for FEN1 during these cellular processes. Similar 5Ј-flap intermediates are also formed in nonhomologous DNA end joining of double-strand DNA breaks and DNA recombination (25,57).The biochemistry of FEN1 has been studied extensively by several groups (reviewed in reference 32), and the crystal structures of two FEN1 orthologues from archaea have been solved (19,20). The enzyme employs a unique cleavage mechanism for substrates containing single-stranded 5Ј tails or 5Ј-flap structures. It recognizes the 5Ј end, tracking the length of the tail, and cleaves at the junction between double-stranded and single-stranded DNAs (40). Although FEN1 acts less efficiently as an exonuclease than as a flap endonuclease, it is likely that the enzyme employs similar mechanisms for both reactions (16,34).FEN1 has been shown to have an important role in the processing of intermediates formed during BER of modified structures in DNA. Recent evidence has indicated that in mammalian cells, BER is mediated through at least two subpathways with different repair patch sizes and different enzymes involved. These pathways have been designated singlenucleotide BER and long-patch BER (12,27,28). The choice of subpathways in BER depends on whether the 5Ј deoxyribose phosphate intermediate can be efficiently removed by the polymerase ␤ lyase activity to yield a 5Ј-phosphorylated DNA strand capable of serving as a substrate for DNA ligase (44). When such processing is inefficient, long-patch BER can occur, and FEN1 will remove the overhang formed by re...

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“…In Schizosaccharomyces pombe, NMPs may be repaired primarily through the NER pathway, rather than a BER pathway (36). In mammalian cells, a pathway may exist that repairs 7MeG in the absence of the ordinarily used Aag DNA glycosylase (37). However, deletion of the MAG1 gene in S. cerevisiae cells almost completely abolishes NMP repair (Fig.…”

Section: Discussionmentioning

confidence: 99%

Nucleosome Structure and Repair of N-Methylpurines in the GAL1-10 Genes of Saccharomyces cerevisiae

Smerdon

2002

Journal of Biological Chemistry

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Nucleosome structure and repair of N-methylpurines were analyzed at nucleotide resolution in the divergent GAL1-10 genes of intact yeast cells, encompassing their common upstream-activating sequence. In glucose cultures where genes are repressed, nucleosomes with fixed positions exist in regions adjacent to the upstream-activating sequence, and the variability of nucleosome positioning sharply increases with increasing distance from this sequence. Galactose induction causes nucleosome disruption throughout the region analyzed, with those nucleosomes close to the upstream-activating sequence being most striking. In glucose cultures, a strong correlation between N-methylpurine repair and nucleosome positioning was seen in nucleosomes with fixed positions, where slow and fast repair occurred in nucleosome core and linker DNA, respectively. Galactose induction enhanced N-methylpurine repair in both strands of nucleosome core DNA, being most dramatic in the clearly disrupted, fixed nucleosomes. Furthermore, N-methylpurines are repaired primarily by the Mag1-initiated base excision repair pathway, and nucleotide excision repair contributes little to repair of these lesions. Finally, N-methylpurine repair is significantly affected by nearest-neighbor nucleotides, where fast and slow repair occurred in sites between pyrimidines and purines, respectively. These results indicate that nucleosome positioning and DNA sequence significantly modulate Mag1-initiated base excision repair in intact yeast cells.

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In vivo repair of methylation damage in Aag 3-methyladenine DNA glycosylase null mouse cells

Cited by 45 publications

References 43 publications

Base Excision Repair Intermediates Induce p53-independent Cytotoxic and Genotoxic Responses

Base Excision Repair Intermediates Induce p53-independent Cytotoxic and Genotoxic Responses

Proliferation Failure and Gamma Radiation Sensitivity of Fen1 Null Mutant Mice at the Blastocyst Stage

Nucleosome Structure and Repair of N-Methylpurines in the GAL1-10 Genes of Saccharomyces cerevisiae

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