Mismatch repair-dependent processing of methylation damage gives rise to persistent single-stranded gaps in newly replicated DNA

Mojas, Nina; Lopes, Massimo; Jiricny, Josef

doi:10.1101/gad.455407

Cited by 159 publications

(174 citation statements)

References 42 publications

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“…The frequency of DSBs was quantitatively correlated with the frequency of apoptosis. This supports a model where MMR generates gaps in the DNA (Mojas et al, 2007) that block replication, which leads to DSBs at collapsed replication forks in the second cell cycle after treatment (Ochs and Kaina, 2000; for review see Kaina et al, 2007). Thus, DSBs are postulated to act as a downstream trigger of O 6 MeG-induced apoptosis.…”

Section: Discussionsupporting

confidence: 68%

Temozolomide- and fotemustine-induced apoptosis in human malignant melanoma cells: response related to MGMT, MMR, DSBs, and p53

Naumann¹,

Roos²,

Jöst³

et al. 2009

Br J Cancer

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Malignant melanomas are highly resistant to chemotherapy. First-line chemotherapeutics used in melanoma therapy are the methylating agents dacarbazine (DTIC) and temozolomide (TMZ) and the chloroethylating agents BCNU and fotemustine. Here, we determined the mode of cell death in 11 melanoma cell lines upon exposure to TMZ and fotemustine. We show for the first time that TMZ induces apoptosis in melanoma cells, using therapeutic doses. For both TMZ and fotemustine apoptosis is the dominant mode of cell death. The contribution of necrosis to total cell death varied between 10 and 40%. The O 6 -methylguanine-DNA methyltransferase (MGMT) activity in the cell lines was between 0 and 1100 fmol mg À1 protein, and there was a correlation between MGMT activity and the level of resistance to TMZ and fotemustine. MGMT inactivation by O 6 -benzylguanine sensitized all melanoma cell lines expressing MGMT to TMZ and fotemustine-induced apoptosis, and MGMT transfection attenuated the apoptotic response. This supports that O 6 -alkylguanines are critical lesions involved in the initiation of programmed melanoma cell death. One of the cell lines (MZ7), derived from a patient subjected to DTIC therapy, exhibited a high level of resistance to TMZ without expressing MGMT. This was related to an impaired expression of MSH2 and MSH6. The cells were not cross-resistant to fotemustine. Although these data indicate that methylating drug resistance of melanoma cells can be acquired by down-regulation of mismatch repair, a correlation between MSH2 and MSH6 expression in the different lines and TMZ sensitivity was not found. Apoptosis in melanoma cells induced by TMZ and fotemustine was accompanied by double-strand break (DSB) formation (as determined by H2AX phosphorylation) and caspase-3 and -7 activation as well as PARP cleavage. For TMZ, DSBs correlated significantly with the apoptotic response, whereas for fotemustine a correlation was not found. Melanoma lines expressing p53 wild-type were more resistant to TMZ and fotemustine than p53 mutant melanoma lines, which is in marked contrast to previous data reported for glioma cells treated with TMZ. Overall, the findings are in line with the model that in melanoma cells TMZ-induced O 6 -methylguanine triggers the apoptotic (and necrotic) pathway through DSBs, whereas for chloroethylating agents apoptosis is triggered in a more complex manner.

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Section: Discussionsupporting

confidence: 68%

Temozolomide- and fotemustine-induced apoptosis in human malignant melanoma cells: response related to MGMT, MMR, DSBs, and p53

Naumann¹,

Roos²,

Jöst³

et al. 2009

Br J Cancer

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“…In this scheme, homologous recombination performs a vital rescue function. The Jiricny lab has recently reported that treatment of mammalian cells with MNNG gives rise to MMR-dependent single-stranded gaps in newly replicated DNA (Mojas et al, 2007). These findings lend support for a "processing model" whereby MMR targets O 6 -meG mismatches but fails to complete excision repair leaving single-strand gaps that persist unrepaired into the second cell cycle where they cause replication fork collapse.…”

Section: Mmr and Dna Damage Signallingmentioning

confidence: 90%

“…Mutant human and Xenopus ATRIP proteins lacking an N-terminal region required for interaction with RPA and stable DNA binding nevertheless support ATR-mediated phosphorylation of Chk1 in response to DNA damage (Ball et al, 2005;Kim et al, 2005), and TopBP1 has been postulated to be a direct activator of ATR via specific protein-protein interactions (Kumagai et al, 2006). Understanding why O 6 -meG poses a block to gap repair in the MMR pathway is an important unanswered question as it does not appear to pose a block to replication per se (Mojas et al, 2007).…”

Section: Mmr and Dna Damage Signallingmentioning

confidence: 99%

DNA mismatch repair: Molecular mechanism, cancer, and ageing

Hsieh

Yamane

2008

Mechanisms of Ageing and Development

387

359

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DNA mismatch repair (MMR) proteins are ubiquitous players in a diverse array of important cellular functions. In its role in post-replication repair, MMR safeguards the genome correcting base mispairs arising as a result of replication errors. Loss of MMR results in greatly increased rates of spontaneous mutation in organisms ranging from bacteria to humans. Mutations in MMR genes cause hereditary nonpolyposis colorectal cancer, and loss of MMR is associated with a significant fraction of sporadic cancers. Given its prominence in mutation avoidance and its ability to target a range of DNA lesions, MMR has been under investigation in studies of ageing mechanisms. This review summarizes what is known about the molecular details of the MMR pathway and the role of MMR proteins in cancer susceptibility and ageing.

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“…Upon encountering a mismatch, the MSH heterodimers recruit another heterodimer composed of mutator L homolog 1 and postmeiotic segregation increased 2 (MLH1/PMS2) to coordinate downstream repair events (1,2). Exposure to certain DNA-damaging agents, such as methylating agents and the nucleotide analog 6-thioguanine (6TG), creates lesions in the genome that give rise to mismatches when replicated (3,4). The DNA MMR system recognizes these mismatches and induces cell death to remove them.…”

mentioning

confidence: 99%

Oligonucleotide-directed mutagenesis screen to identify pathogenic Lynch syndrome-associated MSH2 DNA mismatch repair gene variants

Houlleberghs

Dekker

Lantermans

et al. 2016

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

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Single-stranded DNA oligonucleotides can achieve targeted base-pair substitution with modest efficiency but high precision. We show that "oligo targeting" can be used effectively to study missense mutations in DNA mismatch repair (MMR) genes. Inherited inactivating mutations in DNA MMR genes are causative for the cancer predisposition Lynch syndrome (LS). Although overtly deleterious mutations in MMR genes can clearly be ascribed as the cause of LS, the functional implications of missense mutations are often unclear. We developed a genetic screen to determine the pathogenicity of these variants of uncertain significance (VUS), focusing on mutator S homolog 2 (MSH2). VUS were introduced into the endogenous Msh2 gene of mouse embryonic stem cells by oligo targeting. Subsequent selection for MMR-deficient cells using the guanine analog 6-thioguanine allowed the detection of MMR-abrogating VUS. The screen was able to distinguish weak and strong pathogenic variants from polymorphisms and was used to investigate 59 Msh2 VUS. Nineteen of the 59 VUS were identified as pathogenic. Functional assays revealed that 14 of the 19 detected variants fully abrogated MMR activity and that five of the detected variants attenuated MMR activity. Implementation of the screen in clinical practice allows proper counseling of mutation carriers and treatment of their tumors.Lynch syndrome | DNA mismatch repair | MSH2 | variants of uncertain significance | site-directed mutagenesis T he DNA mismatch repair (MMR) system is essential for genome fidelity: It corrects mismatches that may arise during erroneous DNA replication and induces apoptosis if adducts caused by certain DNA-damaging agents cannot be repaired. Newly replicated DNA is scanned for base-base mispairings and loops of unpaired bases by heterodimers composed of MMR proteins mutator S homolog 2 and 6 (MSH2/MSH6) or mutator S homolog 2 and 3 (MSH2/MSH3), respectively. Upon encountering a mismatch, the MSH heterodimers recruit another heterodimer composed of mutator L homolog 1 and postmeiotic segregation increased 2 (MLH1/PMS2) to coordinate downstream repair events (1, 2). Exposure to certain DNA-damaging agents, such as methylating agents and the nucleotide analog 6-thioguanine (6TG), creates lesions in the genome that give rise to mismatches when replicated (3, 4). The DNA MMR system recognizes these mismatches and induces cell death to remove them. Several models propose how DNA MMR activates cell death. One model suggests that DNA MMR recognizes the mismatch and repetitively removes the incorporated nucleotide rather than the lesion itself, creating a cycle of futile repair which ultimately leads to DNA breakage and cell death (3). Another possibility is that MSH2/MSH6 and MLH1/PMS2 bind at the site of the damaged base and act as molecular scaffolds that activate downstream DNA damage-response pathways that result in apoptosis (5, 6). In the absence of a functional DNA MMR system, cells have an increased rate of spontaneous mutagenesis and elevated resistance to DNA-methyla...

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Mismatch repair-dependent processing of methylation damage gives rise to persistent single-stranded gaps in newly replicated DNA

Abstract: [Keywords: DNA repair; DNA replication; methylating agents; mismatch repair; replication intermediates] Supplemental material is available at http://www.genesdev.org.

Cited by 159 publications

References 42 publications

Temozolomide- and fotemustine-induced apoptosis in human malignant melanoma cells: response related to MGMT, MMR, DSBs, and p53

Temozolomide- and fotemustine-induced apoptosis in human malignant melanoma cells: response related to MGMT, MMR, DSBs, and p53

DNA mismatch repair: Molecular mechanism, cancer, and ageing

Oligonucleotide-directed mutagenesis screen to identify pathogenic Lynch syndrome-associated MSH2 DNA mismatch repair gene variants

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