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Crosstalk between repair pathways elicits double-strand breaks in alkylated DNA and implications for the action of temozolomide.

Authors :
Fuchs RP
Isogawa A
Paulo JA
Onizuka K
Takahashi T
Amunugama R
Duxin JP
Fujii S
Source :
ELife [Elife] 2021 Jul 08; Vol. 10. Date of Electronic Publication: 2021 Jul 08.
Publication Year :
2021

Abstract

Temozolomide (TMZ), a DNA methylating agent, is the primary chemotherapeutic drug used in glioblastoma treatment. TMZ induces mostly N-alkylation adducts (N7-methylguanine and N3-methyladenine) and some O <superscript>6</superscript> -methylguanine (O <superscript>6</superscript> mG) adducts. Current models propose that during DNA replication, thymine is incorporated across from O <superscript>6</superscript> mG, promoting a futile cycle of mismatch repair (MMR) that leads to DNA double-strand breaks (DSBs). To revisit the mechanism of O <superscript>6</superscript> mG processing, we reacted plasmid DNA with N-methyl-N-nitrosourea (MNU), a temozolomide mimic, and incubated it in Xenopus egg-derived extracts. We have shown that in this system, MMR proteins are enriched on MNU-treated DNA and we observed robust, MMR-dependent, repair synthesis. Our evidence also suggests that MMR, initiated at O <superscript>6</superscript> mG:C sites, is strongly stimulated in cis by repair processing of other lesions, such as N-alkylation adducts. Importantly, MNU-treated plasmids display DSBs in extracts, the frequency of which increases linearly with the square of alkylation dose. We suggest that DSBs result from two independent repair processes, one involving MMR at O <superscript>6</superscript> mG:C sites and the other involving base excision repair acting at a nearby N-alkylation adduct. We propose a new, replication-independent mechanism of action of TMZ, which operates in addition to the well-studied cell cycle-dependent mode of action.<br />Competing Interests: RF, AI, JP, KO, TT, RA, JD, SF No competing interests declared<br /> (© 2021, Fuchs et al.)

Details

Language :
English
ISSN :
2050-084X
Volume :
10
Database :
MEDLINE
Journal :
ELife
Publication Type :
Academic Journal
Accession number :
34236314
Full Text :
https://doi.org/10.7554/eLife.69544