Mismatch repair in Xenopus egg extracts: DNA strand breaks act as signals rather than excision points.

Eukaryotic mismatch repair (MMR) utilizes single-strand breaks as signals to target the strand to be repaired. DNA-bound PCNA is also presumed to direct MMR. The MMR capability must be limited to a post-replicative temporal window during which the signals are available. However, both identity of the signal(s) involved in the retention of this temporal window and the mechanism that maintains the MMR capability after DNA synthesis remain unclear. Using Xenopus egg extracts, we discovered a mechanism that ensures long-term retention of the MMR capability. We show that DNA-bound PCNA induces strand-specific MMR in the absence of strand discontinuities. Strikingly, MutSα inhibited PCNA unloading through its PCNA-interacting motif, thereby extending significantly the temporal window permissive to strand-specific MMR. Our data identify DNA-bound PCNA as the signal that enables strand discrimination after the disappearance of strand discontinuities, and uncover a novel role of MutSα in the retention of the post-replicative MMR capability.

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Kinesin Kif2C in regulation of DNA double strand break dynamics and repair

eLife ◽

10.7554/elife.53402 ◽

2020 ◽

Vol 9 ◽

Cited By ~ 3

Author(s):

Songli Zhu ◽

Mohammadjavad Paydar ◽

Feifei Wang ◽

Yanqiu Li ◽

Ling Wang ◽

...

Keyword(s):

Dna Damage ◽

Mammalian Cells ◽

Strand Break ◽

Dna Double Strand Breaks ◽

Dsb Repair ◽

Strand Breaks ◽

Dna Double Strand Break ◽

Egg Extracts ◽

Xenopus Egg ◽

Xenopus Egg Extracts

DNA double strand breaks (DSBs) have detrimental effects on cell survival and genomic stability, and are related to cancer and other human diseases. In this study, we identified microtubule-depolymerizing kinesin Kif2C as a protein associated with DSB-mimicking DNA templates and known DSB repair proteins in Xenopus egg extracts and mammalian cells. The recruitment of Kif2C to DNA damage sites was dependent on both PARP and ATM activities. Kif2C knockdown or knockout led to accumulation of endogenous DNA damage, DNA damage hypersensitivity, and reduced DSB repair via both NHEJ and HR. Interestingly, Kif2C depletion, or inhibition of its microtubule depolymerase activity, reduced the mobility of DSBs, impaired the formation of DNA damage foci, and decreased the occurrence of foci fusion and resolution. Taken together, our study established Kif2C as a new player of the DNA damage response, and presented a new mechanism that governs DSB dynamics and repair.

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The Mismatch Repair System Modulates Curcumin Sensitivity through Induction of DNA Strand Breaks and Activation of G2-M Checkpoint

Molecular Cancer Therapeutics ◽

10.1158/1535-7163.mct-09-0627 ◽

2010 ◽

Vol 9 (3) ◽

pp. 558-568 ◽

Cited By ~ 21

Author(s):

Zhihua Jiang ◽

ShunQian Jin ◽

Jack C. Yalowich ◽

Kevin D. Brown ◽

Baskaran Rajasekaran

Keyword(s):

Mismatch Repair ◽

Dna Strand Breaks ◽

Repair System ◽

Strand Breaks ◽

Mismatch Repair System ◽

Dna Strand

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Crosstalk between repair pathways elicits Double-Strand Breaks in alkylated DNA: implications for the action of temozolomide

10.1101/2020.11.21.391326 ◽

2020 ◽

Author(s):

Robert P. Fuchs ◽

Asako Isogawa ◽

Joao A. Paulo ◽

Kazumitsu Onizuka ◽

Tatsuro Takahashi ◽

...

Keyword(s):

Mismatch Repair ◽

Double Strand Breaks ◽

Dna Double Strand Breaks ◽

Futile Cycle ◽

Repair Synthesis ◽

Strand Breaks ◽

Egg Extracts ◽

Established Cell ◽

Cycle Dependent ◽

Xenopus Egg Extracts

AbstractTemozolomide, 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 O6-methylguanine (O6mG). Current models propose that during DNA replication, thymine is incorporated across from O6mG, promoting a futile cycle of mismatch repair (MMR) that leads to DNA double strand breaks (DSBs). To revisit the mechanism of O6mG processing, we reacted plasmid DNA with N-Methyl-N-nitrosourea (MNU), a temozolomide mimic, and incubated it in Xenopus egg extracts. We show that in this system, mismatch repair (MMR) proteins are enriched on MNU-treated DNA and we observe robust, MMR-dependent, repair synthesis. Our evidence also suggests that MMR, initiated at O6mG: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 increased linearly with the square of alkylation dose. We suggest that DSBs result from two independent repair processes, one involving MMR at O6mG:C sites and the other involving BER acting at a nearby N-alkylation adducts. We propose a new, replication-independent mechanism of action of TMZ, that operates in addition to the well-established cell cycle dependent mode of action.

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