Overexpression of human DNA repair protein <i>N</i>-methylpurine-DNA glycosylase results in the increased removal of <i>N</i>-methylpurines in DNA without a concomitant increase in resistance to alkylating agents in Chinese hamster ovary cells

Ibeanu, Gordon C.; Hartenstein, Bettina; Dunn, William C.; Ch’ang, Lan-Yang; Hofmann, Edward R.; Coquerelle, Thérèse; Mitra, Sankar; Kaina, Bernd

doi:10.1093/carcin/13.11.1989

Cited by 58 publications

(38 citation statements)

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“…Overexpression of methyl-specific DNA glycosylases has been reported to have varying effects in mammalian cells, ranging from no effect to eliciting an increase in or a decrease in sensitivity to alkylating agents (Ibeanu et al, 1992;Klungland et al, 1992;Habraken and Laval, 1993). We and Table 1) or with media for 6, 12, 24, and 48 h. These cells were also treated with 15 M ETO or media for 24 h. After drug treatment, the cell pellet was resuspended in 1ϫ cell lysis buffer, and cytosolic extract was used for the assay of caspase-3 activation.…”

Section: Discussionmentioning

confidence: 99%

Human Methyl Purine DNA Glycosylase and DNA Polymerase β Expression Collectively Predict Sensitivity to Temozolomide

Trivedi

Wang²,

Jelezcova³

et al. 2008

Mol Pharmacol

103

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Overexpression of N-methylpurine DNA glycosylase (MPG) has been suggested as a possible gene therapy approach to sensitize tumor cells to the cell-killing effects of temozolomide, an imidazotetrazine-class chemotherapeutic alkylating agent. In the present study, we show that both elevated MPG expression and short hairpin RNA-mediated loss of DNA polymerase ␤ (Pol ␤) expression in human breast cancer cells increases cellular sensitivity to temozolomide. Resistance to temozolomide is restored by complementation of either wild-type human Pol ␤ or human Pol ␤ with an inactivating mutation specific to the polymerase active site yet functional for 5Ј-deoxyribosephosphate (5ЈdRP) lyase activity. These genetic and cellular studies uniquely demonstrate that overexpression of MPG causes an imbalance in base excision repair (BER), leading to an accumulation of cytotoxic 5ЈdRP lesions, and that the 5ЈdRP lyase activity of Pol ␤ is required to restore resistance to temozolomide. These results imply that Pol ␤-dependent 5ЈdRP lyase activity is the rate-limiting step in BER in these cells and suggests that BER is a tightly balanced pathway for the repair of alkylated bases such as N7-methylguanine and N3-methyladenine. Furthermore, we find that 5ЈdRP-mediated cell death is independent of caspase-3 activation and does not induce the formation of autophagosomes, as measured by green fluorescent protein-light chain 3 localization. The experiments presented herein suggest that it will be important to investigate whether an active BER pathway could be partially responsible for the temozolomide-mediated resistance seen in some tumors and that balanced BER protein expression and overall BER capacity may help predict sensitivity to temozolomide.Base excision repair (BER) is the predominant pathway for the repair of base damage mediated by endogenous and exogenous stressors (Lindahl and Wood, 1999;Almeida and Sobol, 2007). The repair of DNA bases damaged by alkylation is initiated in mammalian cells by N-methylpurine DNA glycosylase (MPG), also known as alkyladenine DNA glycosylase (Wood et al., 2001). The majority of repair that is initiated by MPG occurs via short-patch BER, a mechanism whereby only one nucleotide is replaced. Once the modified base is removed by MPG, the resulting abasic site is hydrolyzed by AP endonuclease (APE1) (Wood et al., 2001), catalyzing the incision of the damaged strand, leaving a 3ЈOH and a 5Ј-deoxyribose-phosphate moiety (5ЈdRP) at the margins of the repair site. DNA polymerase ␤ (Pol ␤) subsequently hydrolyzes the 5ЈdRP moiety and fills the single nucleotide gap, preparing the strand for ligation by either DNA ligase I or a complex of DNA ligase III␣ and XRCC1.As with many DNA repair processes, BER functions via a series of repair complexes that assemble at the site of the DNA lesion. For the repair of DNA damaged by alkylation, MPG, APE1, Pol ␤, and XRCC1 are essential, with little evidence of effective complementary repair capacity (Almeida and Sobol, 2007). This would suggest that inhibition...

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Section: Discussionmentioning

confidence: 99%

Human Methyl Purine DNA Glycosylase and DNA Polymerase β Expression Collectively Predict Sensitivity to Temozolomide

Trivedi

Wang²,

Jelezcova³

et al. 2008

Mol Pharmacol

103

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“…For example, in yeast, when BER is imbalanced by an excess of abasic sites (generated by over-expression N-methylpurine-DNA glycosylases, MPG), the rate of spontaneous mutation is increased signi®cantly (Chakravarti et al, 1991;Berdal et al, 1998;Glassner et al, 1998;Lau et al, 2000). Chinese hamster ovary cells over-expressing human MPG (a broad spectrum glycosylase), however, when exposed to methylating agents, did not show increased mutagenesis but showed inhibition of DNA synthesis, chromosomal aberrations and DNA breaks (Ibeanu et al, 1992;Coquerelle et al, 1995). On the other hand, Chinese hamster V79 cells over-expressing bacterial tag gene (removes only 3-methyladenine) were more resistant to cytotoxic and mutagenic e ects of methylating agents (Klugland et al, 1992).…”

Section: Discussionmentioning

confidence: 99%

Evidence that a burst of DNA depurination in SENCAR mouse skin induces error-prone repair and forms mutations in the H-ras gene

et al. 2001

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“…The enzyme's precise role in protecting cells from the cytotoxic effects of alkylating agents is still controversial (Klungland et al, 1992;Habraken and Laval, 1993;Imperatori et al, 1994;Ibeanu et al, 1992;Matijasevic et al, 1993). Klungland et al (1992 reported that V79 hamster lung fibroblasts and murine haematopoietic cells permanently expressing the tag gene showed increased resistance to killing by methylmethanesulphonate (MMS) and methylnitrosurea (MNU).…”

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confidence: 99%

3-methyladenine-DNA-glycosylase and O6-alkyl guanine-DNA-alkyltransferase activities and sensitivity to alkylating agents in human cancer cell lines

Damia

Imperatori²,

Citti³

et al. 1996

Br J Cancer

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Summary The activities and the expression of 3-methyladenine glycosylase (3-meAde gly) and O6-alkylguanine-DNA-alkyltransferase (06ATase) were investigated in ten human cancer cell lines. Both 3-meAde gly and 06ATase activities were variable among different cell lines. mRNA levels of the 06ATase gene, appeared to be related to the content of 06ATase in different cell lines, whereas no apparent correlation was found between mRNA of 3-meAde gly and the enzymatic activity. No correlation was found between the activity of the two enzymes and the sensitivity to alkylating agents of different structures such as CC-1065, tallimustine, dimethylsulphate (DMSO), N-methyl-N'-nitro-N-ntirosoguanidine (MNNG), cis-diamminedichloroplatinum (cDDP) and melphalan (L-PAM). The most striking finding of this study is that a correlation exists between the activity of O6ATase and 3-meAde gly in the various cell lines investigated (P<0.01), suggesting a common mechanism of regulation of two DNA repair enzymes.

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Overexpression of human DNA repair protein N-methylpurine-DNA glycosylase results in the increased removal of N-methylpurines in DNA without a concomitant increase in resistance to alkylating agents in Chinese hamster ovary cells

Cited by 58 publications

References 0 publications

Human Methyl Purine DNA Glycosylase and DNA Polymerase β Expression Collectively Predict Sensitivity to Temozolomide

Human Methyl Purine DNA Glycosylase and DNA Polymerase β Expression Collectively Predict Sensitivity to Temozolomide

Evidence that a burst of DNA depurination in SENCAR mouse skin induces error-prone repair and forms mutations in the H-ras gene

3-methyladenine-DNA-glycosylase and O6-alkyl guanine-DNA-alkyltransferase activities and sensitivity to alkylating agents in human cancer cell lines

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