In vivo replication of hepatic deoxyribonucleic acid of rats treated with dimethylnitrosamine: presence of dimethylnitrosamine-induced O6-methylguanine, N7-methylguanine, and N3-methyladenine in the replicated hybrid deoxyribonucleic acid

Abanobi, Samuel E.; Columbano, Amedeo; Mulivor, R.A.; Rajalakshmi, S.; Sarma, D.S.R.

doi:10.1021/bi00548a018

Cited by 25 publications

(10 citation statements)

References 39 publications

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“…It has been shown that pyrimidine dimers are blocks to both replication (36) and transcription (37); therefore, their removal from active genes may be necessary to ensure cell survival. N-methylpurines, on the other hand, do not completely block replication (38), and they have not been well characterized in terms of their effects on transcription in mammalian cells. If they have little effect on the process of gene expression, then their rapid repair in actively transcribed sequences would be less critical to survival.…”

Section: Discussionmentioning

confidence: 99%

Repair of N-methylpurines in specific DNA sequences in Chinese hamster ovary cells: absence of strand specificity in the dihydrofolate reductase gene.

Scicchitano

Hanawalt

1989

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

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We have developed a quantitative method for examining the removal ofN-methylpurines from specific genes to investigate their possible differential repair throughout the genome. Chinese hamster ovary cells were exposed to dimethyl sulfate, and the isolated DNA was treated with an appropriate restriction endonuclease. The DNA was heated to convert remaining N-methylpurines to apurinic sites to render them alkaline-labile. Duplicate samples heated in the presence of methoxyamine to protect the apurinic sites from alkaline hydrolysis provided controls to assess total DNA. After alkaline hydrolysis, agarose gel electrophoresis, Southern transfer, and probing for the fragment of interest, the ratios of band intensities of the test DNA sample to its methoxyamine-treated control counterpart were calculated to yield the percentage of fragments containing no alkaline-labile sites. The frequency of N-methylpurines was measured at different times after dimethyl sulfate treatment to study repair. We found no differences between the rates of repair of N-methylpurines in the active dihydrofolate reductase gene and a nontranscribed region located downstream from it in treated cells. Also, similar rates of repair were observed in the transcribed and nontranscribed strands of the gene, in contrast to previous results for the removal of cyclobutane pyrimidine dimers. Thus, there does not appear to be a coupling of N-methylpurine repair to transcription in Chinese hamster ovary cells. However, the repair in the dihydrofolate reductase domain appears to be somewhat more efficient than that in the genome overall. Our method permits the quantifying at the defined gene level of abasic sites or of any DNA adduct that can be converted to them.The excision-repair of structure-distorting DNA lesions in mammalian chromatin is generally heterogeneous (reviewed in refs. 1-3). Cyclobutane pyrimidine dimers are excised rapidly from the active dihydrofolate reductase (DHFR) gene but persist in the bulk DNA in UV-irradiated Chinese hamster ovary (CHO) cells (4). Furthermore, efficient DNA repair is selective for the transcribed strand of the DHFR gene (5). Some bulky chemical DNA adducts also exhibit differential repair in mammalian cells, including aflatoxin B1 and psoralen photoadducts, which are removed less efficiently from the unexpressed a-satellite DNA sequences than from the bulk DNA in African green monkey cells (6-8).Within the DHFR gene in human cells, the interstrand cross-linking of DNA by psoralen diadducts is repaired at a faster rate than are psoralen monoadducts in the same region (9). Thus, efficiency of DNA repair may be affected by a variety of factors, including the nature of the damage, its location within the genome, the state of expression of the affected DNA sequences, and the chromatin configuration of the region under study.Simple methylating agents, such as dimethyl sulfate (DMS), produce a variety ofdamaged bases in DNA of which 7-methylguanine and 3-methyladenine constitute approximately 90%o of the alteratio...

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Section: Discussionmentioning

confidence: 99%

Repair of N-methylpurines in specific DNA sequences in Chinese hamster ovary cells: absence of strand specificity in the dihydrofolate reductase gene.

Scicchitano

Hanawalt

1989

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

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“…The cultures were mixed with DMS to give a final concentration of 0.05% (v/v). After 5 min of incubation at room temperature, the cells were washed twice with either ice-cold 2% glucose or 2% galactose and resuspended in the same solutions containing 100 mM hydroxyurea to prevent DNA replication during repair incubation (20). One-tenth volume of a solution containing 10% yeast extract and 20% peptone was added to the DMS-treated cultures.…”

Section: Methodsmentioning

confidence: 99%

Base Excision Repair of N-Methylpurines in a Yeast Minichromosome

Smerdon

1999

Journal of Biological Chemistry

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Base excision repair of dimethyl sulfate induced Nmethylpurines (NMPs) was measured in a yeast minichromosome that has a galactose-inducible GAL1: URA3 fusion gene, a constitutively expressed HIS3 gene, and varied regions of chromatin structure. Removal rates of NMPs varied dramatically (>20-fold) at different sites along three selected fragments encompassing a total length of 1775 base pairs. Repair of NMPs was not coupled to transcription, because the transcribed strands of HIS3 and induced GAL1:URA3 were not repaired faster than the nontranscribed strands. However, the repair rate of NMPs was significantly affected by the nearest neighbor nucleotides. Slow repair occurred at NMPs between purines, especially guanines, whereas fast repair occurred at NMPs between pyrimidines. NMPs between a purine and pyrimidine were repaired at moderate rates. Moreover, a rough correlation between nucleosome positions and repair rates exists in some but not all regions that were analyzed.Subtle alterations in DNA molecules, such as oxidized or alkylated bases, are repaired by the base excision repair (BER) 1 pathway (reviewed in Refs. 1 and 2). BER is initiated by specific DNA glycosylases that release the damaged base. There are two families of alkylated base DNA glycosylases (3). Although their primary sequences and three-dimensional structures are unrelated, they may have common themes in recognition of alkylated bases and catalysis of glycosylic bond cleavage (3). Crystal structures of the human AAG protein (3) and the Escherichia coli AlkA protein (4, 5) suggest that the glycosylases flip the target base out of the DNA duplex into the active site cleft of the enzymes. The "flipping out" may occur in a later step during recognition and/or incision of damaged bases (6).Alkylation damage to DNA occurs frequently in nature and can be introduced either by alkylating agents present in the environment or by erroneous alkylation induced by the natural methyl donor S-adenosyl-methione (7). Simple methylating agents such as dimethyl sulfate (DMS) produce a variety of damaged bases in DNA of which N-methylpurines (N 7 -methylguanine and N 3 -methyladenine) or NMPs constitute approximately 90% of the alterations (8). In Saccharomyces cerevisiae, the repair of NMPs occurs mainly through the BER pathway, although nucleotide excision repair (NER) may play a role if the BER pathway is abolished (9). Initiation of this pathway in S. cerevisiae is by the action of the small (34 kDa) protein MAG DNA glycosylase (10).Although the repair of thymine glycols is coupled to transcription in both yeast and mammalian cells (11,12), a link between transcription and BER of other lesions has not been well established. It was found that the alkali-labile sites (representing NMPs) induced by methylnitrosourea are preferentially repaired within the active insulin gene of rat insulinoma cells (13). However, no preferential repair of these lesions induced by DMS was found in the actively transcribed DHFR gene of Chinese hamster ovary cells (14 -16) or in t...

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“…This view is supported by the observations that templates containing 06-methylguanine direct RNA polymerase (6) and DNA polymerase I (7) to incorporate inappropriate ribonucleoside 5'-triphosphates and deoxyribonucleoside 5'-triphosphates, respectively. Recently, DNA damaged by dimethylnitrosamine has been demonstrated to permit replication in vivo (8).…”

Section: Introductionmentioning

confidence: 99%

A system in mouse liver for the repair of O⁶-methylguanine lesions in methylated DNA

1981

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An activity from mouse liver with catalyzes the disappearance of O6-methylguanine from DNA methylated with methylnitrosourea has been partially purified by ammonium sulfate fractionation and DNA-cellulose chromatography. The activity does not require divalent metal ions and is not affected by EDTA. It is specific for the repair of O6-methylguanine lesions and does not affect the removal of 7-methylguanine, 7-methyladenine or 3-methyladenine. The disappearance of O6-methylguanine is linear with respect to the concentration of protein and is dependent on incubation temperature. The kinetics and substrate dependence experiments suggest that the protein factor is product-inactivated. Amino acid analysis of hydrolysates of protein obtained after incubation of methylated DNA with the protein factor indicates the presence of radiolabeled S-methyl-L-cysteine, suggesting that during the repair of O6-methylguanine from methylated DNA, the methyl group is transferred to a sulfhydryl of a cysteine residue of a protein. This represents the first such demonstration in a mammalian system.

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In vivo replication of hepatic deoxyribonucleic acid of rats treated with dimethylnitrosamine: presence of dimethylnitrosamine-induced O6-methylguanine, N7-methylguanine, and N3-methyladenine in the replicated hybrid deoxyribonucleic acid

Cited by 25 publications

References 39 publications

Repair of N-methylpurines in specific DNA sequences in Chinese hamster ovary cells: absence of strand specificity in the dihydrofolate reductase gene.

Repair of N-methylpurines in specific DNA sequences in Chinese hamster ovary cells: absence of strand specificity in the dihydrofolate reductase gene.

Base Excision Repair of N-Methylpurines in a Yeast Minichromosome

A system in mouse liver for the repair of O⁶-methylguanine lesions in methylated DNA

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In vivo replication of hepatic deoxyribonucleic acid of rats treated with dimethylnitrosamine: presence of dimethylnitrosamine-induced O6-methylguanine, N7-methylguanine, and N3-methyladenine in the replicated hybrid deoxyribonucleic acid

Cited by 25 publications

References 39 publications

Repair of N-methylpurines in specific DNA sequences in Chinese hamster ovary cells: absence of strand specificity in the dihydrofolate reductase gene.

Repair of N-methylpurines in specific DNA sequences in Chinese hamster ovary cells: absence of strand specificity in the dihydrofolate reductase gene.

Base Excision Repair of N-Methylpurines in a Yeast Minichromosome

A system in mouse liver for the repair of O6-methylguanine lesions in methylated DNA

Contact Info

Product

Resources

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A system in mouse liver for the repair of O⁶-methylguanine lesions in methylated DNA