Search results for "Endonuclease"

Covalent DNA adducts formed by benzo[c]chrysene in mouse epidermis and by benzo[c]chrysene fjord-region diol epoxides reacted with DNA and polynucleo…

1997

The metabolic activation in mouse skin of benzo[c]chrysene (B[c]C), a weakly carcinogenic polycyclic aromatic hydrocarbon (PAH) present in coal tar and crude oil, was investigated. Male Parkes mice were treated topically with 0.5 mumol of B[c]C, and DNA was isolated from the treated areas of skin at various times after treatment and analyzed by 32P-postlabeling. Seven adduct spots were detected, at a maximum level of 0.89 fmol of adducts/microgram of DNA. Four B[c]C-DNA adducts persisted in skin for at least 3 weeks. Treatment of mice with 0.5 mumol of the optically pure putative proximate carcinogens (+)- and (-)-trans-benzo[c]chrysene-9,10-dihydrodiols [(+)- and (-)-B[c]C-diols] led to th…

Nuclear Translocation of Mismatch Repair Proteins MSH2 and MSH6 as a Response of Cells to Alkylating Agents

2000

Mammalian mismatch repair has been implicated in mismatch correction, the prevention of mutagenesis and cancer, and the induction of genotoxicity and apoptosis. Here, we show that treatment of cells specifically with agents inducing O(6)-methylguanine in DNA, such as N-methyl-N'-nitro-N-nitrosoguanidine and N-methyl-N-nitrosourea, elevates the level of MSH2 and MSH6 and increases GT mismatch binding activity in the nucleus. This inducible response occurs immediately after alkylation, is long-lasting and dose-dependent, and results from translocation of the preformed MutSalpha complex (composed of MSH2 and MSH6) from the cytoplasm into the nucleus. It is not caused by an increase in MSH2 gen…

DNA damage profiles induced by oxidizing agents

1995

Molecular modes of action of cantharidin in tumor cells

2005

Cancer chemotherapy is often limited by patient's toxicity and tumor drug resistance indicating that new drug development and modification of existing drugs is critical for improving the therapeutic response. Traditional Chinese medicine is a rich source of potential anticancer agents. In particular, cantharidin (CAN), the active principle ingredient from the blister beetle, Mylabris, has anti-tumor activity, but the cytotoxic mechanism is unknown. In leukemia cells, cantharidin induces apoptosis by a p53-dependent mechanism. Cantharidin causes both DNA single- and double-strand breaks. Colony-forming assays with knockout and transfectant cells lines showed that DNA polymerase beta, but not…

Nucleotide excision repair of abasic DNA lesions

2019

AbstractApurinic/apyrimidinic (AP) sites are a class of highly mutagenic and toxic DNA lesions arising in the genome from a number of exogenous and endogenous sources. Repair of AP lesions takes place predominantly by the base excision pathway (BER). However, among chemically heterogeneous AP lesions formed in DNA, some are resistant to the endonuclease APE1 and thus refractory to BER. Here, we employed two types of reporter constructs accommodating synthetic APE1-resistant AP lesions to investigate the auxiliary repair mechanisms in human cells. By combined analyses of recovery of the transcription rate and suppression of transcriptional mutagenesis at specifically positioned AP lesions, w…

c-Fos is required for excision repair of UV-light induced DNA lesions by triggering the re-synthesis of XPF

2006

Cells deficient in c-Fos are hypersensitive to ultraviolet (UV-C) light. Here we demonstrate that mouse embryonic fibroblasts lacking c-Fos (fos-/-) are defective in the repair of UV-C induced DNA lesions. They show a decreased rate of sealing of repair-mediated DNA strand breaks and are unable to remove cyclobutane pyrimidine dimers from DNA. A search for genes responsible for the DNA repair defect revealed that upon UV-C treatment the level of xpf and xpg mRNA declined but, in contrast to the wild type (wt), did not recover in fos-/- cells. The observed decline in xpf and xpg mRNA is due to impaired re-synthesis, as shown by experiments using actinomycin D. Block of xpf transcription resu…

DNA damage by peroxynitrite characterized with DNA repair enzymes.

1996

The DNA damage induced by peroxynitrite in isolated bacteriophage PM2 DNA was characterized by means of several repair enzymes with defined substrate specificities. Similar results were obtained with peroxynitrite itself and with 3-morpholinosydnonimine (SIN-1), a compound generating the precursors of peroxynitrite, nitric oxide and superoxide. A high number of base modifications sensitive to Fpg protein which, according to HPLC analysis, were mostly 8-hydroxyguanine residues, and half as many single-strand breaks were observed, while the numbers of oxidized pyrimidines (sensitive to endonuclease III) and of sites of base loss (sensitive to exonuclease III or T4 endonuclease V) were relativ…

Fen1 is induced p53 dependently and involved in the recovery from UV-light-induced replication inhibition.

2005

Mouse embryonic fibroblasts (MEFs) that lack p53 are hypersensitive to the cytotoxic and genotoxic effect of ultraviolet (UV-C) light. They also display a defect in the recovery from UV-C-induced DNA replication inhibition. An enzyme involved in processing stalled DNA replication forks is flap endonuclease 1 (Fen1). Gene expression profiling of UV-C-irradiated MEFs revealed fen1 to be upregulated, which was confirmed by RT-PCR and Western blot experiments. Increased Fen1 levels upon UV-C exposure are due to transcriptional activation, as revealed by inhibitor studies. Fen1 induction was dose- and time-dependent; it occurred on protein level already 3 h after irradiation. Induction of Fen1 b…

Identification and typing of food-borne Staphylococcus aureus by PCR-based techniques.

2005

Abstract The possibility of using PCR for rapid identification of food-borne Staphylococcus aureus isolates was evaluated as an alternative to the API-Staph system. A total of 158 strains, 15 S. aureus , 12 other staphylococcal species, and 131 isolates recovered from 164 food samples were studied. They were phenotypically characterized by API-Staph profiles and tested for PCR amplification with specific primers directed to thermonuclease ( nuc ) and enterotoxin ( sea to see ) genes. Disagreement between the PCR results and API-Staph identification was further assessed by the analysis of randomly amplified polymorphic DNA (RAPD) profiles obtained with three universal primers (M13, T3, and T…

Endoribonuclease IV. A poly(A)-specific ribonuclease from chick oviduct. 1. Purification of the enzyme.

1976

A new endoribonuclease, termed endoribonuclease IV, has been described. This enzyme has been isolated from chick oviducts and purified 15 000-fold in a 25% yield nearly to homogeneity. The nuclease, which specifically degrades poly(A), forms oligonucleotides of an average chain length of 10. These (A)-10 fragments are terminated by 3'-hydroxyl and 5'-phosphate groups. The enzyme has a pH optimum at 8.7, requires Mn2+ or Mg2+ as a cofactor, and has a molecular weight of about 45 000.