When aqueous solutions of DNA were treated with 10-500 grays of gamma-rays, the imidazole rings of some adenine and guanine residues underwent scission, resulting in the conversion of these purines to formamidopyrimidines. It was found that formamidopyrimidine-DNA glycosylase, known to remove imidazole-ring-opened 7-methylguanine from DNA, did not excise the radiation-induced non-alkylated form...

Three peaks of methyltransferase activity specific for MNNG alkylated DNA have been identified from extracts of chemically adapted M. luteus. They are designated as TI to TIII in order to their elution from a Sephadex G-75 column. The first one of these peaks has been purified to homogeneity. TI, is an inducible, unusually salt resistant, heat labile protein which corrects O6-methylguanine in a...

aim :  to evaluate the association of dnmt1 and mgmt amino acid substitution polymorphisms and colorectal cancer in iranian population. background : the mgmt and dnmt1 are two important methyltransferase enzymes. amino acid substitution polymorphisms in mgmt and dnmt1 genes may be associated with the genetic susceptibility to sporadic colorectal cancer. patients and methods : we assessed eight ...

The enzyme O6-methylguanine-DNA methyltransferase repairs alkylation-induced DNA damage, O6-methylguanine and O4-methylthymine, the former being formed more frequently. Previously, by means of gene targeting, we generated mice in which alleles for methyltransferase were disrupted. We now use these mouse lines, which are totally deficient in methyltransferase activity, to examine protective effe...

Glioblastoma (GB) is one of the most lethal forms of cancer, with an invasive growth pattern that requires the use of adjuvant therapies, including chemotherapy and radiation, to prolong survival. Temozolomide (TMZ) is an oral chemotherapy with a limited side effect profile that has become the standard of care in GB treatment. While TMZ has made an impact on survival, tumor recurrence and TMZ r...

Female adnexal tumor of probable Wolffian origin (FATWO) is a rare disease entity that arises from the mesonephric duct system. FATWO is different than other gynecological cancers in terms of embryology. Here, we describe the case of a 52-year-old woman with malignant FATWO. The patient underwent explorative laparotomy and surgical staging after a frozen section revealed malignancy. Detailed ex...

3-Methyladenine-DNA glycosylase activities have been identified in all eukaryotic cell systems studied. Some of the results from these studies are reviewed here. The enzymes possess molecular weights between 24 X 10(3) and 34 X 10(3), they have a broad pH optimum at approximately pH 8, require double-stranded DNA and act in the absence of any cofactors. The enzyme can excise several different m...

The cytotoxic effects of alkylating agents are strongly attenuated by cellular DNA repair processes, necessitating a clear understanding of the repair mechanisms. Simple methylating agents form adducts at N- and O-atoms. N-methylations are removed by base excision repair, AlkB homologues, or nucleotide excision repair (NER). O(6)-methylguanine (MeG), which can eventually become cytotoxic and mu...

Lymphocytes from patients with various diseases associated with autoimmunity showed both impaired capacity to repair O6-methylguanine (a powerful, promutagenic, directly miscoding base lesion) and increased sensitivity to the cytocidal effects of cellular methylation by N-methyl-N-nitrosourea (MNU) compared with normal controls and patients with other disorders. Defective repair of O6-methylgua...