1997 Fiscal Year Final Research Report Summary
Repair of alkylation DNA damage
| Project/Area Number |
09044350
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| Research Category |
Grant-in-Aid for international Scientific Research
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| Allocation Type | Single-year Grants |
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| Section | Joint Research |
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| Research Field |
Molecular biology
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| Research Institution | Fukuoka Dental College |
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Principal Investigator |
SEKIGUCHI Mutsuo Fukuoka Dental College, Department of Biology, Professor, 歯学部, 教授 (00037342)
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| Co-Investigator(Kenkyū-buntansha) |
SANADA Masayuki Fukuoka Dental College, Department of Biology, Assistant Professor, 歯学部, 講師 (40084264)
HAYAKAWA Hiroshi Kyushu University, Faculty of Medicine, Research Associate, 医学部, 助手 (70150422)
NAKABEPPU Yuusaku Kyushu University, Medical Institute of Bioregulation, Professor, 生体防御医学研究所, 教授 (30180350)
SAKUMI Kumihiko Kyushu University, Medical Institute of Bioregulation, Research Associate, 生体防御医学研究所, 助手 (50211933)
TUZUKI Teruhisa Kyushu University, Faculty of Medicine, Professor, 医学部, 教授 (40155429)
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| Project Period (FY) |
1997
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| Keywords | alkylating agent / modified base / monoclonal antibody / gene-defective mouse / DNA repair / repair methyltransferase / gene targeting / O^6-methylguanine |
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| Research Abstract |
Gene targeting was used to obtain mice defective in the MGMT gene, encoding O^6 -methylguanine-DNA methyltransferase. These MGMT^+ mice were most sensitive to the alkylating carcinogen, methylnitrosourea (MNU) ; when varied doses of MNU were administered to 6-week-old mice and survivals at the 30th day were determined, LD_<50S> of MGMT^+ and MGMT^<+/+> mice were 20 and 240 mg/kg of body weight, respectively.
MGMT^<+/-> mice were as resistant as MGMT^<+/+> mice, but some difference in survival time was noted when the two genotypes of mice were exposed to a relatively high dose of MNU.A large number of thymic lymphomas, as well as lung adenomas, occurred in MGMT^<-/-> mice exposed to MNU at a dose of 2.5 mg/kg of body weight. In case of exposure to the same dose of drub, no or few tumors occureed in the MGMT^<+/+> and MGMT^<+/-> mice. It appears that the DNA repair methyltransferase protein protected these mice from MNU-induced tumorigenesis.
To pursue the fate ot O^6-methylguanin produced in the DNA of mouse tissues, we used monoclonal antibodies raised by the Rajewsky's group of University of Essen. This antibody preparation specifically recognizes O^6-ethylguanine as well as O^6-methylguanin. For the collaborative work, H.Hayakawa and K.Sakumi of Kyushu University visited the Essen laboratory and T.Schweer of Essen visited here in Fukuoka. We have established appropriate doses of MNU to be given to MGMT^<+/+> and MGMT^<-/-> mice and also conditions and procedures to follow changes in amounts of methylated bases in mouse tissues. A preliminary result indicates that MGMT^<-/-> mice retain a significant level of alkylated bases in DNA whereas MGMT^<+/+> mice lose these bases rather quickly.
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