大学院生(当時M2)松川和樹君の研究、国際科学雑誌の表紙を飾る!

国立がんセンター研究所(若林敬二博士らのグループ)との共同研究で、本分野の松川和樹君(2004年3月修士課程修了)が進めていた仕事の一部が、アメリカ化学会の雑誌「Chemical Research in Toxicology」8月13日号(Vol. 16, No. 8, 2003)に掲載され、研究内容をあしらった絵が表紙を飾りました。近年、がん細胞を殺す働きがある天然物質としてモンシロチョウからピエリシンと呼ばれるタンパク質が単離され、このタンパク質はDNA中のグアニンをモノADPリボシル化することがわかりました。このたび掲載された論文は、ADPリボシル化されたグアニンが突然変異を起すことをDNAの塩基配列レベルで示したもので、これは生物界で今まで全く知られていなかった突然変異誘発機構の発見であります。今後はモンシロチョウにおけるピエリシン存在の意義と、ヒトにおいてもDNAのADPリボシル化現象が存在するかどうかの解明が大きなテーマとなります。表紙写真と論文概要は以下。
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Chem Res Toxicol. 2003 Aug;16(8):945-52.

Analysis of HPRT and supF mutations caused by pierisin-1, a guanine specific ADP-ribosylating toxin derived from the cabbage butterfly.

Totsuka Y, Kawanishi M, Nishigaki R, Matsukawa K, Yagi T, Takamura-Enya T, Watanabe M, Sugimura T, Wakabayashi K.

Cancer Prevention Basic Research Project, National Cancer Center Research Institute, 1-1 Tsukiji 5-Chome, Chuo-ku, Tokyo 104-0045, Japan.

Pierisin-1, an ADP-ribosylating toxin derived from the cabbage butterfly, Pieris rapae, induces apoptosis in various mammalian cell lines. We recently reported that the target for ADP ribosylation by pierisin-1 is the 2'-deoxyguanosine residue in DNA. To examine whether pierisin-1 would induce mutations in mammalian cell genes, we conducted a mutational analysis for the hypoxanthine-guanine phosphoribosyltransferase (HPRT) locus in pierisin-1-treated Chinese hamster lung (CHL) cells. N(2)-(ADP-ribos-1-yl)-2'-deoxyguanosine was detected by the (32)P-postlabeling method in CHL cells after treatment with pierisin-1 at doses of 2-32 ng/mL; adduct levels were 1.1-12.0 per 10(6) nucleotides. Pierisin-1 induced mutations in the HPRT gene dose-dependently, and the frequency was 38 times higher than the control, at a dose of 32 ng/mL. To confirm that mono(ADP-ribosyl)ated dG itself leads to mutations, the pierisin-1-treated DNA of plasmid pMY189 bearing the supF gene was used for mutational analysis. The mutation frequency of the supF gene treated with 2-8 micro g/mL of pierisin-1 was 17-40-fold the control value. Mutation spectrum analysis showed that single base substitutions dominated in both HPRT and supF genes. Among these, transversions were predominant, and more than 70% of the base substitutions occurred at G:C base pairs in both genes. The most frequent mutations were G:C to C:G, followed by G:C to T:A in HPRT gene, whereas G:C to T:A transversions dominated in the supF gene. Our results indicate that pierisin-1 produced N(2)()-(ADP-ribos-1-yl)-2'-deoxyguanosine and this guanine-adduct could lead to mutations in the HPRT and supF genes. These findings could provide very useful information for understanding the biological significance of pierisin-1.

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