You are not currently logged in.
Access JSTOR through your library or other institution:
If You Use a Screen ReaderThis content is available through Read Online (Free) program, which relies on page scans. Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
In situ Enzymatic Reclosure of Opened Imidazole Rings of Purines in DNA Damaged by γ -irradiation
Christopher J. Chetsanga and Cheryl Grigorian
Proceedings of the National Academy of Sciences of the United States of America
Vol. 82, No. 3 (Feb. 1, 1985), pp. 633-637
Published by: National Academy of Sciences
Stable URL: http://www.jstor.org/stable/25324
Page Count: 5
Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
Preview not available
When aqueous solutions of DNA were treated with 10-500 grays of γ -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 formamidopyrimidines formed from adenine and guanine. The repair of these ring-opened purines was found to involve an enzymatic recyclizing of the opened imidazole ring that effects a restoration of the C-8 to N-9 bond. The enzyme, purine imidazole-ring cyclase reclosed the imidazole rings of 90% of ring-opened adenine or guanine, but did not close the opened imidazole ring of 7-methylguanine-derived formamidopyrimidine in DNA.
Proceedings of the National Academy of Sciences of the United States of America © 1985 National Academy of Sciences