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Excision of Damaged Thymine Residues from Gamma-Irradiated Poly(dA-dT) by Crude Extracts of Escherichia coli

P. V. Hariharan and P. A. Cerutti
Proceedings of the National Academy of Sciences of the United States of America
Vol. 71, No. 9 (Sep., 1974), pp. 3532-3536
Stable URL: http://www.jstor.org/stable/63825
Page Count: 5
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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.
Excision of Damaged Thymine Residues from Gamma-Irradiated Poly(dA-dT) by Crude Extracts of Escherichia coli
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Abstract

Crude extracts of E. coli endo I- and E. coli endo I-uvrA6- possess the ability to remove thymine products of the 5,6-dihydroxy-dihydrothymine type from γ -irradiated or osmium tetroxide-oxidized poly(dA-dT). It is shown that the uvrA-gene product, which is responsible for incision close to photodimers in prereplication ultraviolet repair in E. coli, is not required for, but may aid in, the excision of γ -ray products of the 5,6-dihydroxy-dihydrothymine type. Ring-damaged thymine products are also removed by E. coli extracts from osmium tetroxideoxidized poly(dA-dT), which contains only 5,6-dihydroxy-dihydrothymine but no strand breakage, indicating that product excision occurs in the absence of radiation-induced breaks. On the average, 8 to 16 nucleotides are removed from the polymer per ring-damaged thymine residue excised by extracts from both strains and for γ -irradiated and osmium tetroxide-oxidized polymer.

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