POSTREPLICATION REPAIR IN AN EXCISION-DEFECTIVE MUTANT OF ESCHERICHIA COLI: ULTRAVIOLET LIGHT-INDUCED INCORPORATION OF BROMODEOXYURIDINE INTO PARENTAL DNA* |
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Authors: | Ronald D Ley |
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Institution: | Division of Biological and Medical Research, Argonne National Laboratory, Argonne, Illinois 60439, U.S.A. |
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Abstract: | Abstract— Ultraviolet (UV) light-induced incorporation of bromodeoxyuridine (BrdUrd) into parental DNA of an excision-defective mutant of Escherichia coli has been observed by selective photolysis of bromouracil (BrUra)-containing regions in the parental DNA. It appears that the BrUra-containing regions occur only in that DNA which has served as a template for normal semiconservative replication. After an exposure at 254 nm which results in one pyrimidine dimer per 45times 106 daltons, incubation in BrdUrd resulted in BrUra–containing regions ? 1.5 times 104 nucleotides in length at intervals of ? 55 times 106 daltons in the parental DNA. Thus approximately one BrUra-containing region has occurred for every 1.2 pyrimidine dimers in the parental DNA. The observed incorporation of BrdUrd is interpreted in terms of a proposed model for postreplication repair in which genetic exchanges produce single-strand gaps in the parental DNA. |
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