Abstract:
:Viscoelastometric measurements of DNA from gamma-irradiated bacteria were used to identify the induction of double-strand breaks ( DSBs ) in the chromosome of Escherichia coli. It is shown by means of inhibitors of repair endonucleases and different repair mutants that most DSBs in DNA of E. coli, gamma-irradiated in buffer, arise from enzymatic incision of primary gamma-damages; therefore, previous conclusions regarding DSB repair must be reconsidered. Based on these results, much of the reparable damage is single-strand breaks, and this damage can initiate formation of gaps and ultimately, when repair is insufficient, generation of enzymatically caused DSBs . After extensive repair, the first residual DSB in the E. coli chromosome is generated at approximately 160 Gray (Gy), which corresponds to the D37 dose. We propose that DSBs induced directly by gamma-irradiation are not repaired in wild-type strains. In a recently isolated gamma-resistant strain, E. coli Gamr444 , the dose required for observation of DSB after postirradiation incubation is 1,000 Gy, which corresponds to the D37 of the strain. The resistance is proposed to be due to an ability to repair genuine DSBs .
journal_name
Biophys Jjournal_title
Biophysical journalauthors
Bresler SE,Noskin LA,Suslov AVdoi
10.1016/S0006-3495(84)84218-6subject
Has Abstractpub_date
1984-04-01 00:00:00pages
749-54issue
4eissn
0006-3495issn
1542-0086pii
S0006-3495(84)84218-6journal_volume
45pub_type
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