DNA breakage, repair and lethality after 125I decay in rec+ and recA strains of Escherichia coli.
Int J Radiat Biol Relat Stud Phys Chem Med
; 29(1): 37-50, 1976 Jan.
Article
em En
| MEDLINE
| ID: mdl-773870
ABSTRACT
Iodine-125 decays by electron capture and is known to cause extensive molecular fragmentation via the Augur effect. 125I was incorporated into the DNA of exponentially-growing E. coli K12 AB2487, a recA mutant, and E. coli K12 AB2497, the corresponding rec+ strain, as 5-iododeoxyuridine (IUdR), an analogue of thymidine. Radioactive bacteria were stored at - 196 degrees C, and samples were periodically assayed for loss of viability and for the induction of double-strand breaks (DSBs) in DNA. Each 125I decay in the DNA of either strain induces one DSB, i.e. alpha(DSB) = 1.0. For the recA strain, alpha(lethal) = 0.9 and for the rec+ strain, 0.4. Assays for biological repair of DSBs, involving incubation of thawed samples in growth-medium at 37 degrees C before the extraction of DNA, demonstrate significant repair of 125I-induced DSBs by rec+ cells but none by recA cells. For small numbers of decays, there is approximately a 11 correlation, for either strain, between lethal decays and post-incubation residual DSBs. Comparison with data for larger numbers of decays indicates that a typical rec+ cell can repair no more than three to four DSBs per completed genome (2.5 x 10(9) daltons).
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Base de dados:
MEDLINE
Assunto principal:
Radiogenética
/
DNA Bacteriano
/
Reparo do DNA
/
Escherichia coli
/
Radioisótopos do Iodo
Idioma:
En
Ano de publicação:
1976
Tipo de documento:
Article