PMID:11489847
| Citation |
Hanada, K, Yamashita, T, Shobuike, Y and Ikeda, H (2001) Role of DnaB helicase in UV-induced illegitimate recombination in Escherichia coli. J. Bacteriol. 183:4964-9 |
|---|---|
| Abstract |
To study the involvement of DNA replication in UV-induced illegitimate recombination, we examined the effect of temperature-sensitive dnaB mutations on illegitimate recombination and found that the frequency of illegitimate recombination was reduced by an elongation-deficient mutation, dnaB14, but not by an initiation-deficient mutation, dnaB252. This result indicates that DNA replication is required for UV-induced illegitimate recombination. In addition, the dnaB14 mutation also affected spontaneous or UV-induced illegitimate recombination enhanced by the recQ mutation. Nucleotide sequence analyses of the recombination junctions showed that DnaB-mediated illegitimate recombination is short homology dependent. Previously, Michel et al. (B. Michel, S. Ehrlich, and M. Uzest, EMBO J. 16:430--438, 1997) showed that thermal treatment of the temperature-sensitive dnaB8 mutant induces double-stranded breaks, implying that induction of illegitimate recombination occurs. To explain the discrepancy between the observations, we propose a model for DnaB function, in which the dnaB mutations may exhibit two types of responses, early and late responses, for double-stranded break formation. In the early response, replication forks stall at damaged DNA, resulting in the formation of double-stranded breaks, and the dnaB14 mutation reduces the double-stranded breaks shortly after temperature shift-up. On the other hand, in the late response, the arrested replication forks mediated by the dnaB8 mutation may induce double-stranded breaks after prolonged incubation. |
| Links | |
| Keywords |
Bacterial Proteins; DNA Damage; DNA Helicases/genetics; DNA Helicases/physiology; DNA, Bacterial/chemistry; DnaB Helicases; Escherichia coli/enzymology; Escherichia coli/genetics; Escherichia coli/radiation effects; Mutation; Recombination, Genetic/radiation effects; Sequence Analysis, DNA; Ultraviolet Rays |
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