Repair of uracil residues closely spaced on the opposite strands of plasmid DNA results in double-strand break and deletion formation - PubMed (original) (raw)

. 1991 Mar;225(3):448-52.

doi: 10.1007/BF00261686.

Affiliations

Repair of uracil residues closely spaced on the opposite strands of plasmid DNA results in double-strand break and deletion formation

G L Dianov et al. Mol Gen Genet. 1991 Mar.

Abstract

The role of closely spaced lesions on both DNA strands in the induction of double-strand breaks and formation of deletions was studied. For this purpose a polylinker sequence flanked by 165 bp direct repeats was inserted within the tet gene of pBR327. This plasmid was used to construct DNA containing one or two uracil residues which replaced cytosine residues in the KpnI restriction site of the polylinker. Incubation of the plasmid DNA construct with Escherichia coli cell-free extracts showed that double-strand breaks occurred as a result of excision repair of the opposing uracil residues by uracil-DNA glycosylase (in extracts from ung+ but not in extracts from ung- E. coli strains). Recombination of direct repeats, induced by double-strand breakage of plasmid DNA, can lead to the deletion of the polylinker and of one of the direct repeats, thus restoring the tet+ gene function which can be detected by the appearance of tetracycline-resistant colonies of transformants. Transformation of E. coli cells with single or double uracil-containing DNAs demonstrated that DNA containing two closely spaced uracil residues was tenfold more effective in the induction of deletions than DNA containing only a single uracil residue. The frequency of deletions is increased tenfold in an ung+ E. coli strain in comparison with an ung- strain, suggesting that deletions are induced by double-strand breakage of plasmid DNA which occurs in vivo as a result of the excision of opposing uracil residues.

PubMed Disclaimer

Similar articles

Cited by

References

    1. Photochem Photobiol. 1968 Jan;7(1):73-86 - PubMed
    1. Dokl Akad Nauk SSSR. 1987 Sep-Oct;296(1):226-30 - PubMed
    1. Mol Cell Biol. 1984 Jun;4(6):1020-34 - PubMed
    1. Mol Gen Genet. 1991 Aug;228(1-2):209-14 - PubMed
    1. J Bacteriol. 1975 Jan;121(1):259-66 - PubMed

MeSH terms

Substances

LinkOut - more resources