Single-stranded DNA gaps, tails and loops are repaired in Escherichia coli

Colin R. Campbell, David Ayares, Katherine Watkins, Robert Wolski, Raju Kucherlapati

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4 Scopus citations


Uniformly methylated heteroduplex plasmids which contained 6 mismatched regions, including loops of 24, 30, 248 and 283 nucleotides, as well as single-stranded gaps and free ends were introduced into a recombination-deficient strain of bacteria, and the products of repair were analyzed. The results indicate that these cells are capable of repairing all of these structures, although with different efficiencies. Repair of single-stranded gaps and free ends, which occurs most efficiently, is always associated with acquisition of information from the uncut strand (unidirectional reapir). Regions containing single loops or twin loops were repaired at similar efficiencies. In these cases each of the two strands was capable of acting as the template for repair (bidirectional repair). At sites containing twin or substitution loops, the larger of the loops was removed twice as efficiently as the smaller loop. DNA sequencing of the repaired regions indicated that the repair is precise. The data also suggest that markers separated by only 58 nucleotides do nor always segregate together indicating that repair tracts may be relatively short.

Original languageEnglish (US)
Pages (from-to)181-188
Number of pages8
JournalMutation Research - Fundamental and Molecular Mechanisms of Mutagenesis
Issue number1
StatePublished - Mar 1989

Bibliographical note

Funding Information:
We thank Ms. L. Chekuri and S. Frey for technical support. Ms. V. Cummins typed the manuscript. This work is supported by grants from the NIH (GM 33943, GM 36565) and by the March of Dimes Birth Defects Foundation (I-806). C.C. is the recipient of an NRSA award (GMl1893-02).


  • DNA gapsl
  • DNA repair
  • Escherichia coli
  • Heteroduplex repair
  • single-stranded


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