Abstract
The role of T7-induced exonuclease (gene 6) in molecular recombination was studied by examining the fate of parental DNA during parental-to-progeny recombination. The method used was to compare infections with T7(+), T7am-6-233 (am gene 6), or T7ts6-136 (ts gene 6) under permissive and nonpermissive conditions. CsCl density gradient analysis of replicative DNA indicated that T7 exonuclease is necessary for recombination to occur, i.e., in the absence of the exonuclease the parental DNA replicated continuously as a hybrid molecule and did not recombine. Further studies under conditions where replicative DNA was denatured and analyzed by CsCl density gradient centrifugation indicated that the exonuclease is also needed for a limited amount of covalent repair of recombinants. A repair function for the T7-induced exonuclease is also suggested by results obtained from alkaline sucrose gradient analysis of replicative DNA. Under conditions nonpermissive for the exonuclease, discontinuities in the DNA accumulated during infection by T7am6-233 or by T7ts6-136.
MeSH Terms
Bromodeoxyuridine/metabolism
Centrifugation, Density Gradient
Chloramphenicol/pharmacology
Coliphages/enzymology
DNA Repair
DNA Replication
DNA Viruses
DNA, Viral/biosynthesis
Escherichia coli
Exonucleases/metabolism
Genes
Mutation
Phosphates/metabolism
Phosphorus Radioisotopes
Recombination, Genetic
Temperature
Thymidine/metabolism
Tritium
Chemicals
DNA, Viral
Phosphates
Phosphorus Radioisotopes
Tritium
Chloramphenicol
Exonucleases
Bromodeoxyuridine
Thymidine
Authors & Affiliations
2 authors, click to expand affiliations / ORCID
Lee M
Miller R C
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