Host Functions Required for Transposition of Tn5 from λ b221 cI857 rex::Tn5
By assaying transposition of Tn5 from λ b221 cI857 rex: :Tn5 (Berg,1977)(abbreviated as λ::Tn5) in PolA-proficient and deficient cells, both DNA polymerase and 5′ to 3′ exonuclease activities of DNA polymerase I of Escherichia coli K12 have been shown to be required for transposition of Tn5. Such a requirement could not clearly be observed in three other experiments in which the transposon donor replicon had existed in cells before transposition was assayed presumably because a hypothetical repressor-regulated protein encoded by the transposon itself rather than DNA polymerase I became rate-limiting in the overall transposition process. One polA mutant was found among more than 50 transposition-deficient mutants isolated by the ′ ::Tn5 method. Preliminary experiments also suggested that several host functions related to DNA repair or recombination were involved in determining the frequency of transposition of Tn5.
KeywordsTransposable Element Kanamycin Resistance Exonuclease Activity Conjugative Plasmid polA Mutant
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