Insertion site preference of Mu, Tn5, and Tn7 transposons

BACKGROUND: Transposons, segments of DNA that can mobilize to other locations in a genome, are often used for insertion mutagenesis or to generate priming sites for sequencing of large DNA molecules. For both of these uses, a transposon with minimal insertion bias is desired to allow complete coverage with minimal oversampling. FINDINGS: Three transposons, Mu, Tn5, and Tn7, were used to generate insertions in the same set of fosmids containing Candida glabrata genomic DNA. Tn7 demonstrates markedly less insertion bias than either Mu or Tn5, with both Mu and Tn5 biased toward sequences containing guanosine (G) and cytidine (C). This preference of Mu and Tn5 yields less uniform spacing of insertions than for Tn7, in the adenosine (A) and thymidine (T) rich genome of C. glabrata (39% GC). CONCLUSIONS: In light of its more uniform distribution of insertions, Tn7 should be considered for applications in which insertion bias is deleterious.