Factors Affecting Transposition Activity of IS50 and Tn5 Ends

Gene. 1989;76(2):207-13. doi: 10.1016/0378-1119(89)90161-3.


The partially matched I and O ends of IS50 (the insertion sequence of the transposon Tn5) are needed for transposition, probably as the sites upon which the cis-acting transposase and host proteins act. To better understand how transposition is regulated we made a series of IS50-related elements in which the positions of the ends and of the transposase gene were varied systematically. Assays of these elements showed that the I and O ends differ inherently in transposition activity. Other workers showed that methylation, at DNA N6-adenine methyltransferase (Dam) recognition sites within the I end and the transposase tnp gene promoter, inhibits transposase synthesis and also I end activity. We show that the effect of Dammediated methylation on an I end depends on the end's orientation relative to the tnp gene. Further, in dam+ cells oriented like -tnp----in relation to the first and second ends) are (O, I) greater than (O, O) greater than or equal to (I, O) greater than (I, I). In dam- cells the relative activities are (O, I) = (I, O) = (I, I) greater than (O, O). Our results are consistent with a model orginally developed for IS10, in which hemi-methylation resulting from passage of a replication fork regulates transposition.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Bacteriophage lambda / genetics
  • Base Sequence
  • DNA Transposable Elements*
  • DNA, Recombinant
  • Methylation
  • Methyltransferases / metabolism
  • Nucleotidyltransferases / genetics
  • Plasmids
  • Site-Specific DNA-Methyltransferase (Adenine-Specific)*
  • Transcription, Genetic
  • Transduction, Genetic
  • Transposases


  • DNA Transposable Elements
  • DNA, Recombinant
  • Methyltransferases
  • Dam methyltransferase
  • Site-Specific DNA-Methyltransferase (Adenine-Specific)
  • Nucleotidyltransferases
  • Transposases