General features and properties of insertion sequence elements

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Impinging transcription

Many ISs have evolved mechanisms which attenuate their activation by impinging transcription following insertion into active host genes. This was originally observed in the case of IS1 (Machida, et al., 1982)(Chandler & Galas, 1983), for bacteriophage Mu (Goosen & van de Putte, 1986) and IS50 (see (Galas & Chandler, 1989)). To our knowledge other elements have not been examined.

This effect may be the result of disrupting complexes between Tpase and cognate DNA ends and could reflect either inhibition of transposase binding or disruption of extant transposase-end complexes.

In the case of bacteriophage Mu, transcription originating from within the element and impinging on the left end has also been shown to reduce activity (Goosen & van de Putte, 1986). It is possible that transcription disrupts the formation of intermediates including transposase and one or both Mu ends which lead to stable transposition complexes.

    References :
  • Chandler M & Galas DJ (1983) Cointegrate formation mediated by Tn9. II. Activity of IS1 is modulated by external DNA sequences. J Mol Biol 170: 61-91.
  • Galas DJ & Chandler M (1989) Bacterial insertion sequences. Mobile DNA,(Berg D & Howe M, eds.), pp. 109-162. American Society for Microbiology, Washington D.C.
  • Goosen N & van de Putte P (1986) Role of ner protein in bacteriophage Mu transposition. J Bacteriol. 167: 503-507.
  • Machida Y, Machida C, Ohtsubo H & Ohtsubo E (1982) Factors determining frequency of plasmid cointegration mediated by insertion sequence IS1. Proc Natl Acad Sci U S A 79: 277-281.