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
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
- 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,
- Goosen N & van de Putte P (1986) Role of ner
protein in bacteriophage Mu transposition. J
Bacteriol. 167: 503-507.
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: