General features and properties of insertion sequence elements

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Terminal inverted repeats

With several notable exceptions (the IS91, IS110 and IS200/IS605 families; Table 1) the majority of ISs exhibit short terminal IR of between 10 and 40 bp. In those cases examined experimentally, the IRs can be divided into two functional domains (Fig 1.26.1). Domain "b" includes the two or three terminal base pairs (Fig 1.26.1), and is involved in the cleavages and strand transfer reactions leading to transposition of the element. Domain "a" is positioned within the IR and is involved in Tpase binding (Derbyshire & Grindley, 1996), (Derbyshire, et al., 1990), (Huisman, et al., 1989), (Johnson & Reznikoff, 1983), (Makris, et al., 1988), (Zerbib, et al., 1990), (Normand, et al., 2001). A similar organisation has also been proposed for the transposon Tn3(Ichikawa, et al., 1990) and for the related gd transposon (May & Grindley, 1995). The simple single terminal Tpase binding sites of ISs are to be contrasted with the multiple and asymmetric protein binding sites observed in the case of bacteriophage Mu (Craigie, et al., 1984) and transposons Tn7 (Craig, 1996), and probably Tn552 (Rowland & Dyke, 1990),(Rowland, et al., 1995). Multiple protein binding sites are also a characteristic of the complex En/Spm and Ac elements of maize (see(Gierl, 1996), (Kunze, 1996) (Fig 1.26.2). It is worth noting that members of the IS21 family also carry multiple repeated sequences at both ends which may also represent Tpase binding sites (Berger, et al., 2001), (Mahillon & Chandler, 1998).By accommodating different binding patterns at each end, such an arrangement can provide a functional distinction between the ends either in the assembly or in the activity of the synaptic complex. In addition, indigenous IS promoters are often located partially within the IR sequence upstream of the Tpase gene, by convention IRL. This arrangement may provide a mechanism for autoregulation of Tpase synthesis by Tpase binding. Binding sites for host specified proteins are also often found within or close to the terminal IRs and these proteins may play a role in modulating transposition activity or Tpase expression.

    References :
  • Berger N, Heller AE, Stormann KD & Pfaff E (2001) Characterization of chimeric enzymes between caprine arthritis- encephalitis virus, maedi-visna virus and human immunodeficiency virus type 1 integrases expressed in Escherichia coli. J.Gen.Virol. 82: 139-148.
  • Craig NL (1996) Transposon Tn7. Curr.Top.Microbiol.Immunol. 204: 27-48.
  • Craigie R, Mizuuchi M & Mizuuchi K (1984) Site-specific recognition of the bacteriophage Mu ends by the Mu A protein. Cell 39: 387-394.
  • Derbyshire KM & Grindley ND (1996) Cis preference of the IS903 transposase is mediated by a combination of transposase instability and inefficient translation. Mol Microbiol 21: 1261-1272.
  • Derbyshire KM, Kramer M & Grindley ND (1990) Role of instability in the cis action of the insertion sequence IS903 transposase. Proc Natl Acad Sci U S A 87: 4048-4052.
  • Gierl A (1996) The En/Spm transposable element of maize. Curr.Top.Microbiol.Immunol. 204: 145-159.
  • Huisman O, Errada PR, Signon L & Kleckner N (1989) Mutational analysis of IS10's outside end. Embo J 8: 2101-2109.
  • Ichikawa H, Ikeda K, Amemura J & Ohtsubo E (1990) Two domains in the terminal inverted-repeat sequence of transposon Tn3 Gene 86: 11-17.
  • Johnson RC & Reznikoff WS (1983) DNA sequences at the ends of transposon Tn5 required for transposition. Nature 304: 280-282.
  • Kunze R (1996) The maize transposable element activator (Ac). Curr.Top.Microbiol.Immunol. 204: 161-194.
  • Mahillon J & Chandler M (1998) Insertion sequences. Microbiol Mol Biol Rev 62: 725-774.
  • Makris JC, Nordmann PL & Reznikoff WS (1988) Mutational analysis of insertion sequence 50 (IS50) and transposon 5 (Tn5) ends. Proc.Natl.Acad.Sci.U.S.A. 85: 2224-2228.
  • May EW & Grindley ND (1995) A functional analysis of the inverted repeat of the gamma delta transposable element. J Mol.Biol. 247: 578-587.
  • Normand C, Duval-Valentin G, Haren L & Chandler M (2001) The terminal inverted repeats of IS911: requirements for synaptic complex assembly and activity. J Mol Biol 308: 853-871.
  • Rowland SJ & Dyke KG (1990) Tn552, a novel transposable element from Staphylococcus aureus. Mol.Microbiol. 4: 961-975.
  • Rowland SJ, Sherratt DJ, Stark WM & Boocock MR (1995) Tn552 transposase purification and in vitro activities. EMBO J 14: 196-205.
  • Zerbib D, Prentki P, Gamas P, Freund E, Galas DJ & Chandler M (1990) Functional organization of the ends of IS1: specific binding site for an IS 1-encoded protein. Mol Microbiol 4: 1477-1486.