Sequestration of translation initiation signals

One such mechanism observed with IS10 and IS50, and potentially present in several other ISs, is the sequestering of translation initiation signals in an RNA secondary structure (Fig 1.32.1). These ISs carry inverted repeat sequences located close to the left end which include the ribosome binding site or translation initiation codon for the Tpase gene. Transcripts from the resident Tpase promoter include only the distal repeat unit which is unable to form the secondary structure, while transcripts from neighboring DNA include both repeats and would generate secondary structures in the mRNA which would sequester translation initiation signals (Davis, et al., 1985), (Krebs & Reznikoff, 1986). This has been demonstrated experimentally for IS10 and IS50 but several additional insertion sequences carry such potential structures and might be expected to exhibit a similar mechanism (see (Rezsohazy, et al., 1993).

References :

• Davis MA, Simons RW & Kleckner N (1985) Tn10 protects itself at two levels from fortuitous activation by external promoters. Cell 43: 379-387.
• Krebs MP & Reznikoff WS (1986) Transcriptional and translational initiation sites of IS50. Control of transposase and inhibitor expression. J Mol.Biol. 192: 781-791.
• Rezsohazy R, Hallet B, Delcour J & Mahillon J (1993) The IS4 family of insertion sequences: evidence for a conserved transposase motif. Mol Microbiol 9: 1283-1295.