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Transposon Tn7. cis-Acting sequences in transposition and transposition immunity
L K Arciszewska1, D Drake, N L Craig
1Department of Microbiology and Immunology, University of California, San Francisco 94143.
Journal of Molecular Biology
|May 5, 1989
Summary
The bacterial transposon Tn7 uses specific DNA sequences at its ends for transposition to both targeted and random sites. These sequences, Tn7L and Tn7R, are distinct and their presence can inhibit further Tn7 insertions.
Area of Science:
- Molecular Biology
- Genetics
- Microbiology
Background:
- Bacterial transposons are mobile genetic elements that can move within a genome.
- Transposon Tn7 exhibits distinct transposition behaviors, including high-frequency targeted and low-frequency random integration.
- Understanding the regulatory sequences governing transposition is crucial for comprehending genome dynamics.
Purpose of the Study:
- To identify and characterize the cis-acting DNA sequences at the termini of bacterial transposon Tn7 required for transposition.
- To investigate the functional distinction between the left (Tn7L) and right (Tn7R) ends of Tn7.
- To determine the effect of Tn7's cis-acting sequences on subsequent transposition events.
Main Methods:
- Analysis of cis-acting sequences at the termini of transposon Tn7.
- Functional characterization of Tn7 ends using mini-Tn7 elements.
- Assessment of transposition inhibition by Tn7 cis-acting sequences in target replicons.
Main Results:
- Specific cis-acting sequences at the Tn7 left (approx. 150 bp) and right (approx. 70 bp) ends are essential for transposition.
- The Tn7 ends are functionally distinct, with Tn7R being active and Tn7L inactive in a mini-Tn7 element with two identical ends.
- The presence of Tn7's cis-acting transposition sequences inhibits subsequent Tn7 insertions into target sites, with Tn7R being necessary and sufficient for this inhibition.
Conclusions:
- The same cis-acting sequences at the Tn7 termini mediate both high-frequency targeted and low-frequency random transposition.
- Functional asymmetry exists between the Tn7L and Tn7R ends.
- Tn7 transposition exhibits a feedback inhibition mechanism mediated by its own cis-acting sequences.