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Spontaneous deletion of citrate-utilizing ability promoted by insertion sequences
Journal of Bacteriology
|November 1, 1984
Summary
The citrate utilization (Cit+) transposon Tn3411, flanked by IS3411 elements, undergoes frequent deletions via intramolecular recombination. These IS3411 elements facilitate transposition, with inverse transposition being more efficient than direct transposition.
Area of Science:
- Molecular Biology
- Genetics
- Microbiology
Background:
- The citrate utilization (Cit+) transposon Tn3411 is characterized by flanking directly repeated sequences, IS3411L and IS3411R.
- Plasmid pBR322 carrying Tn3411 is prone to generating Cit- deletion mutants through intramolecular recombination between the IS3411 copies.
Purpose of the Study:
- To investigate the functional role of the flanking IS3411 elements in Tn3411 transposition.
- To analyze the mechanisms and frequencies of direct and inverse transposition mediated by Tn3411.
- To examine the role of homologous recombination in spontaneous deletions within Tn3411.
Main Methods:
- Restriction enzyme analysis and electron microscopy were used to characterize Tn3411 and its flanking sequences.
- Transposition assays were performed to evaluate direct and inverse transposition events.
- Experiments were conducted in recA+ and recA- hosts to assess the role of recombination in deletions.
Main Results:
- The IS3411 elements flanking Tn3411 are functional insertion sequences capable of mediating both direct and inverse transposition.
- Inverse transposition of Tn3411 to the F-plasmid derivative pED100 was more efficient than direct transposition of the Cit+ determinant.
- Transposition of marked IS3411 elements occurred at a higher frequency than cointegrate formation, suggesting replicon fusions are not essential intermediates.
- Spontaneous deletions, particularly those promoted by homologous recombination between IS3411 elements, occurred frequently in recA hosts.
Conclusions:
- The IS3411 elements are key determinants of Tn3411's transpositional activity and recombination potential.
- Differential transposability of IS3411L and IS3411R may influence the efficiency of various transposition pathways.
- Homologous recombination between IS3411 elements plays a significant role in generating spontaneous deletions within Tn3411, especially in recA-deficient backgrounds.