Genetic evidence against intramolecular rejoining of the donor DNA molecule following IS10 transposition.
Tn10 and IS10 transpose by a nonreplicative mechanism in which the transposon is excised from the donor molecule and integrated into a target DNA site, leaving behind a break at the original donor site. The fate of this broken donor DNA molecule is not known. We describe here two experiments that address this issue. One experiment demonstrates that a polar IS10 element gives rise to polarity-relief revertants at less than 1% the frequency of transposition of the same element in the same culture. In a second experiment, transpositions of an IS10 element from one site in the bacterial genome to another are selected and the resulting isolates examined for alterations at the donor site; none of 1088 such isolates exhibited a detectable change at the donor locus. These results are compatible with two possible fates of the transposon donor molecule: degradation ("donor suicide"), or restoration of the original information at the donor site by a recombinational repair mechanism analogous to double-strand break repair. These results argue against the possibility that the donor molecule gap is simply resealed by intramolecular rejoining.
Bender
J
J
Department of Biochemistry and Molecular Biology, Harvard University, Cambridge, Massachusetts 02138.
Kuo
J
J
Kleckner
N
N
D010582:Bacteriophage lambda / Q000235:genetics; D002876:Chromosomes, Bacterial / Q000502:physiology; D003433:Crosses, Genetic; D004260:DNA Repair; D004251:DNA Transposable Elements / Q000235:genetics*; D004352:Drug Resistance, Microbial; D004926:Escherichia coli / Q000235:genetics; D005785:Gene Conversion; D005814:Genes, Viral; D008957:Models, Genetic; D009876:Operon / Q000235:genetics; D011995:Recombination, Genetic; D012475:Salmonella / Q000235:genetics; D012483:Salmonella Phages / Q000235:genetics
D004251:DNA Transposable Elements