Alternative interactions between the Tn7 transposase and the Tn7 target DNA binding protein regulate target immunity and transposition.
The Tn7 transposon avoids inserting into a target DNA that contains a pre-existing copy of Tn7. This phenomenon, known as 'target immunity', is established when TnsB, a Tn7 transposase subunit, binds to Tn7 sequences in the target DNA and mediates displacement of TnsC, a critical transposase activator, from the DNA. Paradoxically, TnsB-TnsC interactions are also required to promote transposon insertion. We have probed Tn7 target immunity by isolating TnsB mutants that mediate more frequent insertions into a potentially immune target DNA because they fail to provoke dissociation of TnsC from the DNA. We show that a single region of TnsB mediates the TnsB-TnsC interaction that underlies both target immunity and transposition, but that TnsA, the other transposase subunit, channels the TnsB-TnsC interaction toward transposition.
Howard Hughes Medical Institute, Department of Molecular Biology and Genetics, Johns Hopkins School of Medicine, Baltimore, MD 21205, USA.
Zachary
Z
Skelding
Jennie
J
Queen-Baker
Nancy L
NL
Craig
D000595:Amino Acid Sequence; D010583:Bacteriophage mu / Q000235:genetics / Q000378:metabolism; D004251:DNA Transposable Elements / Q000235:genetics*; D004269:DNA, Bacterial / Q000235:genetics / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D009154:Mutation; D019895:Transposases / Q000235:genetics / Q000378:metabolism*
D004251:DNA Transposable Elements; D004269:DNA, Bacterial; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; C098908:TnsA protein, E coli; C069633:TnsB protein, E coli; C074940:TnsC protein, E coli; D019895:Transposases