IHF modulation of Tn10 transposition: sensory transduction of supercoiling status via a proposed protein/DNA molecular spring.
Architectural protein IHF modulates Tn10 transposition in vitro. IHF stimulates transposon excision. Also, separately, IHF forces transposon end/target DNA interactions into a constrained pathway, "channeling," that yields only unknotted intratransposon inversion circles. Negative supercoiling influences both effects, differently. We infer that IHF is an architectural catalyst: it promotes initial transpososome assembly and is then ejected from the transpososome. IHF then rebinds, altering transpososome conformation to promote channeling. We also infer that the developing transpososome is a molecular spring: DNA provides basic elasticity; a conformational change in transposase provides force; and IHF and/or supercoiling provide conformational inputs. In vivo, IHF is a sensory transducer of chromosomal supercoiling status: with supercoiling absent, IHF is "supercoiling relief factor"; with supercoiling present, stimulation and channeling comprise a homeostatic pair such that modest changes in chromosome condition strongly influence transpositional outcome.
Chalmers
R
R
Department of Molecular and Cellular Biology, Harvard University, Cambridge, Massachusetts 02138, USA.
Guhathakurta
A
A
Benjamin
H
H
Kleckner
N
N
D001426:Bacterial Proteins / Q000378:metabolism*; D004261:DNA Replication; D004251:DNA Transposable Elements / Q000235:genetics*; D004269:DNA, Bacterial / Q000378:metabolism; D004278:DNA, Superhelical / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics*; D034982:Integration Host Factors; D008957:Models, Genetic; D008961:Models, Structural; D011485:Protein Binding; D011995:Recombination, Genetic; D015398:Signal Transduction
D001426:Bacterial Proteins; D004251:DNA Transposable Elements; D004269:DNA, Bacterial; D004278:DNA, Superhelical; D004268:DNA-Binding Proteins; D034982:Integration Host Factors; C040330:histone-like protein HU, bacteria