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Cell. 1998 May 29;93(5):897-908.

IHF modulation of Tn10 transposition: sensory transduction of supercoiling status via a proposed protein/DNA molecular spring.

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Department of Molecular and Cellular Biology, Harvard University, Cambridge, Massachusetts 02138, USA.


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.

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