Department of Chemistry, Yale University, New Haven, Connecticut 06511.
Nature 368: 163-6 (1994)
Abstract
The bending and flexibility of DNA are important in packaging,
recombination and transcription. Bending decreases electrophoretic
mobility in a manner depending on bend position within a fragment
(circular permutation) and on the distance between bends (phasing
analysis). Bending can also affect DNA ring closure (cyclization). The
lack of a complete theory for the mechanism of gel retardation hampers
measurement of bend magnitudes by electrophoresis, whereas cyclization
is done entirely in solution and is well understood theoretically.
Disagreements between bend angles estimated by the two electrophoretic
assays have been ascribed to DNA flexibility. Here we test this
interpretation using an internal loop as a model flexible locus. Whereas
the circular permutation and helical phasing experiments are only
subtly affected by the loop, DNA cyclization kinetics detects and
quantifies substantial increases in torsional and bending flexibility.
Furthermore, the results support a functional role for the stress of DNA
bending in inducing base-pair opening.
Mesh Headings
Unique Identifier: 94187849
Chemical Identifiers (Names)