Sequence-induced DNA curvature at the bacteriophage λ origin of replication

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Abstract
DNA replication in bacteriophage λ begins at a unique origin between residues 39,000 and 39,200 of the λ genome1. This segment of DNA serves a dual function since it also lies within the coding sequence of the λ replication initiator protein O which binds origin DNA2,3. The λ origin sequence contains four 19-base-pair (bp) segments (iterons) which have dyad symmetry, followed by a 40-bp A + T-rich zone of highly asymmetrical base composition2. It was noted earlier4 that λ origin DNA exhibits an anomalous electrophoretic mobility on gels; that is, the length of DNA as determined by DNA sequencing is ∼20% less than is predicted from electrophoretic mobility. Recent studies of kinetoplast minicircle DNA (K-DNA) from the protozoan Leishmania tarentolae have led to the proposal that sequence-induced DNA curvature could account for such electrophoretic anomalies by alteration of the shape of the DNA molecule5–8. We now present evidence that the λ origin contains a static curve.

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