FIG. 4.

A change in superhelicity confirms the loss of nucleosomes from the plasmid upon induction. (A) Genomic DNA from strain YS1801 (wt) and YS3101 (pho80) both carrying the plasmid pTAP5CΔTATA was analyzed in an agarose gel containing 33 μM chloroquine. Three independent but parallel cultures were grown logarithmically in high-phosphate media for each strain. The arrowheads mark each maximum of the Gaussian distribution as averaged over the three lanes for each strain (closed arrowhead, YS1801; open arrowhead, YS3101). The difference in linking number between the repressed and induced states was 2.5 ± 0.4. Lanes 1 and 8 contain linearized plasmid as a marker and the position of the nicked circular and the linear form of the plasmid is indicated on the right side of the gel. (B) Trace profiles of lane 3 (top) and lane 5 (bottom) are shown and the respective maxima of the Gaussian fit indicated by arrowheads. The position of the nicked circular form was used as the origin for the trace profile.