Figure 4.

In the absence of UvrD, blocked replication forks persist leading to the accumulation of higher-order recombination intermediates in a manner similar to uvrA mutants. (a) Diagram of structural intermediates observed in the presence or absence of UV-induced damage. (b) Cells containing the pBR322 plasmid were UV-irradiated with 50 J/m². At the times indicated, genomic DNA was purified, digested with PvuII, and the structural intermediates were examined by two-dimensional agarose gel analysis. Gels shown are representative of at least two independent experiments. (c) The percentage of UV-induced intermediates relative to nonreplicating plasmids over time is plotted. Percentages were quantified as the ratio of radioactivity in either the cone region or the high-order intermediate region over the amount of radioactivity in the nonreplicating region.