Fig 2.
UV-arrested replication forks are processed normally in cells lacking priB, priC, or rep. (A) The predicted migration pattern of PvuII-digested pBR322 plasmid observed by two-dimensional agarose gel analysis and subsequent visualization with 32P-labeled pBR322 is diagrammed. Nonreplicating plasmids run as a linear 4.4-kb fragment. Replicating plasmids form Y-shaped structures that migrate slower than nonreplicating DNA, forming an arc that extends above the linear region. Following UV irradiation, double-Y- or X-shaped intermediates are observed that migrate in the cone region behind the arc of Y-shaped molecules. (B) Two-dimensional agarose gels from wild-type, recF, priB302, priC, and rep cultures containing pBR322 at the indicated times following UV irradiation.