Figure 6.

Detection of SSBs in the GAL2 UAS region. (A) Detection of SSBs by S1 nuclease. Plugs containing genomic DNA from wild-type cells were directly equilibrated in restriction digestion buffer and treated with NcoI and XbaI. Genomic DNA recovered from the melted plugs was then incubated in the presence (lanes designated +) or absence (lanes designated −) of S1 nuclease. Numbers above the panels are culture time (hours) in SPM. The diagram is labeled as for Figure 5. (B) Schematic diagram of SSB detection in rad50S strains using denaturing polyacrylamide gel. Nt.AlwI introduces an SSB into specific sequences of DNA (5′-GGATCNNNN/N-3′). The GAL2 promoter has the sequence only on the + strand. Probes A and B were labeled by multiple round primer extension in the presence of radio-labeled dCTP. (C) and (D) Detection of SSBs on the −/+ strand by using strand-specific probes. All strains are homozygous for the rad50S allele. After genomic DNA was prepared from the meiotic cells at the indicated times (hours), it was treated with AccI and BspHI. The right two lanes in each panel contain 5% DNA fragments, which were further digested with HhaI or Nt.AlwI. Strains used were YHS363, YHS397, YHS427 and YHS514.