Figure 3.—

Analysis of cell cycle defects in srp1 mutants. (A) Analysis of cell growth on hydroxyurea and benomyl plates. To determine whether any of the srp1 mutant alleles show hypersensitivity to growth on plates containing hydroxyurea or benomyl, cultures were grown to saturation at the permissive temperature and then serially diluted and spotted on control YEPD plates, YEPD containing 100 mm hydroxyurea, or YEPD plates containing 10 mg/ml benomyl. Plates were incubated at the permissive temperature for 3–7 days. (B) Analysis of cell cycle progression in unsynchronized cells. Wild-type (SRP1) and mutant (srp1-31, srp1-55, and srp1-E402Q) cells were grown to early mid-log phase at the permissive temperature and then shifted to the nonpermissive temperature (37° for srp1-31 and srp1-E402Q cells and 18° for srp1-55 cells). Samples were collected every 30 min for 6 hr for flow cytometry to analyze DNA content. The positions of unreplicated DNA (1N) and replicated DNA (2N) are indicated below the graphs.