Figure 3.

ago1 null mutants fail to activate the S-M DNA replication checkpoint. (A) FY254 and Δago1 strains transformed with vector (pREP3X), pREP3X +ago1⁺, or pREP3X +hAgo2 were streaked onto leucine-deficient EMM plates containing 10 mM HU and incubated for 3 d at 30°C. Viability of the Δago1 strain containing pREP3X was confirmed by growth on EMM lacking both leucine and HU (our unpublished data). (B) Immunoblot analyses of total and phosphorylated Cdc2 (Cdc2-P) from FY254 and Δago1 strains in unsynchronized cultures (US), during HU treatment (+10 mM HU) and after removal of HU (Wash Out). Mean septation indices (determined from four independent experiments) are shown for each time point (bar graph).