FIG. 5.

(A) Cln2 expression does not result in Clb2 accumulation. clb3Δ clb4Δ clb5Δ GAL-CLB5 (US2417) cells were arrested in G₁ with α factor in YEP+Raff. The culture was filtered, and cells were resuspended in YEP+Raff for 2 h. Galactose (2%) was then added to induce the synthesis of Clb5 for 2 h. In parallel, clb3Δ clb4Δ clb5Δ GAL-CLB5 MET3-HA₃-CLN2 (US2439) cells, synchronized in G₁ by α-factor treatment in YEP+Glu+Met, were filtered and resuspended in YEP+Glu+Met for 2 h. Cells were then transferred to −Met+Glu medium to induce the synthesis of HA₃-Cln2 for 2 h. Samples were analyzed for Clb2 and Cdc28 protein levels and CLB5, CLB2, and CLN2 RNA levels. (B) Overexpression of Cln2 is unable to restore viability in clb3Δ clb4Δ clb5Δ cells. clb3Δ clb4Δ clb5Δ GAL-CLB5 cells were plated on either glucose (upper right) or galactose (upper left) plates, whereas clb3Δ clb4Δ clb5Δ GAL-CLB5 MET3-HA₃-CLN2 cells were plated on −Met+Glu medium. Plates were photographed after 3 days at 24°C.