Extra copies of TEF3 , TEF4 and TEF5 suppress synthetic lethality between sup45-sl23tsand SUP35-C. (A) The multicopy plasmids YEplac195-TEF4 (TEF4↑), YEplac195-SUP45 (SUP45↑), with the TEF4 and SUP45 genes, respectively, or the multicopy empty vector YEplac195 were introduced into the strain 33G-D373-rSL23-r35C with the sup45-sl23tsand SUP35-C alleles, bearing the centromeric plasmid pCM183-SUP45. Obtained transformants were streaked on C-Ura medium containing doxycycline and incubated at 30°C for 2 days. (B) Transformants of the strain 33G-D373-rSL23-r35C containing the pCM183-SUP45 plasmid along with the empty multicopy YEplac181 (M-empty) or centromeric pRS315 (C-empty) vectors were used as negative control. Transformants with the centromeric plasmids pRS315-SUP35C (SUP35-CEN) and pRS315-SUP45 (SUP45-CEN) bearing the SUP35 and SUP45 genes, respectively, represented positive control, since a single copy of either one of these genes abolished synthetic lethality . Growth of the control transformants was compared with that of the transformants bearing one of the multicopy plasmids YEplac181-TEF2 (TEF2↑), YEplac181-TEF4Δi (TEF4-Δi↑), YEplac181-TEF3 (TEF3↑) or YEplac181-TEF5Δi (TEF5-Δi↑). Transformants were grown in liquid C-Leu medium at 30°C and diluted to an OD600 of 1.0. Ten-fold serial dilutions were spotted onto C-Leu medium which contained (Dox+) or did not contain (Dox-) doxycycline and grown at 30°C for 3 days.