Fig. 2

Four additional strains with translation initiation blocks are high-yielding for Fps1. The ribosomal biogenesis deletion mutants, ssf1Δ, nop12Δ, rpl31aΔ and rpl22aΔ have a decrease in the levels of 60S ribosomal subunit [21, 22]. The upper panel shows a representative polysome profile containing halfmers after each monosome and polysome peak for the strain nop12Δ. Halfmers (indicated with arrows) occur when the PIC binds to mRNA in the absence of the 60S subunit; the PIC then scans through the start codon [23]. The monosome/polysome ratio for each strain is tabulated in the lower panel. The four mutant strains were then transformed with the vector pYX222-FPS1-HA₃ and Fps1 yields analysed at A₆₀₀ ~ 1 by immunoblot; values are reported relative to FPS1-HA₃ expressed in wild-type cells. Experiments were performed in biological triplicates; where relevant, the standard error of the mean (SEM) is shown in parentheses