Changes in the ubiquitin-proteasome system during evolution.

<p>(A) Inhibition of the ancestor and the evolved lines by cycloheximide. To test the sensitivity of the populations to protein synthesis inhibitor, the growth medium was supplemented with sublethal dosage of cycloheximide (0.06 μg/ml). Inhibition rates were calculated by comparing growth rates in drug-containing and drug-free media, and were normalized to that of the wild-type control. The bars indicate mean ± 95% confidence interval. Mann-Whitney U test was used to assess difference in fitness between ancestor and evolved lines. */**/*** indicates <i>p</i>-value < 0.05/0.01/0.001, respectively. To ensure that changes in inhibition rates do not simply reflect the direct effects of mistranslation, tRNA_CAG^Ser was swapped for the corresponding empty vector in the ancestor and the evolved lines. (B) Changes in proteasome activity during evolution. Proteasome activities were normalized to the activity measured in wild-type control carrying no tRNA_CAG^Ser. The bars indicate mean ± standard error. Two-sample <i>t</i> test was used to assess the difference in proteasome activity between the ancestor and the evolved lines. */**/*** indicates <i>p</i>-value < 0.05/0.01/0.001, respectively.