The enhanced requirement for Rev1's catalytic activity occurs in the absence of error-free tolerance after 4-NQO damage. (A) The deletion of rad14 does not increase the divergence of the catalytic dead rev1 strain's 4-NQO killing curve from the REV1 strain's curve. Strains are YMEW7 (rev1Δ pRS416), YMEW8 (rev1Δ pRS416-REV1), YMEW20 (rev1Δrad14Δ pRS416), YMEW21 (rev1Δrad14Δ pRS416-REV1), and YMEW22 (rev1Δrad14Δ pRS416-rev1-catalytic dead). (B) The catalytic dead rev1 strain is significantly more sensitive to 4-NQO in the mms2Δ background. Strains are YMEW7 (rev1Δ pRS416), YMEW8 (rev1Δ pRS416-REV1), YMEW17 (rev1Δmms2Δ pRS416), YMEW18 (rev1Δmms2Δ pRS416-REV1), and YMEW19 (rev1Δmms2Δ pRS416-rev1-catalytic dead). The error bars represent one standard deviation of three or more independent cultures.