FIG. 7.

The varying mutation rate across Chromosome VI depends on translesion synthesis. To test the hypothesis that the correlation between replication time and mutation rate is due to the temporal separation of template switching and translesion synthesis, REV1 (which encodes a translesion polymerase essential for translesion synthesis) was deleted in four strains that show variation in mutation rate and replication timing. Strains GL·3, GL·15, GL·24, and GL·37 (green arrows in fig. 6A) are replicated at 44.5, 43.8, 26.5, and 13.7 min, respectively. Disruption of translesion synthesis results in a strong reduction in the mutation rate in the late-replicating/high mutation rate region. For early-replicating regions with low mutation rates, there is no significant effect of REV1 deletion.