Post-replication repair mutants are insensitive to chromium.

Competitive growth assays were performed with the indicated concentrations of chromate, CPT, 4-NQO, and cisplatin. Cells lacking the PRR proteins Rhp18/RAD18 or Ubc13 are sensitive to 4-NQO and cisplatin but not chromate or CPT. Elimination or Rhp14/XPA further increases 4-NQO and cisplatin sensitivities in cells lacking Ubc13. Cells lacking Hrq1/RECQL4 DNA helicase are only sensitive to cisplatin, whilst even co-elimination of Hrq1 and Ubc13 fails to cause any chromate or CPT sensitivity. Bars indicate standard deviation from 3 independent experiments. Statistically significant differences as determined by a two-tailed Student’s t-test are indicated.