TABLE 4

Enhanced frameshift mutation rate of exonuclease mutants

Rate × 107
StrainDescription+1 Frameshifts-1 Frameshifts
BT199Exo+8.53.7
STL2694ExoI105.2
STL2347ExoVII5527
STL2758ExoI ExoVII27042
STL2971ExoI ExoVII RecJ30087
STL3240MutS5031
STL3187MutS ExoI ExoVII3242
  • Frameshift assay plasmids pXVII and PXIX (Hoffman et al. 1996) were transformed into the strains indicated above. +1 and −1 frameshift formation was assayed by plating to Tc-medium. Twenty μg/ml ICR-191 was added to cultures during preplating growth. Mutation rates were determined by the method of the median as described in materials and methods. Reported rates for each strain are averages of two sets of eight independent cultures.