Journal:

Article Title: Single-Strand-Specific Exonucleases Prevent Frameshift Mutagenesis by Suppressing SOS Induction and the Action of DinB/DNA Polymerase IV in Growing Cells

doi: 10.1128/JB.188.7.2336-2342.2006

Figure Lengend Snippet: (A) Increased spontaneous frameshift mutation in ExoI− ExoVII− cells requires PolIV, RecA, and an inducible LexA. The values represent averages (±standard errors of the mean) of increases in the mutation rate relative to Exo+ within each experiment (Tables ​(Tables22 and ​and3).3). The dinB, recA, and lexA(Ind−) strains all displayed significantly lower mutation rates than xonA xseA (P < 0.04; single-factor analysis of variance and Tukey test calculated with SigmaStat 3.1 [Systat Software, Inc., Point Richmond, CA]). Also, the dinB, recA, and lexA(Ind−) strains were not significantly different from Exo+ (see Tables ​Tables22 and ​and33 for P values). (B to E) Increased green fluorescence of ExoI− ExoVII− cells carrying a chromosomal SOS-GFP reporter construct indicates chronic low-level SOS induction. All cells carry a chromosomal fusion of the SOS-controlled sulA promoter to a gfp gene (15, 25). (B and D) Bright-field and (C and E) fluorescence images of isogenic “wild-type” (SMR6039) and ExoI− ExoVII− (SMR9163) cells, respectively.

Article Snippet: The mutation rates in single-strand-exonuclease-proficient (Exo + ) cells were 9.3 (±2) × 10 −10 and 2.6 (±0.2) × 10 −9 mutations per cell per generation for the episomal lac and chromosomal tet alleles, respectively (Tables and ). table ft1 table-wrap mode="anchored" t5 TABLE 2. caption a7 Relevant genotype Exp no. Mutation rate (mutations/cell/generation) Mean mutation rate (± SEM) (mutations/cell/generation) P value a Difference ( n -fold) from Exo + control strain Mean difference ( n -fold) (± SEM) Exo + 1 10 × 10 −10 9.3 (±2) × 10 −10 <0.001 1 2 9.9 × 10 −10 3 11 × 10 −10 4 12 × 10 −10 5 11 × 10 −10 6 3.3 × 10 −10 7 21 × 10 −10 8 8.4 × 10 −10 9 7.1 × 10 −10 10 2.6 × 10 −10 11 5.6 × 10 −10 Δ xonA Δ xseA 1 72 × 10 −10 76 (±11) × 10 −10 N/A 7.2 10 ± 2 2 79 × 10 −10 8.0 3 39 × 10 −10 3.5 4 53 × 10 −10 4.4 5 77 × 10 −10 7.0 6 64 × 10 −10 19 7 180 × 10 −10 8.6 8 68 × 10 −10 8.1 9 93 × 10 −10 13 10 49 × 10 −10 19 11 68 × 10 −10 12 Δ xonA Δ xseA dinB 1 20 × 10 −10 33 (±7) × 10 −10 0.007 2.0 3.7 ± 0.7 2 35 × 10 −10 3.5 3 63 × 10 −10 5.7 4 17 × 10 −10 1.4 5 42 × 10 −10 3.8 6 18 × 10 −10 5.5 Δ xonA Δ xseA recA 1 20 × 10 −10 21 (±8) × 10 −10 0.008 2.0 1.4 ± 0.4 3 8.0 × 10 −10 0.73 7 34 × 10 −10 1.6 Δ xonA Δ xseA lexA (Ind − ) 9 25 × 10 −10 20 (±6) × 10 −10 0.007 3.5 3.8 ± 0.6 10 7.7 × 10 −10 3.0 11 27 × 10 −10 4.8 Open in a separate window a P values are for the difference from the Δ xonA Δ xseA strain for overall averaged mutation rates and were calculated by single-factor analysis of variance and the Tukey test with SigmaStat 3.1 (Systat Software, Inc., Point Richmond, CA).

Techniques: Mutagenesis, Software, Fluorescence, Construct