Table 1.
Mutator effects of polAexo and polBex alleles in various strain backgrounds.a
|
lac orientation (strand)c |
lac → lac+ (per 108) | ||||
|---|---|---|---|---|---|
|
lac alleleb |
Pol+ | polAexo | polBex | polAexo polBex | |
| A. mutL+ | |||||
| G·C → A·T | R(lagging) | 2.5 ±0.7 | 2.3 ±0.9 [0.9] | ND | ND |
| L(leading) | 2.1 ±0.8 | 1.8 ±0.8 [0.8] | ND | ND | |
| G·C → T·A | R(lagging) | 0.8 ±0.7 | 3.3 ±1.0 [4.1] | ND | ND |
| L(leading) | 1.8 ±1.0 | 1.8 ±0.9 [1.0] | ND | ND | |
| A·T → T·A | R(lagging) | 0.9 ±0.5 | 1.5 ±0.5 [1.6] | ND | ND |
| L(leading) | 0.6 ±0.5 | 1.6 ±0.5 [2.7] | ND | ND | |
| A·T → G·C | L(lagging) | 0.1 ±0.1 | 0.1 ±0.1 [1.0] | ND | ND |
| R(leading) | 0.1 ±0.2 | 0.1 ±0.1 [1.0] | ND | ND | |
| RifR | 1.2 ±0.9 | 1.8 ±1.3 [1.5] | ND | ND | |
| NalR | 0.2 ±0.2 | 0.2 ±0.3 [1.0] | ND | ND | |
| B. mutL | |||||
| G·C→A·T | R(lagging) | 43 ±11 | 69 ±19 [1.6] | 50 ±24 [1.2] | 79 ±26 [1.8] |
| L(leading) | 150 ±35 | 167 ±26 [1.1] | 200 ±41 [1.3] | 163 ±38 [1.1] | |
| G·C→T·A | R(lagging) | 1.9 ±0.8 | 3.9 ±1.6 [2.1] | 4.5 ±3.2 [2.4] | 6.1 ±1.6 [3.2] |
| L(leading) | 3.8 ±0.7 | 2.6 ±0.8 [0.7] | 3.6 ±1.4 [0.9] | 3.3 ±1.6 [0.9] | |
| A·T→T·A | R(lagging) | 1.0 ±0.7 | 1.7 ±1.0 [1.7] | 1.6 ±0.9 [1.6] | ND |
| L(leading) | 3.0 ±1.3 | 5.5 ±4.0 [1.8] | 2.4 ±1.2 [0.8] | ND | |
| A·T→G·C | L(lagging) | 17 ±3 | 23 ±5 [1.4] | 26 ±12 [1.6] | ND |
| R(leading) | 48 ±10 | 48 ±9 [1.0] | 36 ±22 [0.8] | ND | |
| RifR/108 | 277 ±115 | 244 ±166 [0.9] | 311 ±170 [1.1] | 261 ±74 [0.9] | |
| C. mutL dnaE915 | |||||
| G·C→A·T | R(lagging) | 9.0 ±3.6 | 34 ±31 [3.8] | 63 ±32 [6.4] | 86 ±26 [8.7] |
| L(leading) | 30 ±4 | 29 ±3.0 [1.0] | 67 ±13 [2.2] | 51 ±12 [1.7] | |
| G·C→T·A | R(lagging) | 1.6 ±0.6 | 4.1 ±0.6 [2.6] | 6.0 ±2.0 [3.8] | 8.8 ±2.8 [5.5] |
| L(leading) | 0.7 ±0.3 | 0.7 ±0.3 [1.0] | 2.5 ±0.9 [3.6] | 2.9 ±0.8 [4.1] | |
| A·T→T·A | R(lagging) | 0.5 ±0.6 | 1.7 ±3.4 [3.4] | 3.8 ±1.9 [7.6] | ND |
| L(leading) | 0.3 ±0.4 | 9.5 ±4.4 [32] | 2.2 ±0.7 [7.3] | ND | |
| A·T→G·C | L(lagging) | 7.0 ±1.1 | 18 ±2.4 [2.6] | 35 ±7 [5.0] | ND |
| R(leading) | 5.5 ±2.0 | 8.2 ±3.1 [1.5] | 12 ±7 [2.2] | ND | |
| RifR/108 | 62 ±29 | 87 ±35 [1.4] | 250 ±190 [4.0] | 290 ±130 [4.7] | |
The three strain backgrounds are: (A) mismatch-repair proficient (mutL+), (B) mismatch-repair deficient (mutL::Tn5), and (C) mismatch-repair deficient (mutL::Tn5) plus dnaE915 (antimutator allele, see text). Mutant frequencies are based on the median value for 10–20 independent cultures (see Experimental procedures). In [brackets] the polAexo or polBex mutator effect defined as the increase in mutant frequency relative the pol+ strain.
Bold numbers indicate statistically significant values (P < 0.05, see Experimental procedures).
ND – not determined.
lac indicates the lac allele which reversion is being tested (see text).
The L and R orientations of the lac operon are as defined in Fijalkowska et al. (1998). The DNA strand in parentheses denotes the strand in which the presumed dominant mispair occurs for each of the four base substitutions (G·T for G·C→A·T, C·T for G·C→T·A, T·T for A·T→T·A, and T·G for A·T→G·C) (template base indicated first). See text and Fijalkowska et al. (1998) for a discussion.