TABLE 4

Rates of repeat-tract instability in strains containing conditional mlh1 mutations

26°35°
Relevant genotypeRate relative to wtAverageRate relative to wtAverage
Wild type1.3, 1.9, 0.3, 0.61.01.3, 1.7, 0.7, 0.8, 0.9, 0.9, 0.5, 1.31.0
Wild type + pEXO1, 2μ0.6, 0.8, 0.40.51.1, 1.3, 0.4, 1.0, 0.8, 2.0, 1.0, 0.41.0
Wild type + pSGS1, 2μNT4.0, 2.1, 1.92.7
mlh1Δ225, 183, 145, 1140423373, 392, 478, 555, 234, 497, 384, 492, 781465
mlh1Δ + pEXO1, 2μ310, 230, 83, 230213506, 784, 279, 284, 2409, 350, 285, 530, 413649
mlh1Δ + pSGS1, 2μNT365, 370, 622452
mlh1-T113A2.5, 1.0, 1.0, 1.21.4143, 155, 213, 184, 126, 370, 136, 121181
mlh1-T113A + pEXO1, 2μ0.6, 0.8, 0.4, 0.7, 0.70.7164, 160, 145, 52, 180, 256, 253, 85, 93154
mlh1-I147T1.0, 2.7, 1.7, 1.3, 1.41.6242, 87, 186, 112, 200, 88153
mlh1-I147T + pEXO1, 2μ0.6, 0.8, 0.6, 1.0, 1.00.8279, 84, 101, 57, 122129
mlh1-I147T + pSGS1, 2μNT99, 154126
mlh-F228S2.2, 2.0, 0.8, 2.21.8361, 177, 52, 180, 182, 265, 180, 172, 90184
mlh1-F228S + pEXO1, 2μ1.4, 1.4, 0.6, 0.81.1321, 232, 44, 99, 65, 98, 160, 90, 49129
mlh1-I296S5.7, 6.9, 2.8,1.3, 1.93.7237, 172, 317, 116, 364, 214, 208, 44, 170, 226, 110, 277, 80, 225, 146194
mlh1-I296S + pEXO1, 2μ1.3, 2.0, 2.5,1.5, 0.41.553, 98, 105, 84, 47, 80, 22, 93, 91, 69, 61, 4270
mlh1-I296S + pSGS1, 2μNT146, 229, 387, 176235
  • EAY774 (mlh1Δ) was transformed with pEAA109 (MLH1 ARSH4 CEN6)-derived plasmids carrying the indicated mlh1 alleles, pSH44, and one of the following three plasmids: pEAM81 (EXO1, 2μ), pEAM87 (SGS1, 2μ), or pRS423 (2μ). Rates per generation for repeat-tract instability were determined using the method of Lea and Coulson (1949) and are reported relative to EAY774 (mlh1Δ) transformed with pEAA109 and pRS423 at the respective temperature (1.34 × 10−5 at 26°, 1.15 × 10−5 at 35°). The repeat-tract instability for each independent experiment is presented (median of seven cultures). NT, not tested.