Table 1.

Summary of in vivo and in vitro phenotypes of point mutants in the GQ motif

MutationSenescenceaTelomeresbPrimer extension activityc
None+++100
D66A+70
G85A+8
D93A+++140
N104AV105A+80
W115A++/−<2
F118AH119A++/−<2
G123A++/−<2
Q138AF139A+5
G141A+6
E154A+++100
  • a Senescent strains (+) grew slowly on the initial transformation plate and gave rise to small colonies that are the same size as those from an Δest2 strain transformed with the pSE358 vector.

  • b Telomere lengths were determined in Southern hybridization assays (Fig. 2) and were scored as follows: +++, wild-type telomere length; +, on average about 150 to 200 bp shorter; +/−, on average about 300 bp shorter with weak hybridization signals.

  • c Primer extension assays were performed using TEL66 as primer under standard conditions. Each mutant fraction was assayed alongside the wild-type fraction. The signals obtained from the mutant fractions were normalized against that from the wild-type fraction, which was taken as 100.