. 2000 May 23;97(12):6625–6629. doi: 10.1073/pnas.120168697

Table 4.

Activated Ras2 blocks [URE3] prion induction

Constructs	USA⁺ per 10⁶ cfu
Vector + vector	7
Vector + P_ADH1URE2	63
Vector + P_ADH1URE2ΔApaI	31,000
RAS2^Val19 + vector	0
RAS2^Val19 + P_ADH1URE2	0
RAS2^Val19 + P_ADH1URE2ΔApaI	400

Strain YHE869 (MATα ura2 leuΔ∷hisG trp1Δ∷hisG [ure-o]) was transformed with a centromeric TRP1 vector (pH341) or the same vector containing the constitutive active RAS2^Val19 allele (pH406). In addition, the strain was transformed with URE2 expression plasmids (pH7, 2 μ LEU2 P_ADH1, pH14, 2 μ LEU2 P_ADH1URE2; pH438, 2 μ LEU2 P_ADH1URE2ΔApaI). Three individual transformants for each combination were grown to saturation in medium without tryptophan or leucine. [URE3] generation was assayed by ability to grow on ammonium/USA medium and corrected for colony-forming units (cfu) per 100 cells. For strains carrying pH341 there were on average 30 cfu per 100 calculated cells. For strains carrying pH406 there were on average 9 cfu per 100 calculated cells. The average number of colonies per 10⁶ cfu after 5 days for the three transformants is given.