TABLE 1.

Yeast strains used in this study

Strain	Genotype	Source
PN559	h− leu1-32 ura4-D18 ade6-M216	P. Nurse's lab collection
PN2490	h+ ura4-D18 rhp51Δ∷kanR	P. Nurse's lab collection
PN3773	h+ leu1-32 ura4-D18 his3-D1 ade6-M210 pku70Δ∷ kanR	Baumann and Cech (2000)
KT1a0	h+ leu1-32 ura4-D18 ade6-M210 lig4Δ∷LEU2	Tomita et al. (2003)
KT120	h+ leu1-32 ura4-D18 ade6-M210 rad50Δ∷LEU2	Tomita et al. (2003)
AD459	h− leu1-32 ura4-D18 ade6-M216 lig4Δ∷LEU2	PN559 × KT1a0
AD462	h+ leu1-32 ura4-D18 ade6-M216 lig4Δ∷LEU2 pku70Δ∷ kanR	AD459 × PN3773