Table 2.

Rescue of rad22-H6 and Δrad22 cells by rti1⁺

Plasmid	Colony formation at 36°C of rad22-H6	Suppression of Δrad22 sensitivity to		Suppression of Δrad22 sterility	Suppression of mating type switch lethality of Δrad22
		UV	bleomycin (%)
pALSK	<0.03	<0.04	0.05	<0.01	<0.02
pALSK-rad22+	37.0	50.3	19.9	8.5	14.0
pALSK-rti1+	18.2	15.5	4.8	2.7	5.1

The rad22-H6 (HM366) cells were transfected with the indicated plasmids and selected on MMA plates at 36°C. The ratio of the number of leu⁺ colonies formed at 36°C to that formed at 23°C was expressed as percent colony formation. The h⁺ Δrad22 (HM367) cells stably transfected with the indicated plasmids were plated on MMA plates at a density of 500 cells per plate, exposed to 120 J/m² of UV, and incubated at 23°C for 7 d. Sensitivity to 0.1 mg/ml bleomycin was assayed as described in Figure 2A. The h⁺ Δrad22 (HM367) and h⁻ Δrad22 (HM375) cells each harboring the indicated plasmid were mixed together and incubated in nitrogen-free PM medium at 23°C for 15 h. Suppression of sterility is expressed as percentage of mated cells in the total population. The h⁺ Δrad22 (HM367) cells harboring the indicated plasmid were mated with the h⁹⁰ rad22⁺ (K153-B4) cells in nitrogen-free PM medium at 28°C for 24 h. Formed asci were treated with 30% ethanol, and ura⁺ leu⁺ spores were allowed to grow on MMA plates. Each colony was determined for mating type. A total 500 colonies for each plasmid were examined. The ratio of the number of h⁹⁰ colonies to the number of h⁺ colonies was expressed as percent suppression of mating type switch lethality.