Table IV. Ess1 mutants are synthetically lethal with srb2 mutants.

Relevant genotype	5-FOARcolonies/total	CaESS1 plasmid lossa
ESS1 SRB2	742/10 992	68
ESS1 srb2Δ	620/7480	83
ess1H164R SRB2	286/25 050	11
ess1H164R srb2Δ	0/39 690	0

Strains of the indicated genotype carrying a functional ESS1 gene on a CEN-based URA3 plasmid were grown overnight in the absence of selection (in YEPD) and plated to 5-FOA-containing medium. All growth was at permissive temperature (30°C). 5-FOA^R colonies were scored versus the total number of colony-forming units (c.f.u.) as measured by duplicate platings to YEPD. The fraction of 5-FOA^R colonies reveals the frequency of plasmid loss (^a), which is given per 1000 c.f.u. The C.albicans ESS1 gene (CaESS1), which is functionally homologous to S.cerevisiae ESS1 (G.Devasahayam, V.Chaturvedi and S.D.Hanes, unpublished), was used to prevent unwanted recombination of the plasmid-borne copy of ESS1 and the chromosomal ess1^H164R allele.