Genetic interactions of hypomorphic mutations in the m⁷G cap-binding pocket of yeast nuclear cap binding complex: An essential role for Cbc2 in meiosis via splicing of MER3 pre-mRNA

sto1Δ cbc2Δ double mutants give rise to spontaneous suppressors of slow growth. (A) Haploid progeny derived from tetrad dissection of a heterozygous diploid strain are shown. Spores from 11 tetrads were placed on YPD agar medium and incubated for 3 d at 30°C. The relevant genotype of the diploid is indicated at the top; A–D refers to colonies derived from sister spores; the segregation patterns of the markers for sto1Δ (hyg^R) and cbc2Δ (kan^R) are indicated below each tetrad: (T) tetratype, (PD) parental ditype, (ND) nonparental ditype. (B) The growth of wild-type cells was compared to that of sto1Δ cbc2Δ cells either taken from a colony immediately after germination or after continuous growth of individual haploids at 30°C and isolation of faster growing derivatives S1, S2, and S3. Cultures were adjusted to A₆₀₀ of 0.1 and aliquots (3 μL) of serial dilutions were spotted to YPD agar. Plates were photographed after 2 d of incubation at 30°C, 34°C, and 37°C, 3 d at 25°C, or 5 d at 20°C.