Figure 3. DBP2 displays genetic interactions with mRNA export factor mutants mex67-5 and yra1ΔN.

(A) Overexpression of DBP2 is lethal in mex67-5 strains. Indicated strains were transformed with empty vector or galactose-inducible pGAL-DBP2. Resulting transformants were then spotted in 5-fold serial dilutions onto transcriptionally repressive (glucose) or inducing (galactose) media and subsequently grown at the indicated temperatures from 25–35 °C. (B) Overexpression of DBP2 in the mex67-5 strain induces a mRNA export defect at the mex67-5 permissive temperature. Briefly, yeast strains were grown at 25 ˚C to mid log phase in selective media and then shifted to galactose-containing media for 1 hour to induce DBP2 overexpression. Cells were then harvested and in situ hybridization was conducted with oligodT₃₀ to visualize accumulation of total poly(A)+ RNA. DAPI staining of DNA shows the position of the nucleus. (C) Loss of DBP2 in yra1ΔN strain results in a synthetic sick growth defect. The indicated double mutant strains were constructed using standard methods and were analyzed for growth defects as above by serial dilution analysis onto rich media. The dbp2Δ displays a cold sensitive phenotype as previously described ¹⁸.