Yeast strains containing the indicated plasmids were struck to solid media containing 200 μg/ml methotrexate or its solvent, DMSO, as indicated, and were grown at 30°. The negative control strain was DY2219, the positive control strain was DY2315, the strain with two Nab3134-fusion proteins was DY2214, and that with two full-length Nab3-fusion proteins was DY2217.