Selective yeast medium

Agar

Amino acid mix

3-Aminotriazole (3AT; Sigma)

Ammonium sulfate (US Biological)

Histidine-HCl (100 mM, sterile; US Biological)

Leucine (100 mM, sterile; US Biological)

NaOH (10 M)

Tryptophan (40 mM, filter sterilized; US Biological)

Uracil (20 mM, sterile; Sigma)

Yeast nitrogen base (US Biological)

To make 2 liters solid medium:

1. Mix 2.6 g amino acid mix (-Leu, -His, - Trp, -Ura), 3.4 g yeast nitrogen base, and 10 g ammonium sulfate in a 2-liter flask. Add a stir bar.
2. Dissolve this mixture in 950-ml H₂O.
3. Adjust the pH to 5.9 by adding 10 M NaOH.
4. Add 35 g agar and 900 ml H₂O to a second 2-liter flask.
5. Autoclave both flasks 60 minutes.

For DNA bait::HIS3 integration or Y1H screens, we add 3AT to media lacking histidine after autoclaving.
6. Carefully pour the content of the medium flask into the agar flask.
7. Cool at 55°C (in a water bath) for at least 1 hour.
8. Add 100-ml sterilized 40% (w/v) glucose solution.
9. Add 16 ml of each of the required amino acids or nucleotides (from stock solutions: sterilized 100 mM histidine-HCl, sterilized 20 mM uracil, sterilized 100 mM leucine and filter-sterilized 40 mM tryptophan), while mixing the medium on a stir plate. (For example, for Sc-His plates, add 16 ml of uracil, leucine, and tryptophan solutions.)
10. Pour into 15-cm Petri dishes, ~80 ml/dish.
11. Dry for 3-5 days at room temperature, wrap in plastic bags or foil, and store at room temperature.