Yeast Transformation Kit

Product Description

The selection of plasmids in yeast is based on the use of auxotrophic mutant strains, which cannot grow without a specific medium component (an amino acid, purine, or pyrimidine). Transformation with a plasmid complementing the mutated gene enables the transformant to grow on medium lacking the required component. Yeast cells are made competent for transformation by incubation in a buffered lithium acetate solution. Transformation is then carried out by incubating the cells together with transforming DNA and carrier DNA in a solution containing polyethylene glycol (PEG). The Yeast Transformation Kit utilizes the lithium acetate method that was first introduced by Ito, et al. (1983). The protocols provided include modifications suggested by Hill et al. (1991), Gietz et al. (1992) ( protocol 1), and Elble (1992) (protocol 2).

Components

This kit is sufficient for over 100 standard transformations.

Reagents Required But Not Provided

• Sterile water
  
• Glucose, 50% solution, prepared from Product No. G5400, sterilized by 0.2 μm filtration
  
• Glycerol, 50% solution, prepared from Product No. G5516, sterilized by autoclaving
  
• DMSO, Product No. D8418 (optional)
  
• Bacteriological peptone, Product No. P0556
  
• Yeast extract, Product No. Y1625
  
• Bacteriological agar, Product No. A5306
  
• Yeast nitrogen base without amino acids, Product No. Y0626
  
• Yeast synthetic drop-out medium supplements without specific amino acids or pyrimidine:
  
  • Medium without leucine and tryptophan, Product No. Y0750
  • Medium without leucine, Product No. Y1376
  • Medium without histidine, Product No. Y1751
  • Medium without tryptophan, Product No. Y1876
  • Medium without histidine, leucine, tryptophan, and uracil, Product No. Y2001
• Yeast cells for use in transformation

Precautions and Disclaimer

This product is for R&D use only, not for drug, household, or other uses. Please consult the Safety Data Sheet for information regarding hazards and safe handling practices.

Storage/Stability

Store the kit at –20 °C. After thawing, store the Transformation Buffer, PLATE Buffer, and Yeast Synthetic Drop-out Medium Supplement Without Uracil at room temperature.

Procedures

Preparation of Media Solutions

1. YPD medium and plates - Used to maintain yeast strains under non-selective conditions.
   • 20 g/L Bacteriological peptone
   • 10 g/L Yeast extract
   • 20 g/L Bacteriological agar (for plates)

   Add 960 mL of deionized water, autoclave for 15 minutes, and add 40 mL of a 50% sterile (0.2 µm filtered)
   solution of glucose.

2. Synthetic Complete (SC) drop-out plates - Used to select yeast strains not requiring a certain medium
   component (amino acid, purine, or pyrimidine).
   • 0.8-1 g/L: Appropriate yeast synthetic drop-out medium supplement
     (Product No. Y1376, Y1751, Y1876, Y1501, Y0750, or Y2001)
   • 6.7 g/L: Yeast nitrogen base without amino acids
   • 20 g/L: Bacteriological agar

Add 960 mL of deionized water, autoclave for 15 minutes, and add 40 mL of a 50% sterile (0.2 µm filtered) solution of glucose. Autoclaving the yeast-agar solution longer will cause plates to become soft. Alternatively, the medium can be autoclaved longer if the agar is autoclaved separately from the yeast nitrogen base.

Yeast Strains Maintenance

Yeast strains can be stored at 4 °C for 2-3 months on YPD or SC plates sealed with Parafilm^®. For long term storage scrape a large inoculum from a freshly grown plate and resuspend in 1 mL of sterile 15% glycerol. Store at –70 °C.

To revive frozen yeast stocks, scrape frozen stock with a sterile toothpick or bacteriological needle and streak on the appropriate plate (YPD or SC). Avoid thawing the stock. If the stock has thawed, vortex well before refreezing.

Transformation Protocol 1

Preparation of competent cells

1. Inoculate yeast from YPD plate into 20 mL of YPD medium in a 100 mL sterile flask.
2. Grow overnight with shaking (200-250 rpm) at 30 °C. Culture should reach stationary phase (OD₆₀₀
3. Dilute culture into 100 mL of YPD medium in a 500 mL sterile flask, so that the OD₆₀₀ ∼0.3. Grow with shaking at 30 °C for 3-6 hours. The OD₆₀₀ of the culture should double at least once and should not pass 1.5.
4. Harvest cells by centrifugation at room temperature, 5 minutes at 5,000 rpm in a GSA or equivalent rotor.
5. Discard supernatant and resuspend cells in 50 mL of sterile water.
6. Repeat centrifugation as in Step 4.
7. Discard supernatant and resuspend in 1 mL of Transformation Buffer (Product Code T0809). Note: Cells are now ready for transformation. It is best to use cells immediately, but they can be kept at 4 °C for 1 week with a gradual decrease in competence or glycerol can be added to 15% and cells kept frozen at –70 °C.

Plasmid Transformation

1. Set up the required number of sterile 1.5 mL microcentrifuge tubes, one for each transformation and one for a negative control.
2. Aliquot 10 µL of 10 mg/mL salmon testes DNA (Product No. D9156) into each tube.
3. Add 0.1 µg of the yeast plasmid DNA to be studied (1 µL of 0.1 mg/mL) into each tube.
   Note: The Control Yeast Plasmid DNA (Product No. C4959) is supplied. The plasmid serves as a positive ura deficient yeast strain and the supplied Yeast Synthetic Drop-out Medium Supplement Without Uracil (Product No. Y1501).
4. Add 100 µL of competent cells and vortex.
5. Add 600 µL of PLATE Buffer (Product No. P8966) and vortex.
6. Incubate 30 minutes at 30 °C with shaking.
7. Optional: Add DMSO to 10%. This is not required, but will increase transformation efficiency 2-5 fold.
8. Heat shock for 15 minutes in a 42 °C heat block or water bath.
9. Spin 3 seconds in microcentrifuge and remove the supernatant. Do not spin longer as it will become hard to resuspend the cells.
10. Resuspend the cells in 500 µL of sterile water.
11. Plate 100 µL on appropriate SC selective plates without required supplement.
12. Incubate (face down) at 30 °C for 2-3 days until colonies appear.

Transformation Protocol 2 (Short)

This protocol is more rapid, but less efficient than Protocol 1. It is very convenient when only a small number of transformants are needed, but it is not recommended for transformations of libraries or other precious DNA.

1. Scrape a loop full of cells off a fresh plate (cells from a plate kept for 2 weeks at 4 °C will also besuitable) into a microcentrifuge tube.
2. Resuspend the cells in 0.5 mL of Transformation Buffer (Product No. T0809).
3. Spin 5 seconds in a microcentrifuge.
4. Remove the supernatant, leaving 50-100 µL of the buffer in tube.
5. Add 10 µL of 10 mg/mL salmon testes DNA (Product Code D9156) into each tube.
6. Add 1 µg of the yeast plasmid DNA to be studied and vortex 10 seconds.
   Note: The Control Yeast Plasmid DNA (Product No. C4959) is supplied. The plasmid serves as a positive control only for testing the transformation technique, using an ura deficient yeast strain and the supplied Yeast Synthetic Drop-out Medium Supplement Without Uracil (Product No. Y1501).
7. Add 600 µL of PLATE Buffer (Product No. P8966) and vortex.
8. Incubate 4-16 hours at room temperature.
9. Optional: Heat shock for 15 minutes in a 42 °C heat block or water bath.
10. Spin 3 seconds in microcentrifuge and remove the supernatant. Do not spin longer as it will become hard to
    resuspend the cells.
11. Resuspend cells in 500 µL of sterile water.
12. Plate 100 µL on appropriate SC selective plates without required supplement.
13. Incubate (face down) at 30 °C for 2-3 days until colonies appear.