Elimination of RNA Contamination by Traditional Enzymatic Digestion Method.
RNA contamination in DNA was typically removed by RNase A and RNase T1 digestion.
22 Briefly, 2 μL of RNase T1 (25 Units/μL) and 10 μL of RNase A (10 mg/mL) were added to an aliquot of 150 μL of genomic DNA (100 μg) isolated from yeast cells, and then, the mixture was incubated at 37 °C for 6 h followed by successive extraction with phenol/chloroform (1:1, v/v) and chloroform twice,respectively.
Then, the aqueous layer was taken out, and 0.1 volume of 3 M sodium acetate buffer (pH 5.2) and 1 volume of ice cold isopropanol were added. After kept at −20 °C for 30 min, DNA was precipitated by centrifuging at 12 000 under 4 °C for 15 min. The DNA pellet was subsequently washed with 70% ethanol for three times.
The supernatant of 70% ethanol was carefully removed, and the tube was allowed to air-dry with
the lid open for 30 min.
The resultant DNA was then dissolved in Tris-HCl buffer (pH 8.0) for the following treatments.