Magnesium-dependent thermostability of DNase I.

DNase I can be used to remove contaminating DNA from RNA samples. Heat treatment has been recommended as a method to inactivate DNase I enzymatic activity, thereby allowing subsequent reverse transcription and PCR amplification of DNase I treated RNA. We have found that inactivation of DNase I by heat treatment is strongly dependent on Mg2+ concentration. In addition, deoxyribonucleolytic activity of "inactivated" enzyme may be restored by changes in Mg2+ concentration following heat treatment. Caution should be exercised when using heat treatment alone as a method of DNase I inactivation.