Dnase I

DNase I is a versatile enzyme that nonspecifically cleaves DNA to release 5′-phosphorylated di-, tri-, and oligonucleotide products (1). A powerful research tool for DNA manipulations, DNase I is used in a range of molecularbiology applications. Some of its uses include:

1. Degradation of contaminating DNA after RNA isolation,

2. “Clean-up” of RNA prior to RT-PCR and after in vitro transcription, 
3. Identification of protein binding sequences on DNA (DNase I footprinting), 
4. Prevention of clumping when handling cultured cells, and 
5. Creation of a fragmented library of DNA sequences for in vitro recombination reactions. 

While frequently used in the laboratory, the activity of DNase I is still a mystery to many researchers. Are the “units” of one source of DNase I the same as that of another? Are calcium and magnesium ions required for activity? Will DNase I degrade DNA in DNA:RNA hybrids? Can DNase I remove 100% of DNA contamination from RNA preparations? In this article we will try to answer some of the questions surrounding this commonly used enzyme.


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