DNase I

DNase I (Deoxyribonuclease I) is an enzyme that catalyzes the hydrolytic cleavage of DNA (deoxyribonucleic acid) into smaller oligonucleotides. It is an endonuclease that attacks phosphodiester bonds within the DNA molecule, producing nucleotides and oligonucleotides. DNase I is widely used in molecular biology laboratories for various applications, including the removal of DNA from RNA preparations and the digestion of genomic DNA to prevent clumping in cell cultures.

Function

DNase I plays a crucial role in the natural turnover of DNA in cells, aiding in the removal of DNA during apoptosis (programmed cell death) and in the clearance of extracellular DNA in the bloodstream and tissues. This function is essential for maintaining cellular homeostasis and preventing the immune system from reacting to self-DNA, which could lead to autoimmune diseases.

Structure

The enzyme is a monomeric protein that requires divalent cations, such as Mg^2+ or Ca^2+, for its activity. The structure of DNase I has been extensively studied, revealing a compact globular form with a deep groove that accommodates the DNA substrate.

Applications

In the laboratory, DNase I is used for several purposes:

• Removing DNA from RNA preparations to ensure the purity of RNA for experiments such as reverse transcription polymerase chain reaction (RT-PCR).
• Facilitating the digestion of genomic DNA in cell lysates to prevent viscosity and improve protein extraction efficiency.
• In recombinant DNA technology, DNase I is used to randomize DNA sequences or to trim DNA fragments for cloning purposes.

Clinical Significance

DNase I has therapeutic applications, particularly in the treatment of cystic fibrosis. The enzyme is used in a recombinant form (dornase alfa) as an inhaled medication to digest extracellular DNA in the mucus of patients, thereby reducing viscosity and improving lung function.

Safety and Handling

While DNase I is invaluable in research and therapy, it must be handled with care in the laboratory to avoid unintended degradation of DNA samples. Precautions include using dedicated pipettes and tubes and working in a DNase-free environment.

See Also

• Nuclease
• Cystic Fibrosis
• Recombinant DNA
• Apoptosis