Artificial nucleases are designed for in vivo gene engineering, as the DNA cleavage performed
at a specific target site enhances the effectiveness of the cell’s DNA repair machinery. The
therapeutic potential of the above phenomenon stems from the knowledge that (i) the shifted reading
frame can be restored by non-homologous end-joining, or (ii) a DNA of erroneous sequence – causing
a genetic disease – can be corrected by homologous recombination in the presence of a suitable DNA
template. Besides the advantageous properties of the nowadays applied zinc finger nucleases, TALE
nucleases and the CRISPR/Cas9 system, they possess a residual citotoxicity. This is related to offtarget
cleavages, which could be prevented by the strict regulation of the enzymes. The studies on enzymes acting naturally
in a controlled manner are beneficial to get better insight into their mechanism. Such enzymes or their appropriate
domains may be the most promising alternatives to the presently applied ones. As an example, the DNA cleavage of the
inactive HNH nuclease mutants is inducible in a multiple way. This property may be used for establishing a control
mechanism and thus, in combination with specific DNA-binding domains they are good candidates for the catalytic site of
artificial nucleases. Here we collect the results on the properties of the HNH nucleases that allow for their redesign into
enzymes with possible therapeutic applications.
Keywords: Allosteric control, Artificial nuclease, CRISPR/Cas, HNH motif, TALE, zinc finger.
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