Homing endonuclease

Crystal structure of I-CreI bound to its DNA recognition sequence. The enzyme binds as a homodimer; one subunit is depicted in yellow, the other in pink. The enzyme is shown in surface representation; DNA molecule is shown as a collection of spheres, each colored according to its chemical element.

The homing endonucleases are a collection of endonucleases encoded either as freestanding genes within introns, as fusions with host proteins, or as self-splicing inteins. They catalyze the hydrolysis of genomic DNA within the cells that synthesize them, but do so at very few, or even singular, locations. Repair of the hydrolyzed DNA by the host cell frequently results in the gene encoding the homing endonuclease having been copied into the cleavage site, hence the term 'homing' to describe the movement of these genes. Homing endonucleases can thereby transmit their genes horizontally within a host population, increasing their allele frequency at greater than Mendelian rates.