Site-specific hydrolysis of DNA is common to many biological processes
. Three new structures, FokI, I-Crel and PI-SceI, were reported in the
past year, providing the first view of type IIs endonucleases and hom
ing endonucleases. Together, they reveal an extraordinary set of new m
echanisms by which endonucleases target the hydrolysis of specific DNA
sequences.