MUTUAL ACTIVATION OF 2 RESTRICTION ENDONUCLEASES - INTERACTION OF ECOP1 AND ECOP15

Type III restriction endonucleases recognize nonsymmetric nucleotide s equences. A necessary condition for DNA cleavage is the presence of tw o unmethylated recognition sites which are inversely ('head-to-head') oriented in the DNA double strand. A DNA substrate possessing one EcoP 1 and one EcoP15 site in the head-to-head configuration could not be c leaved by the individual enzymes, however, it was specifically digeste d in the simultaneous presence of both enzymes. In agreement with the tracking-collision model for the DNA interaction of type III enzymes c leavage could be abolished by Lac repressor bound between the two site s. We conclude that two different type III enzymes can functionally co operate in the cleavage of DNA.