THE PROTEIN SPLICING DOMAIN OF THE HOMING ENDONUCLEASE PI-SCEI IS RESPONSIBLE FOR SPECIFIC DNA-BINDING

The homing endonuclease PI-SceI consists of a protein splicing domain (I) and an endonucleolytic domain (II). To characterize the two domain s with respect to their contribution to DNA recognition we cloned, pur ified and characterized the isolated domains. Both domains have no det ectable endonucleolytic activity. Domain I binds specifically to the P I-SceI recognition sequence, whereas domain II displays only weak non- specific DNA binding. In the specific complex with domain I the DNA is bent to a similar extent as observed with the initial complex formed between PI-SceI and DNA. Our results indicate that protein splicing do main I is also involved in recognition of the DNA substrate.