A method for engineering I-CreI homing endonuclease variants able to cleave mutant I-CreI sites having variation in positions ±8 to ±10. A I-CreI homing endonuclease variant obtainable by said method, a vector encoding said variant, a cell, an animal or a plant modified by said vector. Use of said I-CreI endonuclease variant and derived products for genetic engineering, genome therapy and antiviral therapy.