The invention relates to a nucleic acid molecule encoding a fusion protein, said nucleic acid molecule comprising, in transcription direction 5 ́---3 ́, at least: one nucleic acid sequence encoding a DNA-binding domain; and a nucleic acid sequence encoding a FokI-type catalytic domain, the 3' end thereof comprising a nucleic acid sequence encoding a peptide comprising between 18 and 23 amino acids. The invention also relates to a fusion protein that can be obtained, for example, from the transcription of said molecule, and to a method for altering the genetic material of a cell using said molecule or protein.