Hyperactive variants of the transposase protein of the transposon system Sleeping Beauty

A method for producing a protein encoded by a transposon, comprising providing a gene transfer system comprising

• a) a polypeptide variant of sleeping beauty 10 (SB10) transposase or an isolated nucleic acid encoding a variant of SB10 transposase, wherein said variant comprises an amino acid sequence differing from the sequence of SB10 transposase of SEQ ID NO:
• 1 by 1-20 amino acids and at least the following mutation:
• K14R;
• and
• b) a transposon comprising a nucleic acid sequence positioned between at least two repeats, wherein the repeats are inverted repeats (IRs) and/or inverted repeats/direct repeats (IR/DRs), wherein the repeats can bind to the SB10 polypeptide variant, wherein the protein is encoded by the nucleic acid sequence positioned between the at least two repeats;
• providing a target mammalian cell;
• and
• transfecting the target mammalian cell with the gene transfer system to produce a transfected target mammalian cell and
• expressing the protein.