The present invention relates to a transposon-based DNA integration system comprising (a) a transposon which is devoid of a polynucleotide encoding a functional transposase and which comprises a polynucleotide of interest, wherein the transposon comprises inverted repeats having a degree of identity with the repeats within SEQ ID NO: 2 and its inverted repeat, respectively, of at least 90%; and (b) a transposase having at its N-terminus a DNA binding domain comprising the sequences of SEQ ID NO: 3 and 4; or (c) a polynucleotide encoding the transposase of (b). The present invention further relates to a method of transferring a polynucleotide of interest into cells of a vertebrate comprising the step of introducing the transposon-based DNA integration system of the invention into said cells. In addition, the invention relates to a method of effecting RNAi comprising (a) stably introducing a transposon comprising an expression cassette expressing a short interfering RNA and a selectable marker gene as part of the transposon-based DNA integration system of the invention into a cell; (b) selecting for cells expressing the selectable marker; and (c) assessing whether the transcription/translation of the desired gene is effected by RNAi. A further embodiment of the invention is a method of gene trapping genes comprising the steps of (a) introducing the transposon-based DNA integration system of the invention into a cell; and (b) assessing for the expression of a selectable marker wherein expression of a selectable marker is indicative of integration of the transposon into a transcibed gene of the cell.