A concatemer of sleeping beauty transposable elements each consisting of optimized inverted repeat direct repeat sequence specific for sleeping beauty transposase flanking splice acceptor sites (from engrailed-2, these are larger than those in the T2/Onc construct) and poly A signals in both orientations. Between the splice acceptor sites is 5' long terminal repeat sequence from the murine stem cell virus followed by a splice donor site. This construct can create both loss-of-function and gain-of-function mutations. Lines were selected for high copy number and lack of transposable element methylation. In line 6113 the concatemer integrated into the proximal region of chromosome 1.