A transposase encoded by the Tol2 element; a polynucleotide encoding the
same; a method of modifying the gene structure of a cell (preferably a
vertebrate cell) by using the above protein; a method of modifying the
function of a cell by modifying the gene structure thereof; and a cell
having been modified in function by these methods. Also the structure of
a cis element necessary in gene transfer is clarified and presented.