The transgene contains a tetracycline responsive element, comprising seven tandem copies of the tetracycline operator (tetO), driving bidirectional expression of cDNAs encoding human MYC (melanocytomatosis oncogene; also called c-myc)(exons 2-3) and cytosolic chicken ovalbumin (OVAL; also called SERPINB14) from oppositely-oriented human cytomegalovirus (CMV) minimal promoters.