Objective: In order to coordinately express amarker gene and therapeutic genes in one vector, apolycistronic retroviral vector was constructed withthe internal ribosome entry site from encephalo-myocarditis and polio virus, which was able to expressthree different genes simultaneously. Methods: Thevector used mouse moloney leukemia virus sequencesfor viral expression and packaging functions and Objective: In order to coordinately express a marker gene and therapeutic genes in one vector, apolycistronic retroviral vector was constructed with the internal ribosome entry site from encephalo-myocarditis and polio virus, which was able to expressthree different genes simultaneously. Methods: Thevector used mouse moloney leukemia virus sequencesfor viral expression and packaging functions and