rtTA lentivirus (CMV, Puro) expresses an advanced version of tetracycline reverse transcriptional activator (rtTA) under the control of the CMV promoter, with puromycin as a selection marker. The rtTA binds to tetracycline operator elements (TetO) in the presence of doxycycline, causing transcriptional activation of genes downstream of TetO. rtTA lentivirus (CMV, Puro) can be used together with any lentivirus/construct with Tet responsive promoter.