Heat shock protein 1 (formerly Hsp25) antisense RNA and E. coli beta-galactosidase are co-expressed under control of the tetracycline operator/response element, permitting induction or repression of their expression by doxycycline in mice bearing this and a second transgene expressing the tetracycline reverse transactivator (rtTA) or transactivator (tTA) protein. (J:82809)