Mammalian expression vectors with modulatable promoters and two multiple cloning sites.

To facilitate the use of a wide range of selectable markers in transfection studies with human cells, in conjunction with the use of modulatable promoters for regulated expression of the genes of interest, we constructed two pUC19-based mammalian expression vectors, each containing two lacZ alpha-based multiple cloning sites (MCS). Selectable markers can be inserted into the MCS derived from pUC19, and the recombinants can be screened by lacZ complementation. The genes of interest can be inserted into the second MCS. The new MCS contains an amber stop codon in-frame with translation of the LacZ alpha-peptide. The presence of insert in the second MCS can also be screened on XGal plates, but in an Escherichia coli host containing an amber suppressor gene. Expression of the genes of interest can be modulated through transcription from the promoter of the mouse metallothionein-I-encoding gene or the long terminal repeat of the mouse mammary tumor virus. These vectors, as well as several of the intermediate plasmids described in this report, can be used to clone any two genetic elements into a single plasmid.