pcDNA3.1(+) and pcDNA3.1(-) are 5.4 kb vectors derived from pcDNA3 and designed for high-level stable and transient expression in mammalian hosts. High-level stable and non-replicative transient expression can be carried out in most mammalian cells. The vectors contain the following elements: • Human cytomegalovirus immediate-early (CMV) promoter for high-level expression in a wide range of mammalian cells • Multiple cloning sites in the forward (+) and reverse (-) orientations to facilitate cloning • Neomycin resistance gene for selection of stable cell lines • Episomal replication in cells lines that are latently infected with SV40 or that express the SV40 large T antigen (e.g. COS-1, COS-7). The control plasmid, pcDNA3.1/CAT, is included for use as a positive control for transfection and expression in the cell line of choice.