pLVX-EF1α-DsRed-Monomer-C1 is an HIV-1-based, lentiviral expression vector designed to constitutively express a protein of interest fused to the C-terminus of DsRed-Monomer, a monomeric mutant of the Discosoma sp. red fluorescent protein DsRed (1). The excitation and emission maxima of native DsRed-Monomer are 557 nm and 585 nm, respectively. Stable, constitutive expression of the fusion protein is driven by the EF1α promoter (PEF1α), which continues to be constitutively active even after the vector integrates into the host cell genome (2).

pLVX-EF1α-DsRed-Monomer-C1 contains all of the viral processing elements necessary for the production of replication-incompetent lentivirus, as well as elements to improve viral titer, transgene expression, and overall vector function. The woodchuck hepatitis virus posttranscriptional regulatory element (WPRE) promotes RNA processing events and enhances nuclear export of viral RNA (3), leading to increased viral titers from packaging cells. In addition, the vector includes a Rev-response element (RRE), which further increases viral titers by enhancing the transport of unspliced viral RNA out of the nucleus (4). Finally, pLVX-EF1α-DsRed-Monomer-C1 also contains a central polypurine tract/central termination sequence element (cPPT/CTS). During target cell infection, this element creates a central DNA flap that increases nuclear import of the viral genome, resulting in improved vector integration and more efficient transduction (5). In addition to lentiviral elements, pLVX-EF1α-DsRed-Monomer-C1 contains a puromycin resistance gene (Puror) under the control of the murine phosphoglycerate kinase (PGK) promoter (PPGK) for the selection of stable transductants. The vector also contains a pUC origin of replication and an E. coli ampicillin resistance gene (Ampr) for propagation and selection in bacteria.