pLVX-IRES-tdTomato is an HIV-1-based, lentiviral expression vector that allows the simultaneous expression of your protein of interest and tdTomato in virtually any mammalian cell type, including primary cells. tdTomato is a member of the family of fruit fluorescent proteins derived from the Discosoma sp. red fluorescent protein, DsRed . The vector expresses the two proteins from a bicistronic mRNA transcript, allowing tdTomato to be used as an indicator of transduction efficiency and a marker for selection by flow cytometry.Expression of the bicistronic transcript is driven by the constitutively active human cytomegalovirus immediate early promoter (PCMV IE) located just upstream of the MCS. An encephalomyocarditis virus (EMCV) internal ribosome entry site (IRES), positioned between the MCS and tdTomato, facilitates cap-independent translation of tdTomato from an internal start site at the IRES/tdTomato junction .
   pLVX-IRES-tdTomato 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 , 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 . Finally, pLVX-IRES-tdTomato 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. The vector also contains a pUC origin of replication and an E. coli ampicillin resistance gene (Ampr ) for propagation and selection in bacteria.