Ata were parsed from the set of PDB files available as of November 2012. Chains were counted rather than PDB Title Loaded From File entries as expression information is recorded by chains in the PDB. doi:10.1371/journal.pone.0068674.gthan in bacteria. Thus a profound screening for the best protein construct as well as the most appropriate host regarding both yield and quality of protein is essential. To address this, vectors for initial screenings harbouring promoters for different expression systems have been reported before [14,15]. However, these plasmids suffer some major drawbacks that limit their usability in multiparallel expression studies in state-of-the art systems. For instance, they are not compatible to advanced transposition based techniques for the generation of recombinant bacmids [16] and novel systems emerged thereof such as MultiBac [17] or Acembl [18]. Moreover, they lack the EBVoriP for enhanced expression in optimised HEK293-6E cells and are not applicable for stable genomic expression in mammalian cells by the Flp-recombinase mediated cassette exchange system (RMCE). In this report we present the construction and evaluation of the versatile shuttle vector pFlp-Bac-to-Mam (pFlpBtM) that can be used for both, fast transient and stable genomic expression in mammalian cells as well as a donor vector for the generation of recombinant bacmids. By the unique combination of genetic elements it streamlines the initial screening for expressible constructs and the most suitable host for 1315463 any given protein. We demonstrate the applicability of this vector for the production of three different classes of eukaryotic model proteins. Accumulation of an intracellular model protein was validated by the expression of mCherry, a mutant of Discosoma striata red fluorescent protein [19]. A single-chain-Fv-hIgG1Fc fusion construct (scFv-Fc) [20] was used as a member of a well-known class of secretory therapeutic proteins that routinely are expressed with high-yields in mammalian cells. Additionally, the extracellular Title Loaded From File domain (ECD aa 1?78) of the murine Toll like receptor 2 was chosen as a second secreted model protein. As a member of the Leucine Rich Repeat (LRR) family of proteins this construct represents a challenging target protein for heterologous expression since it can only be produced in low amounts by using elaborate expression strategies [21].esis to remove a BbsI-site within the promoter region, a PCR fragment containing the FRT-Cassette generated from the vector pFS-sighis-PGK (GenBank JF313343) flanked by BamHI at the 59 end and AvrII at the 39 end, was integrated into the modified pFastbac with the hr5-ie1-p10 promoter. The resulting intermediate construct (pFlpBtM-I, Genbank ID: KC991096) can be used as donor vector in BEVS and for RMCE. The final pFlpBtM-II vector (Genbank ID: KC991095) was constructed by replacing the hr5-ie1-p10 promoter region by a PCR-fragment harbouring the CMV-p10-T7 promoter region from pTriEx (Novagen). The backbone of the resulting vector was excised by SapI-EcoRV digestion and replaced by a PCR-fragment of a modified pTT5 backbone (NRCC) containing the EBNA1 oriP, a beta-lactamase gene and a pMB-ori. Prior to this integration both an NcoI and a BbsI site in the backbone of pTT5 were deleted by site-directed mutagenesis.Integration of Model ProteinsFor the intracellular accumulation of the model protein mCherry (gb AY678264), the corresponding gene was integrated into both pFlpBtM-I and pFlpBtM-II through a PCR-fragment.Ata were parsed from the set of PDB files available as of November 2012. Chains were counted rather than PDB entries as expression information is recorded by chains in the PDB. doi:10.1371/journal.pone.0068674.gthan in bacteria. Thus a profound screening for the best protein construct as well as the most appropriate host regarding both yield and quality of protein is essential. To address this, vectors for initial screenings harbouring promoters for different expression systems have been reported before [14,15]. However, these plasmids suffer some major drawbacks that limit their usability in multiparallel expression studies in state-of-the art systems. For instance, they are not compatible to advanced transposition based techniques for the generation of recombinant bacmids [16] and novel systems emerged thereof such as MultiBac [17] or Acembl [18]. Moreover, they lack the EBVoriP for enhanced expression in optimised HEK293-6E cells and are not applicable for stable genomic expression in mammalian cells by the Flp-recombinase mediated cassette exchange system (RMCE). In this report we present the construction and evaluation of the versatile shuttle vector pFlp-Bac-to-Mam (pFlpBtM) that can be used for both, fast transient and stable genomic expression in mammalian cells as well as a donor vector for the generation of recombinant bacmids. By the unique combination of genetic elements it streamlines the initial screening for expressible constructs and the most suitable host for 1315463 any given protein. We demonstrate the applicability of this vector for the production of three different classes of eukaryotic model proteins. Accumulation of an intracellular model protein was validated by the expression of mCherry, a mutant of Discosoma striata red fluorescent protein [19]. A single-chain-Fv-hIgG1Fc fusion construct (scFv-Fc) [20] was used as a member of a well-known class of secretory therapeutic proteins that routinely are expressed with high-yields in mammalian cells. Additionally, the extracellular domain (ECD aa 1?78) of the murine Toll like receptor 2 was chosen as a second secreted model protein. As a member of the Leucine Rich Repeat (LRR) family of proteins this construct represents a challenging target protein for heterologous expression since it can only be produced in low amounts by using elaborate expression strategies [21].esis to remove a BbsI-site within the promoter region, a PCR fragment containing the FRT-Cassette generated from the vector pFS-sighis-PGK (GenBank JF313343) flanked by BamHI at the 59 end and AvrII at the 39 end, was integrated into the modified pFastbac with the hr5-ie1-p10 promoter. The resulting intermediate construct (pFlpBtM-I, Genbank ID: KC991096) can be used as donor vector in BEVS and for RMCE. The final pFlpBtM-II vector (Genbank ID: KC991095) was constructed by replacing the hr5-ie1-p10 promoter region by a PCR-fragment harbouring the CMV-p10-T7 promoter region from pTriEx (Novagen). The backbone of the resulting vector was excised by SapI-EcoRV digestion and replaced by a PCR-fragment of a modified pTT5 backbone (NRCC) containing the EBNA1 oriP, a beta-lactamase gene and a pMB-ori. Prior to this integration both an NcoI and a BbsI site in the backbone of pTT5 were deleted by site-directed mutagenesis.Integration of Model ProteinsFor the intracellular accumulation of the model protein mCherry (gb AY678264), the corresponding gene was integrated into both pFlpBtM-I and pFlpBtM-II through a PCR-fragment.
