Use of a Bacterial Artificial Chromosome (BAC) as vector backbone for recombinant protein production. A) Schematic representation of the constructs used for protein production. CAGGS Fc is a conventional expression vector containing a CAGGS promoter, the Fc region of the human IgG1 gene, an IRES-eYFP-SV40 polyA reporter element and a PGK neomycin cassette. The Rosa26BAC CAGGS Fc construct was generated by recombining the CAGGS Fc vector into a BAC containing the Rosa26 locus. The CAGGS Fc vector was placed into the exon 2 of antisense transcript of the Rosa26 locus with 100 kb upstream and downstream sequence. B) Comparison of the efficacy in protein production between a conventional vector and a BAC-based vector. The Fc yield was analyzed in HEK 293 bulk cultures generated with the CAGGS Fc and Rosa26BAC CAGGS Fc vectors. The CAGGS Fc vector gave a yield of 0.5 pg/cell/day, while the BAC-based vector gave a yield of 5.7 pg/cell/day. Measurements were performed in triplicate. Error bars represent the standard deviation.