Abstract: Recombinant expression vectors are disclosed that include a control sequence for recombinant expression of proteins of interest; the control sequence combines a mCMV enhancer sequence with a rat EF-1alpha intron sequence or a human cytomegalovirus (huCMV) intron A sequence. Some of the vectors are useful for inducible expression. Some of the vectors contain a 5? PiggyBac ITR and a 3? PiggyBac ITR to promote genomic integration into a host cell chromosome. A method of selecting a stable production cell line for manufacturing a protein of interest is also disclosed. Also disclosed are mammalian host cells comprising the inventive recombinant expression vectors and methods of producing a protein of interest, in vitro, involving the mammalian host cell.