Abstract: A recombinant antibody vector for producing a single chain recombinant antibody comprises: (a) a contiguous nucleotide sequence: (i) that comprises a restriction endonuclease site that encodes an amino acid sequence of an immunoglobulin variable region; and (ii) that encodes an immunoglobulin constant region amino acid sequence in the same reading frame as (i), wherein another nucleotide sequence encoding (iii) an immunoglobulin variable region amino acid sequence, is insertable into the restriction endonuclease site in the same reading frame as (ii); and (b) one or more regulatory nucleotide sequences operably linked or connected to said nucleotide sequence, wherein the amino acid sequence in (i) comprises amino acids conserved in different immunoglobulin variable regions. The restriction endonuclease site may be a SacI site which encodes the conserved amino acids glutamate and leucine. In frame insertion of the nucleotide sequence of (iii) is facilitated by ligase independent cloning.

Abstract: The present invention relates to protein expression systems and in particular to a mammalian protein expression system. Specifically, the present invention provides a rodent cell line with enhanced protein production capabilities. The invention also relates to eukaryotic cloning and expression vectors and related methods, and in particular to DNA vectors capable of high level expression of a protein of interest. The invention allows for long-term episomal maintenance of expression vectors in mammalian cells.