Patent ID: 8841089

Claim:
A method for expressing at least one polynucleotide of interest, comprising: a) co-introducing into mammalian host cells (i) a first polynucleotide encoding a modified selectable marker gene having a reduced selection potential, (ii) a second polynucleotide comprising a first nucleic acid sequence for a Matrix Attachment Region (MAR) element which is capable of enhancing expression of at least one polynucleotide of interest, and at least one second nucleic acid sequence comprising a curved origin motif, and (iii) said at least one polynucleotide of interest encoding a polypeptide of interest; and b) cultivating said cells to express said at least one polynucleotide of interest, wherein said first polynucleotide encoding a modified selectable marker gene having a reduced selection potential is a polynucleotide encoding a modified neomycin phosphotransferase, and wherein said modified neomycin phosphotransferase has an amino acid substitution at A to G and T to S at positions 224 and 225 as compared to an unmodified neomycin phosphotransferase of SEQ ID NO: 35.