Chromagenics B.v.

Richard G A B Sewalt

Arie Pieter Otte

Theodorus H J Kwaks

Henricus J M Van Blokland

The invention provides a DNA molecule comprising a multicistronic transcription unit coding for i) a polypeptide of interest, and for ii) a selectable marker polypeptide functional in a eukaryotic host cell, wherein the polypeptide of interest has a translation initiation sequence separate from that of the selectable marker polypeptide, and wherein the coding sequence for the polypeptide of interest is upstream from the coding sequence for the selectable marker polypeptide in the multicistronic transcription unit, and wherein an internal ribosome entry site is present downstream from the coding sequence for the polypeptide of interest and upstream from the coding sequence for the selectable marker polypeptide, and wherein the nucleic acid sequence coding for the selectable marker polypeptide in the coding strand comprises a GTG or a TTG start codon. Also provided are methods for obtaining host cells expressing a polypeptide of interest, such host cells comprising DNA molecules of the invention. Further provided is the production of polypeptides of interest, comprising culturing host cells comprising the DNA molecules of the invention.

Selection of host cells expressing protein at high levels

The invention provides a DNA molecule comprising a multicistronic transcription unit coding for i) a selectable marker polypeptide functional in a eukaryotic host cell, and for ii) a polypeptide of interest, the polypeptide of interest having a translation initiation sequence separate from that of the selectable marker polypeptide, characterized in that the coding sequence for the polypeptide of interest is downstream from the coding sequence for the selectable marker in the multicistronic transcription unit, and the nucleic acid sequence coding for the selectable marker polypeptide comprises a mutation that decreases the translation efficiency of the selectable marker in a eukaryotic host cell. The invention also provides methods for obtaining host cells expressing a polypeptide of interest, the host cells comprising the DNA molecules of the invention. The invention further provides the production of polypeptides of interest, comprising culturing host cells comprising the DNA molecules according to the invention.

The invention provides a DNA molecule comprising an open reading frame sequence that encodes a selectable marker polypeptide, wherein said DNA molecule in the coding strand comprises a translation start sequence for the selectable marker polypeptide having a GTG startcodon or a TTG startcodon, and wherein the open reading frame sequence that encodes the selectable marker protein has been mutated to replace at least half of its CpG dinucleotides as compared to the native open reading frame sequence that encodes the selectable marker protein.

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Arnhem, Netherlands

Richard G A B Sewalt