Expression of a synthetic human interferon-alpha 1 gene with modified nucleotide sequence in mammalian cells

We have constructed a recombinant interferon (IFN) gene whose coding region is a chemically synthesized human (Hu)IFN-alpha 1 gene [Edge et al., Nature 292 (1981) 756-762] encoding the same protein as its natural counterpart while possessing important modifications. These modifications were introduced in order to: change codon usage, destroy integrity of repeated and complementary oligodeoxynucleotides in the coding region, introduce an intron, substitute other sequences for the IFN specific 3'- and 5'-flanking sequences and remove the leader sequence (which encodes for the signal peptide). We report here on the transfection and isolation of murine cells which contain low-copy-number insertions of our recombinant gene. These lines maintain a high steady-state level of biologically active HuIFN-alpha in the cytoplasm, produced from mRNAs of Mr expected for correctly processed transcripts. These results show directly that the leader sequence is essential for secretion of IFN proteins. They also argue against a crucial role of the particular features of the transcribed sequence of the natural HuIFN-alpha 1 gene in regulating its expression.