Patent ID: 7214532

Claim:
A DNA construct useful in homologous recombination, comprising: (i) a pair of flanking DNA sequences which are homologous to regions of the human gene which encodes erythropoietin, said regions being selected from the group consisting of 5′-untranslated sequences, a modified portion of exon 1, and intron 1, to permit homologous recombination, said modified portion of exon 1 corresponding to the first four codons of the signal sequence coding region, and coding for a sequence of four amino acids of formula Met Xaa Xaa Xaa (SEQ ID NO: 5) wherein the first Xaa is Gly or Ser, the second Xaa is Ala, Val, Leu, Ile, Ser or Pro, and the third Xaa is Pro, Arg, Cys or His, with the proviso that said four amino acid sequence is not Met Gly Val His (SEQ ID NO: 6). (ii) a gene which codes for a positive selection marker, and (iii) a heterologous expression control sequence which comprises a promoter.