The invention refers to recombinant DNA plasmid vector containing cDNA encoding human EPO of clone lambda HEPOFL13 (ATCC 40153) and mammalian cell transformed with this vector or with a plasmid which contains the entire bovine papilloma virus DNA and the cDNA sequence of Table 3 coding for human EPO are which useful in the preparation of recombinant human erythropoietin which is characterized by the presence of O-linked glycosilation.