Transient and stable transfection of Chinese hamster ovary cells with the recombinant feline erythropoietin gene and expression, purification, and biological activity of feline erythropoietin protein

Objective—To use transient and stable transfection of Chinese hamster ovary cells to clone the gene encoding feline erythropoietin (feEPO) protein, characterize the expressed protein, and assess its biological activity. Sample Population—Cultures of Chinese hamster ovary or TF-1 cells. Procedure—The gene encoding feEPO was cloned into a eukaryotic expression plasmid. Chinese hamster ovary cells were transiently or stably transfected with the plasmid. Expressed recombinant feEPO (rfeEPO) protein was purified from transiently transfected cells. The protein was characterized by use of SDS gel electrophoresis and western blot analysis. Biological activity was assessed by measuring thymidine incorporation by TF-1 erythroleukemic cells. Results—Purified rfeEPO from supernatants of transiently transfected cells was determined to be 34 to 40 kilodaltons (kd) by use of SDS gel electrophoresis, whereas the molecular weight predicted from the amino acid sequence was 21.5 kd. The banding pattern and high molecular we...