The porcine erythropoietin gene: cDNA sequence, genomic sequence and expression analyses in piglets.

The porcine erythropoietin (EPO) gene and its cDNA have been cloned and characterized. The cDNA encodes a protein of 194 amino acids. The gene structure and sequence show a high degree of homology to the corresponding human and murine gene. Steroid hormone receptor binding sites are present both in the promoter and in the 3' flanking region of the gene, which also contains an oxygen-sensing sequence. The promoter lacks classical promoter elements such as TATA and CAAT boxes. Expression analyses using a competitive RT-PCR assay showed that the kidneys contain about ten times more erythropoietin mRNA than the liver in five-week-old piglets, thus indicating that the shift from mainly hepatic to mainly renal EPO production has taken place at this age. The testes showed a higher ratio of EPO mRNA to total RNA than the liver. Spleen showed very low levels of expression, while no expression of erythropoietin mRNA was detected in brain tissue, bone marrow, lung, lymph nodes, and ovaries.