CLONING OF A CDNA-ENCODING BOVINE ERYTHROPOIETIN AND ANALYSIS OF ITS TRANSCRIPTION IN SELECTED TISSUES

A bovine cDNA encoding erythropoietin (Epo) was isolated by polymerase chain reaction (PCR) amplification and screening of a bovine kidney c DNA library. The sequenced cDNA has a length of 1312 bp and an open re ading frame that encodes a predicted 192-amino-acid (aa) protein, incl uding a putative signal sequence of 25 aa. A mature protein of 167 aa (18.4 kDa) results upon cleavage of the putative signal peptide. The d educed bovine mature Epo peptide exhibits 96, 88, 83, 82 and 79% seque nce identity to that of sheep, swine, human, monkey and rat, respectiv ely. The expression of the bovine Epo gene in tissues from a severely anemic calf, bovine fetus and a healthy steer was analysed by a compet itive RT-PCR method. In kidneys of the severely anemic calf, Epo mRNA levels increased 60-fold relative to that from the kidneys of the heal thy steer. Epo mRNA levels were threefold higher in the liver of the b ovine fetus than that in its kidneys. Low levels of Epo transcripts we re detected in RNA from spleen of the severely anemic calf and the bov ine fetus. No Epo transcripts were detectable in spleen from the healt hy steer.