Molecular cloning of a prolactin-related mRNA expressed in bovine placenta

Bovine (Bos taurus) prolactin-related cDNA I (bPRC-I), distinct from the isolated bovine placental lactogen, was derived from bovine fetal placental mRNA by molecular cloning. The nucleotide sequence is 63% homologous to bovine prolactin cDNA and only 45% to bovine growth hormone. The region of bPRC-I corresponding to the 5' portion of the signal peptide and 5' untranslated region of bovine prolactin mRNA is markedly different from prolactin. The predicted protein is 39% homologous to bovine prolactin and about 30% to the related placental hormones in rodents. This identification of a prolactin-related gene in the cow in addition to those reported in rodents suggests that multiple prolactin-related genes expressed in the placenta may be a general phenomenon in nonprimates. The role of these related hormones during gestation remains to be investigated.