431 MOLECULAR CLONING OF DNA COMPLEMENTARY TO BOVINE PROLACTIN MESSENGER RNA

Abstract

Prolactin (PRL), growth hormone (GH) and chorionic sommatammotropin form a family of protein hormones derived from a common evolutionary ancestor. To facilitate study of the structure,regulation, and evolution of this set of related genes, we have previously cloned complementary DNA (cDNA) for bovine GH (J. Biol. Chem. 255:7521). We now report the cloning of cDNA to bovine PRL. A previously cloned bPRL cDNA fragment (Endocrinology 107:851) was labeled with 32P by nick-translation and used to identify clones containing bPRL sequences. All clones were originally derived from bovine pituitary cDNA cloned in the PstI site of pBR322 by the dC.dG tailing technique. One of these clones contained cDNA corresponding to all 199 AA's of bPRL, plus 10 AA's from the pre-sequence and 75 Bases from the 3′untranslated region. The sequence of the entire 702 nucleotides was determined and compared to the sequence of rat and human PRL cDNA's. The bPRL cDNA sequence permitted identification of 10 AA's in the pre-sequence and of 16 AA's where glutamic and aspartic acids had not been differentiated from their amides by AA sequencing. The homology between bPRL and rat PRL is 60.5% for the AA sequence and 70.8% for the nucleotide sequence. The corresponding values for a comparison of bPRL and human PRL are 74.0 and 79.7%, respectively. 59.5% of bPRL codons end in G or C, whereas this value is 81.7% for bGH. Such codon choice appears to be a characteristic difference between GH and PRL genes.

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