Characterization of the bovine prolactin gene

The gene coding for bovine prolactin was shown to exist as a single copy per haploid genome. Three restriction fragment polymorphisms were detected in the prolactin gene by Southern blot analysis of DNA obtained from the semen of pedigreed bulls representing eight breeds. The organization of the bovine prolactin gene was determined by restriction mapping of a clone isolated from a genomic library and by genomic blots. The 5'-flanking region and two exons were sequenced and the transcription start site mapped by primer extension. Comparison of the bovine prolactin sequence reported here with the published sequence of the rat prolactin gene revealed extensive homology (79%), extending 360 nucleotides upstream from the cap site, after which the sequences diverge. The homology exceeds that of the coding regions. A possible alternate intron-exon splice site was noted within the sequence coding for the signal peptide.