Molecular cloning and nucleotide sequence of DNA complementary to human decidual prolactin mRNA.

Three human decidual prolactin (PRL) cDNA clones (pdPL-1:349 base pairs, pdPL-2:584 base pairs, pdPL-3:807 base pairs without poly(A) tract) were prepared and sequenced. The insert DNA of the largest clone pdPL-3 contained the coding region corresponding to 217 amino acid residues including 18 amino acid residues of the signal peptide, and 157 nucleotides of the 3'-untranslated region. A comparison of the pdPL-3 cDNA sequence with that of human pituitary PRL cDNA revealed 4 silent nucleotide differences. Two of the base changes occurred in the third position of the amino acid codons, and the other two occurred in the 3'-untranslated region. Therefore, the amino acid sequence of decidual PRL deduced from the nucleotide sequence of pdPL-3 was identical with that of pituitary PRL. Minor changes were also observed among the three PRL mRNAs: a silent change in the third codon in the translated region, and another change in the 3'-untranslated region. Southern blot hybridization of human cellular DNA with the pdPL-3 probe indicates that PRL gene may occur once per haploid genome. Therefore, these minor changes may reflect microheterogeneity of PRL gene. The existence of multiple poly(A)-adjacent sequences was shown in the three species of human decidual PRL mRNA and in human pituitary PRL mRNA. This variation may be due to heterogeneity in the processing at the 3' terminus of mRNA or the termination sites of the transcription.