Abstract
Prolactin (Prl), growth hormone, and chorionic sommatomammotropin form a set (the "Prl set") of hormones which is thought to have evolved from a common ancestral gene. This assumption is based on several lines of evidence: overlap in their biological and immunological properties, similarities in their amino acid sequences, and homologies in the nucleic acid sequences of their structural genes. In the current study we report the cloning, amplification in bacteria, and sequence analysis of DNA complementary to Prl mRNA isolated from human pituitary Prl-secreting adenomas. The cloned DNA contains 914 bases, which includes the entire coding sequence of human prePrl as well as portions of the 5- and 3'-untranslated regions of the mRNA. The amino acid sequence predicted by our data differs from a previously reported amino acid sequence in 8 positions. With the results of this study we can now compare in one species the nucleotide sequences of the structural gene coding for each of the hormones of the Prl set. The sequence divergence at replacement sites is used to establish an evolutionary clock for the Prl set of genes. Using this clock, we postulate that the chromosomal segregation of human Prl and human growth hormone occurred about 392 million years ago and that growth hormone and chorionic sommatomammotropin underwent an intrachromosomal recombination within the last 10 million years.
Highlights
Prolactin (Prl), growth hormone, and chorionic som- Nilson et aL, 1980)have given considerable additional support matomammotropin form a set of hor- to thehypothesis of common ancestry
This cloned hPrl cDNA should be useful as a probe to map and differs from a previously reported amino acid sequeniscoelate the corresponding hPrl genomic sequences, to deterin 8 positions.With theresults of this study we can mine the chromosomal location of the Prlgene (Owerbach et compare in onespecies the nucleotide sequencesof the al., 1980b),to synthesize hPrl in bacteria,:’and to study the structural gene coding for eachof the hormonesof the regulation of Prl gene expression
The band at 26,000 daltons was immunoprecipitated by antibody to hPr1 (Fig. 1B). This band was not precipitated by antisera to hGH or by normal rabbit serum, indicating that the predominant protein produced by the polyadenylated RNA from these pituitary tumors was human prePr1
Summary
Prolactin (Prl), growth hormone, and chorionic som- Nilson et aL, 1980)have given considerable additional support matomammotropin form a set (the “Prl set”) of hor- to thehypothesis of common ancestry. A strand of dCMPs was added to the3"ends of the cDNA, Plasmid DNA wasisolated from each of these colonies, and it was annealed to pBR322 which had been previ- cleaved with Pst I, and analyzed by gel electrophoresis.
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