title: Identification, characterization, and expression of a new prolactin-like molecule in the hamster placenta.
abstract: In the hamster, serum total lactogenic activity increases during the latter half of gestation (Days 8-16). On Days 10 and 12 a substantial amount of lactogenic activity cannot be attributed to prolactin (PRL) and hamster placental lactogen-II (haPL-II); therefore, the presence of a molecule similar to placental lactogen-I (PL-I), as found in the rat and mouse at midpregnancy, has been hypothesized for the hamster. The objectives of this study were to identify PRL-like molecules synthesized by the hamster placenta and to determine the temporal and cellular synthesis of identified molecules. Oligonucleotides (20-23 bp) corresponding to regions of nucleotide homology between mouse PL-I (mPL-I) and rat PL-I (rPL-I) along with midgestation hamster placental RNA were used in 3' rapid amplification of cDNA ends (RACE) methodology to generate PRL-like cDNA. A 444-bp cDNA fragment that had nucleotide sequence similarity with members of the prolactin-growth hormone (PRL-GH) gene family was generated. This cDNA fragment was utilized to screen a Day 16 hamster placental bacteriophage cDNA library, and a clone containing the entire coding region was identified and sequenced. The molecule had 77% nucleotide sequence homology with mouse proliferin-related protein (mPRP) and somewhat less homology (approximately 60%) with hamster, rat, and mouse PRL or placental lactogens (PL). The derived amino acid sequence of the identified molecule contained a 15-residue signal sequence and a 219-residue peptide with a calculated molecular weight of 25477. The peptide shared 58% amino acid sequence identity with mPRP. Placental expression of the PRL-like molecule during the latter half of gestation was evaluated by Northern and slot-blot analyses using the 444-bp cDNA fragment as a hybridization probe. A 1-kb transcript was detected on Days 9-15 with peak expression on Days 10 and 11. Messenger RNA for the PRL-like molecule was localized to cytotrophoblast but not giant trophoblast cells of the placental trophospongium region. In addition, specific immunostaining using an antibody to mPRP was confined to cytotrophoblast cells.
authors.affiliation: Department of Anatomy and Cell Biology, East Carolina University School of Medicine, Greenville, North Carolina 27858, USA.
authors.forename: S W
authors.initials: SW
authors.lastname: Barnes
authors.forename: R H
authors.initials: RH
authors.lastname: Renegar
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D015152:Blotting, Northern; D006224:Cricetinae; D018076:DNA, Complementary / Q000737:chemistry / Q000302:isolation & purification; D005260:Female; D015870:Gene Expression; D008647:Mesocricetus; D051379:Mice; D008969:Molecular Sequence Data; D010920:Placenta / Q000737:chemistry*; D010928:Placental Lactogen / Q000032:analysis / Q000235:genetics; D016133:Polymerase Chain Reaction; D011247:Pregnancy; D011257:Pregnancy Proteins / Q000737:chemistry; D011388:Prolactin / Q000032:analysis* / Q000737:chemistry / Q000235:genetics*; D051381:Rats; D016415:Sequence Alignment
chemical_list: D018076:DNA, Complementary; C057074:Plfr protein, mouse; D011257:Pregnancy Proteins; C489178:Prl7d1 protein, rat; C085699:placental lactogen I, rat; D011388:Prolactin; D010928:Placental Lactogen