Molecular cloning and expression of rat placental lactogen-Iv, a variant of rPL-I present in late pregnant rat placenta.
Late pregnant rat placenta was found to contain a messenger RNA (mRNA) that encodes an additional member of the prolactin-growth hormone family. This polypeptide was detected by hybridization of complementary DNA (cDNA) for rPL-I to a 1 kilobase mRNA transcript in late pregnant rat placenta. A cDNA clone for the new polypeptide was isolated from a phage lambda-gt10 library containing cDNA synthesized from day 18 rat placental mRNA. Sequencing of the day 18 cDNA clone revealed that it was most closely related structurally to rPL-I and at the amino acid terminal was identical to the rPL-I variant (rPL-Iv). The sequence of rPL-Iv (223 amino acids) is 85% homologous to rPL-I (230 amino acid). There are 71 base pair changes (85% nucleotide homology) between rPL-Iv and rPL-I which are not confined to any specific region of the molecule and which result in 36 amino acid changes. In vitro translation of rPL-Iv mRNA produced by transcription of the cDNA template yielded a 26 kilodalton polypeptide, the size of the expected precursor protein. In situ hybridization studies indicated that mRNA for rPL-Iv was present primarily in cytotrophoblasts of the basal zone as early as day 15 of gestation with some hybridization in a few giant cells as well.
Department of Physiology, Faculty of Medicine, University of Manitoba, Winnipeg, Canada.
M C
MC
Robertson
I C
IC
Schroedter
H G
HG
Friesen
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D003001:Cloning, Molecular; D005260:Female; D008969:Molecular Sequence Data; D009693:Nucleic Acid Hybridization; D010920:Placenta / Q000378:metabolism*; D010928:Placental Lactogen / Q000235:genetics* / Q000378:metabolism; D011247:Pregnancy; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D013997:Time Factors; D014018:Tissue Distribution
D012333:RNA, Messenger; D010928:Placental Lactogen