CLONING OF A NOVEL RAT PLACENTAL PROLACTIN-LIKE PROTEIN C-RELATED CDNA

Prolactin-like protein C (PLP-C) is a major rat placental protein whic h is expressed during the second half of pregnancy and belongs to the growth hormone-prolactin family. Here we report on the isolation of ov erlapping rat placental cDNAs which specify a transcript of 915 base p airs and predict a 205-amino acid translated product. The full-length cDNA shares 93% homology with the nucleotide sequence reported for PLP -C, and the putative protein, which we designate PCRP (prolactin-like protein C-related protein), exhibits 88% homology with the PLP-C precu rsor protein. PCRP lacks the signal sequence and the first 2 N-termina l cysteine residues present in PLP-C. Northern blot analysis indicated the basal zone-specific expression of PCRP mRNA, with no detectable e xpression in decidua and labyrinth. Southern blot analysis of rat geno mic DNA using PCRP cDNA as a probe demonstrated multiple hybridization bands, suggestive of a family of genes encoding prolactin-like protei ns. Western immunoblot analysis of basal zone culture media using a PC RP antipeptide antiserum revealed at least 5 immunoreactive proteins. The existence of a PLP-C family of proteins in rat placenta after midp regnancy suggests their functional sig nificance in the maintenance of pregnancy and fetal development. (C) 1995 Wiley Liss, Inc.