DECIDUAL TROPHOBLAST PROLACTIN-RELATED PROTEIN - CHARACTERIZATION OF GENE STRUCTURE AND CELL-SPECIFIC EXPRESSION/

Decidual/trophoblast PRL-related protein (d/tPRP) is a member of the P RL gene family and is dually expressed in uterine and placental tissue s in a highly coordinated pattern during pregnancy. In the present stu dy, we describe the isolation and characterization of the d/tPRP gene. A lambda DASH II Wistar-Kyoto rat genomic library was screened with a labeled d/tPRP complementary DNA, resulting in the isolation of two p hage clones, RGLd-41 117.7 kilobases (kb)] and RGLd-42 (15.8 kb). RGLd -41 alone was found to contain the fulllength d/tPRP gene and was used for subsequent analyses. The d/tPRP gene possesses a six-exon, five-i ntron organization. Relative to other highly conserved members of the PRL gene family, d/tPRP contains a single small additional exon (exon 3) situated between exons 2 and 3 of the prototypical PRL gene. The re gion corresponding to exon 3 of d/tPRP encodes for a unique amino acid region found in a subset of PRL family members. A reverse transcripti on-PCR (RT-PCR) tissue survey for d/tPRP messenger RNA revealed that d /tPRP expression was restricted to decidual and trophoblast tissues. A single transcription start site 65 bp upstream of the initiation codo n was identified in decidual tissue, whereas multiple transcription st art sites ranging from 61-66 bp upstream of the initiation codon were detected in placental tissue. Various tissue culture systems (primary cultures and cell lines) were evaluated for d/tPRP expression and acti vation of a 3.96-kb d/tPRP promoter-luciferase reporter construct. Dec idual, spongiotrophoblast, and trophoblast giant cell populations expr essed d/tPRP and were capable of activating the d/tPRP promoter-report er construct, whereas other cell types were ineffective. Limited d/tPR P promoter activation was noted in uterine stromal cell lines. In summ ary, d/tPRP possesses a unique six-exon, five-intron gene structure an d exhibits cell-specific expression that is regulated at least in part by a 3.96-kb 6'-flanking region.