title: Immortalization of virus-free human placental cells that express tissue-specific functions.
abstract: Human pregnancy-specific glycoproteins (PSGs) are a family of closely related placental proteins that, together with the carcinoembryonic antigen members, comprise a subfamily within the immunoglobulin superfamily. To facilitate study of the control of PSG expression, we immortalized human placental cell lines with adenovirus-origin-minus (ori-)-simian virus-40 (SV40) recombinant viruses containing either wild-type or temperature-sensitive (ts) A mutants of SV40. Cells transformed with the SV40 tsA chimera (HP-A1 and HP-A2), but not the SV40 wild-type chimera (HP-W1), were temperature sensitive for transformation. All three cell lines expressed trophoblast-specific genes, including PSG and the alpha- and beta-subunits of hCG. Human CG alpha expression was greatly stimulated by (Bu)2cAMP in all three cell lines; shifting HP-A1 and HP-A2 cells to the nonpermissive temperature (39.5 C) further increased hCG alpha expression. At both 33 C (permissive temperature) and 39.5 C, the transformed placental cells expressed PSG mRNAs of 2.2 and 1.7 kilobases; expression was greatly stimulated by sodium butyrate. In the absence of an inducer, the three placental lines synthesized a PSG of 64 kilodaltons (kDa). In the presence of butyrate, they synthesized PSGs of 72, 64, and 54 kDa, similar to the placental PSGs. However, in placenta the predominant species is the 72-kDa product. At 39.5 C, butyrate selectively increased synthesis of the 72-kDa PSG in HP-A1 and HP-A2 cells. To characterize PSG promoter activity, we constructed chloramphenicol acetyltransferase (CAT) fusion genes containing -809 to -44 basepairs up-stream of the translational start site of the PSG6 gene. Using transient expression assays, we demonstrated that the -809/-44 region of the PSG6 gene contained cis-acting sequences that can direct CAT expression in human placental cells. Sodium butyrate, which stimulates PSG expression, greatly increased CAT activity, indicating that butyrate-induced PSG expression is regulated primarily at the level of gene transcription.
authors.affiliation: Human Genetics Branch, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892.
authors.forename: K J
authors.initials: KJ
authors.lastname: Lei
authors.forename: Y
authors.initials: Y
authors.lastname: Gluzman
authors.forename: C J
authors.initials: CJ
authors.lastname: Pan
authors.forename: J Y
authors.initials: JY
authors.lastname: Chou
mesh_terms: D001483:Base Sequence; D002087:Butyrates / Q000494:pharmacology; D020148:Butyric Acid; D002461:Cell Line, Transformed / Q000378:metabolism*; D006063:Chorionic Gonadotropin / Q000096:biosynthesis; D015870:Gene Expression / Q000187:drug effects; D006680:HLA Antigens / Q000096:biosynthesis; D006801:Humans; D007150:Immunohistochemistry; D008969:Molecular Sequence Data; D010920:Placenta / Q000378:metabolism*; D011257:Pregnancy Proteins / Q000096:biosynthesis* / Q000235:genetics; D011268:Pregnancy-Specific beta 1-Glycoproteins; D011401:Promoter Regions, Genetic; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis; D013539:Simian virus 40
chemical_list: D002087:Butyrates; D006063:Chorionic Gonadotropin; D006680:HLA Antigens; C075077:PSG6 protein, human; D011257:Pregnancy Proteins; D011268:Pregnancy-Specific beta 1-Glycoproteins; D011993:Recombinant Fusion Proteins; D020148:Butyric Acid