Multiple regulatory elements are required to direct trophoblast interferon gene expression in choriocarcinoma cells and trophectoderm.
Interferon-tau (IFN tau) is produced exclusively by the trophectoderm during the peri-implantation stage of pregnancy in ruminant ungulate species. Human choriocarcinoma cells (Jar) stably transfected with 1.8 kilobases of promoter from a bovine IFN tau gene ahead of a human GH (hGH) reporter gene constitutively synthesize hGH, but expression is not increased further by exposure to Newcastle disease virus. This and earlier experiments suggest that the transcriptional cues regulating IFN tau expression are distinct from those operating on other type I IFN genes. Transient transfection experiments reveal that two distinct promoter regions are required for full constitutive expression: one proximal (to position -126), which directs basal expression, and a more distal promoter region (positions -280 to -400), which acts as an enhancer. Nuclear extracts prepared from ovine conceptuses during the period of IFN tau expression interact with the proximal promoter region (positions -34 to -126) to form several complexes of high electrophoretic mobility. Although nucleotide sequence motifs potentially capable of binding the transcription factor IRF-1 are present in this region, IRF-1 does not transactivate the IFN tau gene. The distal part of the promoter contains only one region (-322 to -358) that forms a complex with these conceptus nuclear extracts. Both proximal and distal gel shift patterns become dramatically different when IFN tau gene expression ceases, perhaps reflecting the appearance of transcriptional repressors. Together these experiments support the conclusion that the control of IFN tau gene expression is very different from that of other type I IFN genes and that trophoblast-specific expression depends upon distal as well as proximal promoter regulatory elements.
Leaman
D W
DW
Department of Animal Sciences, University of Missouri, Columbia 65211.
Cross
J C
JC
Roberts
R M
RM
D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000494:pharmacology; D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D002417:Cattle / Q000196:embryology / Q000235:genetics / Q000378:metabolism; D002522:Chlorocebus aethiops; D002822:Choriocarcinoma / Q000473:pathology*; D016384:Consensus Sequence; D004268:DNA-Binding Proteins / Q000378:metabolism; D004475:Ectoderm / Q000378:metabolism*; D004742:Enhancer Elements, Genetic; D005260:Female; D005786:Gene Expression Regulation / Q000187:drug effects; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006801:Humans; D050856:Interferon Regulatory Factor-1; D050836:Interferon Regulatory Factor-2; D007370:Interferon Type I / Q000096:biosynthesis / Q000235:genetics; D007739:L Cells; D051379:Mice; D008969:Molecular Sequence Data; D009363:Neoplasm Proteins / Q000096:biosynthesis / Q000235:genetics; D009522:Newcastle disease virus / Q000502:physiology; D010750:Phosphoproteins / Q000378:metabolism; D011257:Pregnancy Proteins / Q000235:genetics*; D011401:Promoter Regions, Genetic; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis / Q000235:genetics; D012045:Regulatory Sequences, Nucleic Acid; D012097:Repressor Proteins; D016415:Sequence Alignment; D012689:Sequence Homology, Nucleic Acid; D012756:Sheep / Q000196:embryology; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014157:Transcription Factors / Q000378:metabolism; D014162:Transfection; D014212:Tretinoin / Q000494:pharmacology; D014327:Trophoblasts / Q000378:metabolism*; D014407:Tumor Cells, Cultured; D014594:Uterine Neoplasms / Q000473:pathology*
D004268:DNA-Binding Proteins; C494257:IRF1 protein, human; C494229:IRF2 protein, human; D050856:Interferon Regulatory Factor-1; D050836:Interferon Regulatory Factor-2; D007370:Interferon Type I; C494258:Irf1 protein, mouse; C494230:Irf2 protein, mouse; D009363:Neoplasm Proteins; D010750:Phosphoproteins; D011257:Pregnancy Proteins; D011993:Recombinant Fusion Proteins; D012097:Repressor Proteins; D014157:Transcription Factors; C063743:interferon omega 1; C020947:interferon tau; D015124:8-Bromo Cyclic Adenosine Monophosphate; D014212:Tretinoin; D013755:Tetradecanoylphorbol Acetate