The nuclear orphan receptors COUP-TFII and Ear-2 act as silencers of the human oxytocin gene promoter

Abstract

We have previously shown that COUP-TFII and Ear-2, two members of the nuclear orphan receptor family, are able to repress oestrogen-stimulated transcriptional activity of the human oxytocin (OT) gene promoter by binding to a site that overlaps with the oestrogen response element (ERE) present in the 5 flanking region of the gene. Although most nuclear receptor-mediated transcriptional repression conforms with the paradigm of passive repression and involves competitive binding to an activator site, active repression, i.e. silencing of basal promoter activity, has been observed in a limited number of cases. Here we show by co-transfection experiments using COUP-TFII and Ear-2 expression vectors and reporter constructs containing OT gene promoter fragments linked to the chloramphenicol acetyltransferase gene that both COUP-TFII and Ear-2 are capable of silencing basal OT gene promoter activity by 54 and 75% respectively. 5 Deletion and footprint analyses revealed two areas of functionally important interaction sites: (1) a direct TGACC(T/C) repeat overlapping the ERE and (2) a more promoterproximal area centred at 90 containing three imperfect direct repeats (R1-R3) spaced by four nucleotides each. Mutagenesis of reporter constructs as well as electrophoretic mobility-shift assays demonstrated that each of the three proximal repeats R1-R3 contributed to orphan receptor binding and the silencing effect. Inasmuch as the orphan receptor-binding sites are not involved in mediating basal transcriptional activity of the OT gene promoter, the observed effects are best interpreted as active repression or promoter silencing. Moreover, since COUP-TFII and Ear-2 are both co-expressed in OT-expressing uterine epithelial cells, the novel transcriptional effects described here are likely to be of functional importance in the fine-tuning of uterine OT gene expression in vivo.

Genotyping-By-Sequencing (GBS) Detects Genetic Structure and Confirms Behavioral QTL in Tame and Aggressive Foxes (Vulpes vulpes)

“…COUP-TFII expression during embryonic development is significant for the development of forebrain and several other brain regions including amygdala [48–50]. It has been shown that COUP-TFII can also act as a silencer of the human oxytocin gene promoter in vitro [51]. COUP-TFII is an interesting candidate gene and its role in regulation of behavior in foxes will be further evaluated.…”

The Orphan Nuclear Receptor Ear-2 Is a Negative Coregulator for Thyroid Hormone Nuclear Receptor Function

“…Ear-2 binds to a site that overlaps the estrogen response element on the promoter region of the oxytocin gene (6,7).…”

Embryo-induced transcriptome changes in bovine endometrium reveal species-specific and common molecular markers of uterine receptivity

“…IFI16 protein is involved in the control of cell cycle regulation via modulation of TP53 (p53) and its target gene regulation (Kwak et al 2003). For NR2F2 (COUP-TFII), a nuclear orphan receptor, active repression of the human oxytocin gene promoter was shown in the uterine epithelial cells (Chu & Zingg 1997). In the mouse, NR2F2 haploinsufficiency results in decreased progesterone synthesis in the corpus luteum leading to reduced ability of the endometrium to support pregnancy (Takamoto et al 2005).…”