Cloning, Expression and Regulation of Chicken Ovalbumin Upstream Promoter Transcription Factors (COUP-TFII and EAR-2) in the Rat Anterior Pituitary Gland

Abstract

Chicken ovalbumin upstream promoter transcription factors (COUP-TF)-II (NR2F2) and EAR-2 (NR2F6) are structurally related orphan members of the nuclear receptors superfamily. There are growing evidences that these factors play important roles during processes of differentiation and proliferation of several tissues. To better understand their role in the differentiated adult rat pituitary gland, we cloned COUP-TFII and EAR-2 cDNAs from an anterior pituitary cDNA library. Subsequently, we raised and characterized specific antibodies to the N-terminal domain of both nuclear receptors. We next examined their cellular and subcellular distribution in the pituitary gland and determined their regulation during pregnancy. COUP-TFII and EAR-2 pituitary genes display, respectively, 90 and 100% homologies with their human and mouse homologues. Cellular expression of both nuclear receptors was mainly detected in the lactotropes of male and female rats, with a prominent distribution in the nuclear compartment for EAR-2, and interestingly both proteins were significantly upregulated in pituitaries of pregnant vs. cycling female rats. Thus, our results have characterized cloning of rat pituitary COUP-TFII and EAR-2 genes, demonstrated that they are both specifically expressed in lactotropes, and strongly suggested that they may play an important role in modulating prolactin (PRL) gene expression during pregnancy.

Seven‐up facilitates insect counter‐defense by suppressing cathepsin B expression

“…The Drosophila Seven‐up ( Svp ) gene, encoding the COUP‐TF ortholog, determines photoreceptor cell fate [19], controls cell proliferation in Malpighian tubules [20], and inhibits ecdysone‐dependent transcription [18]. Important roles of COUP‐TF/Svp in neurogenesis, organogenesis and embryogenesis have been illustrated in mammals, chicken, zebrafish, frog and insects [12,14,18,21–23]. More recently, its involvement in regulating mobilization and utilization of glycogen and lipid in skeletal muscle cells has been reported [24–26].…”

Nuclear Receptors as Regulators of Pituitary Corticotroph Pro-Opiomelanocortin Transcription

“…Chicken ovalbumin upstream promoter transcription factors (COUP-TFs) are highly conserved across species [149] and bind promiscuously to a wide range of direct GGTCA repeat with different spacing and orientations, repressing gene expression either by active repression or by competition for binding sites of other transcription factor [46,150]. COUP-TFα is highly expressed in neuronal tissues of the central and peripheral nervous systems, whereas COUP-TFβ is mainly expressed during embryonic development to regulate neural, muscular, bone, liver and skin differentiation [151].…”

“…COUP-TFα is highly expressed in neuronal tissues of the central and peripheral nervous systems, whereas COUP-TFβ is mainly expressed during embryonic development to regulate neural, muscular, bone, liver and skin differentiation [151]. COU-TFs have lineage-restricted distribution in the normal pituitary, with COUP-TFα expressed exclusively in normal corticotrophs, whereas COUP-TFβ and COUP-TFγ are expressed predominantly in lactotrophs [149]. In contrast, human corticotroph tumors did not express COUP-TFα, suggesting a possible role for COUP-TFα in dysregulated corticotroph cells [45].…”

“…Using a highly conserved half-site nuclear receptor binding element (NRBE, AAA ACC CC) present in nPE2, de Souza et al performed yeast one-hybrid screening of an adult mouse brain cDNA library and identified ERα (also known as ESR1) as a potential transcriptional regulator of hypothalamic POMC, suggesting that estrogen exerts its anorectic effect by controlling neuronal POMC expression [152] (Table 1). Chicken ovalbumin upstream promoter transcription factors (COUP-TFs) are highly conserved across species [149] and bind promiscuously to a wide range of direct GGTCA repeat with different spacing and orientations, repressing gene expression either by active repression or by competition for binding sites of other transcription factor [46,150]. COUP-TFα is highly expressed in neuronal tissues of the central and peripheral nervous systems, whereas COUP-TFβ is mainly expressed during embryonic development to regulate neural, muscular, bone, liver and skin differentiation [151].…”

Gonadotropin-Releasing Hormone and Gonadal Steroids Regulate Transcription Factor mRNA Expression in Primary Pituitary and Immortalized Gonadotrope Cells

“…Within the anterior pituitary gland, COUP-TFI has been detected in the gonadotrope and somatotrope cells, with COUP-TFII expression in the gonadotropes and lactotropes. 41,42 Although they most commonly inhibit promoter activity, they may also stimulate gene expression depending on promoter and cellular context. [43][44][45] Supporting the functional importance of these factors in the gonadotrope, we have reported that siRNA-mediated decreases in endogenous COUP-TFI or COUP-TFII expression blunt a-subunit, LHb-, FSHb-, and GnRHR messenger RNA (mRNA) levels in the LbT2 cell line.…”