Multiple phosphorylation events control chicken ovalbumin upstream promoter transcription factor I orphan nuclear receptor activity.
Chicken ovalbumin upstream promoter transcription factor I (COUP-TFI) is an orphan member of the nuclear hormone receptor superfamily that comprises key regulators of many biological functions, such as embryonic development, metabolism, homeostasis, and reproduction. Although COUP-TFI can both actively silence gene transcription and antagonize the functions of various other nuclear receptors, the COUP-TFI orphan receptor also acts as a transcriptional activator in certain contexts. Moreover, COUP-TFI has recently been shown to serve as an accessory factor for some ligand-bound nuclear receptors, suggesting that it may modulate, both negatively and positively, a wide range of hormonal responses. In the absence of any identified cognate ligand, the mechanisms involved in the regulation of COUP-TFI activity remain unclear. The elucidation of several putative phosphorylation sites for MAPKs, PKC, and casein kinase II within the sequence of this orphan receptor led us to investigate phosphorylation events regulating the various COUP-TFI functions. After showing that COUP-TFI is phosphorylated in vivo, we provide evidence that in vivo inhibition of either MAPK or PKC signaling pathway leads to a specific and pronounced decrease in COUP-TFI-dependent transcriptional activation of the vitronectin gene promoter. Focusing on the molecular mechanisms underlying the MAPK- and PKC-mediated regulation of COUP-TFI activity, we show that COUP-TFI can be directly targeted by PKC and MAPK. These phosphorylation events differentially modulate COUP-TFI functions: PKC-mediated phosphorylation enhances COUP-TFI affinity for DNA and MAPK-mediated phosphorylation positively regulates the transactivation function of COUP-TFI, possibly through enhancing specific coactivator recruitment. These data provide evidence that COUP-TFI is likely to integrate distinct signaling pathways and raise the possibility that multiple extracellular signals influence biological processes controlled by COUP-TFI.
Gay
Frédérique
F
Equipe Information et Programmation Cellulaire, Unité Mixte de Recherche 6026 Centre National de la Recherche Scientifique, Université de Rennes I, Campus de Beaulieu, 35042 Rennes Cedex, France.
Baráth
Peter
P
Desbois-Le Péron
Christine
C
Métivier
Raphaël
R
Le Guével
Rémy
R
Birse
Darcy
D
Salbert
Gilles
G
D000818:Animals; D001483:Base Sequence; D019556:COS Cells; D051838:COUP Transcription Factor I; D002645:Chickens / Q000235:genetics*; D016384:Consensus Sequence; D004247:DNA / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000378:metabolism*; D024202:Electrophoretic Mobility Shift Assay; D006801:Humans; D020935:MAP Kinase Signaling System; D051379:Mice; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D010766:Phosphorylation; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding; D011493:Protein Kinase C / Q000378:metabolism; D018160:Receptors, Cytoplasmic and Nuclear / Q000737:chemistry / Q000378:metabolism*; D011965:Receptors, Glucocorticoid / Q000737:chemistry / Q000378:metabolism; D020218:Response Elements / Q000235:genetics; D014157:Transcription Factors / Q000737:chemistry / Q000378:metabolism*; D014158:Transcription, Genetic / Q000235:genetics; D015533:Transcriptional Activation; D019096:Vitronectin / Q000235:genetics
D051838:COUP Transcription Factor I; D004268:DNA-Binding Proteins; C497589:NR2F1 protein, human; C497590:Nr2f1 protein, mouse; D018160:Receptors, Cytoplasmic and Nuclear; D011965:Receptors, Glucocorticoid; D014157:Transcription Factors; D019096:Vitronectin; D004247:DNA; D011493:Protein Kinase C; D020928:Mitogen-Activated Protein Kinases