• BMB Reports
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• v.47 no.9
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• pp.518-523
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• 2014

The maternal transcription factor Dorsal (Dl) functions as both an activator and a repressor in a context-dependent manner to control dorsal-ventral patterning in the Drosophila embryo. Previous studies have suggested that Dl is an intrinsic activator and its repressive activity requires additional corepressors that bind corepressor-binding sites near Dl-binding sites. However, the molecular identities of the corepressors have yet to be identified. Here, we present evidence that Capicua (Cic) is involved in Dl-mediated repression in the zerkn$\ddot{u}$llt (zen) ventral repression element (VRE). Computational and genetic analyses indicate that a DNA-binding consensus sequence of Cic is highly analogous with previously identified corepressor-binding sequences and that Dl failed to repress zen expression in lateral regions of cic mutant embryos. Furthermore, electrophoretic mobility shift assay (EMSA) shows that Cic directly interacts with several corepressor-binding sites in the zen VRE. These results suggest that Cic may function as a corepressor by binding the VRE.

• Molecules and Cells
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• v.41 no.9
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• pp.842-852
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• 2018

Notch signaling is an evolutionarily conserved pathway and involves in the regulation of various cellular and developmental processes. Ligand binding releases the intracellular domain of Notch receptor (NICD), which interacts with DNA-bound CSL [CBF1/Su(H)/Lag-1] to activate transcription of target genes. In the absence of NICD binding, CSL down-regulates target gene expression through the recruitment of various corepressor proteins including SMRT/NCoR (silencing mediator of retinoid and thyroid receptors/nuclear receptor corepressor), SHARP (SMRT/HDAC1-associated repressor protein), and KyoT2. Structural and functional studies revealed the molecular basis of these interactions, in which NICD coactivator and corepressor proteins competitively bind to ${\beta}-trefoil$ domain (BTD) of CSL using a conserved ${\varphi}W{\varphi}P$ motif (${\varphi}$ denotes any hydrophobic residues). To date, there are conflicting ideas regarding the molecular mechanism of SMRT-mediated repression of CSL as to whether CSL-SMRT interaction is direct or indirect (via the bridge factor SHARP). To solve this issue, we mapped the CSL-binding region of SMRT and employed a 'one- plus two-hybrid system' to obtain CSL interaction-defective mutants for this region. We identified the CSL-interaction module of SMRT (CIMS; amino acid 1816-1846) as the molecular determinant of its direct interaction with CSL. Notably, CIMS contains a canonical ${\varphi}W{\varphi}P$ sequence (APIWRP, amino acids 1832-1837) and directly interacts with CSL-BTD in a mode similar to other BTD-binding corepressors. Finally, we showed that CSL-interaction motif, rather than SHARP-interaction motif, of SMRT is involved in transcriptional repression of NICD in a cell-based assay. These results strongly suggest that SMRT participates in CSL-mediated repression via direct binding to CSL.

• Proceedings of the Korean Society of Applied Entomolohy Conference
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• 2002.11a
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• pp.28-28
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• 2002

• Journal of the Korean Magnetic Resonance Society
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• v.2 no.1
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• pp.33-40
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• 1998

The cross peak intensities versus mixing times of 2D NOESY spectrum for a corepressor L-trp were simulated for the case of a ligand exchanging between free (AX) and bound (A'X') forms in protein/DNA complex. The direct NOE (I(AX)) of the free ligand exhibited a small positive intensity indicative of the strong dominant influence of the bound ligand. The exchange-mediated NOE peak (I(AX')) was very sensitive to corepressor exchange. However, both diagonal (I(A'A')) and direct NOE (I(A'X')) intensities of the bound ligand were not affected much at initial stage. Both peaks were severely influenced by exchange at mixing times of greater than 100 ms. In conclusion, since the NOE intensity is a function of exchange rate, the exchange effect should be considered to properly extract accurate distance information for bound ligand in the presence of conformational exchange.

• Genomics & Informatics
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• v.9 no.3
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• pp.93-101
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• 2011

The Hairless (HR ) gene regulates the expression of several target genes as a transcriptional corepressor of nuclear receptors. The hair follicle (HF), a small independent organ of the skin, resides in the epidermis and undergoes regenerative cycling for normal hair formation. HF development requires many genes and signaling pathways to function properly in time and space, one of them being the HR gene. Various mutations of the HR gene have been reported to cause the hair loss pheno-type in rodents and humans. In recent studies, it has been suggested that the HR gene is a critical player in the regulation of the hair cycle and, thus, HF development. Furthermore, the HR gene is associated with the Wnt signaling pathway, which regulates proliferation and differentiation of cells and plays an essential role in hair and skin development. In this review, we summarize the mutations responsible for human hair disorders and discuss the roles of the HR gene in HF development.

• Journal of Life Science
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• v.28 no.7
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• pp.765-771
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• 2018

Peroxisome proliferator-activated receptor gamma ($PPAR{\gamma}$) is a key transcription factor that regulates adipogenesis, and epigenetic control of $PPAR{\gamma}$ is of great interest in obesity-inhibition research. Our previous study showed that CACUL1 (CDK2-associated cullin domain 1) acts as a corepressor that inhibits $PPAR{\gamma}$ transcriptional activity and adipocyte differentiation. Here, we investigated the roles of protein arginine methyltransferase 5 (PRMT5), a novel binding partner of CACUL1, in regulating $PPAR{\gamma}$. The interaction between PRMT5 and CACUL1 was shown by immunoprecipitation assay in vivo and GST pulldown assay in vitro. As shown by luciferase reporter assay, PRMT5 and CACUL1 cooperated to inhibit the transcriptional activity of $PPAR{\gamma}$. The suppressive role of PRMT5 in adipogenesis was examined by Oil Red O staining using 3T3-L1 cells, which stably overexpress or deplete PRMT5. Overexpression of PRMT5 suppresses $PPAR{\gamma}$-mediated adipogenesis, whereas PRMT5 knockdown increases lipid accumulation in 3T3-L1 cells. Consistently, PRMT5 attenuates the expression of Lpl and aP2, the target genes of $PPAR{\gamma}$, as demonstrated by RT-qPCR analysis. Overall, these results suggest that PRMT5 interacts with CACUL1 to impair the transcriptional activity of $PPAR{\gamma}$, leading to the inhibition of adipocyte differentiation. Therefore, the regulation of PRMT5 enzymatic activity may provide a clue to develop an anti-obesity drug.

• Molecules and Cells
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• v.44 no.1
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• pp.1-12
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• 2021

The nuclear receptor peroxisome proliferator-activated receptor γ (PPARγ) is the master transcriptional regulator in adipogenesis. PPARγ forms a heterodimer with another nuclear receptor, retinoid X receptor (RXR), to form an active transcriptional complex, and their transcriptional activity is tightly regulated by the association with either coactivators or corepressors. In this study, we identified T-cell death-associated gene 51 (TDAG51) as a novel corepressor of PPARγ-mediated transcriptional regulation. We showed that TDAG51 expression is abundantly maintained in the early stage of adipogenic differentiation. Forced expression of TDAG51 inhibited adipocyte differentiation in 3T3-L1 cells. We found that TDAG51 physically interacts with PPARγ in a ligand-independent manner. In deletion mutant analyses, large portions of the TDAG51 domains, including the pleckstrin homology-like, glutamine repeat and proline-glutamine repeat domains but not the proline-histidine repeat domain, are involved in the interaction with the region between residues 140 and 506, including the DNA binding domain, hinge, ligand binding domain and activation function-2 domain, in PPARγ. The heterodimer formation of PPARγ-RXRα was competitively inhibited in a ligand-independent manner by TDAG51 binding to PPARγ. Thus, our data suggest that TDAG51, which could determine adipogenic cell fate, acts as a novel negative regulator of PPARγ by blocking RXRα recruitment to the PPARγ-RXRα heterodimer complex in adipogenesis.

• Journal of Ginseng Research
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• v.48 no.1
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• pp.89-97
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• 2024

Background: Ginsenoside F2 (GF2), the protopanaxadiol-type constituent in Panax ginseng, has been reported to attenuate metabolic dysfunction-associated steatotic liver disease (MASLD). However, the mechanism of action is not fully understood. Here, this study investigates the molecular mechanism by which GF2 regulates MASLD progression through liver X receptor (LXR). Methods: To demonstrate the effect of GF2 on LXR activity, computational modeling of protein-ligand binding, Time-resolved fluorescence resonance energy transfer (TR-FRET) assay for LXR cofactor recruitment, and luciferase reporter assay were performed. LXR agonist T0901317 was used for LXR activation in hepatocytes and macrophages. MASLD was induced by high-fat diet (HFD) feeding with or without GF2 administration in WT and LXRα^-/- mice. Results: Computational modeling showed that GF2 had a high affinity with LXRα. LXRE-luciferase reporter assay with amino acid substitution at the predicted ligand binding site revealed that the S264 residue of LXRα was the crucial interaction site of GF2. TR-FRET assay demonstrated that GF2 suppressed LXRα activity by favoring the binding of corepressors to LXRα while inhibiting the accessibility of coactivators. In vitro, GF2 treatments reduced T0901317-induced fat accumulation and pro-inflammatory cytokine expression in hepatocytes and macrophages, respectively. Consistently, GF2 administration ameliorated hepatic steatohepatitis and improved glucose or insulin tolerance in WT but not in LXRα^-/- mice. Conclusion: GF2 alters the binding affinities of LXRα coregulators, thereby interrupting hepatic steatosis and inflammation in macrophages. Therefore, we propose that GF2 might be a potential therapeutic agent for the intervention in patients with MASLD.

• Journal of Life Science
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• v.30 no.2
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• pp.211-220
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• 2020

The activity of CAR can be regulated not only by ligand binding but also by phosphorylation of regulatory factors involved in extracellular signaling pathways, cross-talk interactions with transcription factors, and the recruitment, degradation, and expression of coactivators and corepressors. This regulation of CAR activity can in turn have effects on the control of diverse physiological homeostasis, including xenobiotic and energy metabolism, cellular proliferation, and apoptosis. CAR is phosphorylated by the ERK1/2 signaling pathway, which causes formation of a complex with Hsp-90 and CCRP, leading to its cytoplasmic retention, whereas phenobarbital inhibits ERK1/2, which causes dephosphorylation of the downstream signaling molecules, leading to the recruitment to CAR of the activated RACK-1/PP2A components for the dephosphorylation, nuclear translocation, and the transcriptional activation of CAR. Activated CAR cross-talks with FoxO1 to induce inhibition of its transcriptional activity and with PGC-1α to induce protein degradation by ubiquitination, resulting in the transcriptional suppression of PEPCK and G6Pase involved in gluconeogenesis. Regulation by CAR of lipid synthesis and oxidation is achieved by its functional cross-talks, respectively, with PPARγ through the degradation of PGC-1α to inhibit expression of the lipogenic genes and with PPARα through either the suppression of CPT-1 expression or the interaction with PGC-1α each to induce tissue-specific inhibition or stimulation of β-oxidation. Whereas CAR stimulates cellular proliferation by suppressing p21 expression through the inhibition of FoxO1 transcriptional activity and inducing cyclin D1 expression, it suppresses apoptosis by inhibiting the activities of MKK7 and JNK-1 through the expression of GADD45B. In conclusion, CAR is involved in the maintenance of homeostasis by regulating not only xenobiotic metabolism but also energy metabolism, cellular proliferation, and apoptosis through diverse cross-talk interactions with extracellular signaling pathways and intracellular regulatory factors.

• Journal of Life Science
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• v.21 no.2
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• pp.242-250
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• 2011

Although insulin-like growth factor-I (IGF-I) and androgen receptor (AR) coactivators are well known effectors of skeletal muscle, the molecular mechanism by which signaling pathways integrating AR coactivators and IGF-I in skeletal muscle cells has not been previously examined. In this study, the effects of IGF-I treatment on the gene expression of AR coactivators in the absence of AR ligands and the roles of the p38 MAPK and ERK1/2 signaling pathways in IGF-I-induced AR coactivators induction were examined. C2C12 cells were treated with 250 ng/ml of IGF-I in the presence or absence of specific inhibitors p38 MAPK (SB203580) or ERK1/2 (PD98059). Treatment of C2C12 cells with IGF-I resulted in increased in GRIP-1, SRC-1, and ARA70 protein expression. The levels of GRIP-1, SRC-1, and ARA70 mRNA were also significantly increased after 5min of IGF-I treatment. IGF-I-induced AR coactivator proteins were significantly blocked by pharmacological inhibitors of p38 MAPK and ERK1/2 pathways. However, there was no significant effect of those inhibitors on IGF-I-induced mRNA level of AR coactivators, suggesting that AR coactivators are post-transcriptionally regulated by IGF-I. Furthermore, the present results suggest that IGF-I stimulates the expression of AR coactivators by cooperative activation of the p38 MAPK and ERK1/2 pathways in C2C12 mouse skeletal muscle cells.