Abstract
MOLECULAR & CELLULAR BIOLOGY Animal Cells and Systems Vol. 16, No. 2, April 2012, 8794 Sung-Soo Park and Eungseok Kim* Chonnam University, Biological Sciences, Youngbong-dong, Buk-gu, Gwangju 500-757, Republic of Korea (Received 27 April 2011; received in revised form 23 June 2011; accepted 5 July 2011) Nur77 is a member of the nuclear receptor 4A (NR4A) subgroup, which has been implicated in energy metabolism. Although Nur77 is found in adipose tissue, where TR4 plays a key role in lipid homeostasis, the role of Nur77 in adipogenesis is still controversial. Although the Nur77 responsive element (AAAGGTCA) is partially overlapped with TR4-binding sites (AGGTCA n AGGTCA: n06), the regulatory role of Nur77 in TR4 function associated with adipocyte biology remains unclear. Here, we found that Nur77 inhibits adipogenesis and TR4 transcriptional activity. Treatment with a Nur77 agonist, 1,1-bis(3?-indolyl)-1-(p-anisyl)-methane, during 3T3-L1 adipocyte differentiation reduced adipogenesis. In reporter gene analysis, Nur77 specifically suppressed TR4 transcription activity but had little effect on PPARg transcription activity. Consistently, Nur77 also suppressed TR4-induced promoter activity of the TR4 target gene PEPCK, which is known to be important for glyceroneogenesis in adipose tissue. Furthermore, Nur77 suppressed TR4 binding to TR4 response elements without direct interaction with TR4, suggesting that Nur77 may inhibit TR4 transcription activity via binding competition for TR4-binding sites. Furthermore, DIM-C-pPhOCH substantially suppressed TR4-induced PEPCK expression in 3T3-L1 adipocytes. Together, our data demonstrate that Nur77 plays an inhibitory role in TR4-induced PEPCK expression in 3T3-L1 adipocytes. Keywords: Nur77; TR4; adipocytes; PEPCK Introduction in 3T3-L1 adipocytes results in decreased intracellular TG accumulation via downregulation of the FATP1 Adipose tissue stores excess nutrients in the form of gene (submitted). triacylglycerides (TGs) and mobilizes free fatty acids by Nur77, a member of the NR4A subfamily of NRs, lipolysis during periods of energy deprivation. Altera- controls target gene expression via binding to the tion of the metabolic functions of adipose tissue is NGFI-B response element (NBRE: AAAGGTCA) as frequently associated with insulin resistance and type 2 a monomer (Philips et al. 1997a; Wilson et al. 1991). diabetes (Rosen and MacDougald 2006). Nur77 is considered to play a role in adipogenesis, as TR4 (NR2C2), a member of the nuclear receptor the Nur77 gene is dramatically induced during adipo- (NR) superfamily, regulates the expression of target cyte differentiation. However, conflicting results have genes via binding to TR4 response elements (TR4REs) been reported concerning the role of Nur77 in adipo- consisting of various direct repeats of AGGTCA-like genesis. A recent study suggested that Nur77 plays an motifs (DR 0DR 6); it has the highest affinity for the inhibitory role in adipogenesis despite its sharp induc- DR1 element (Lee et al. 1997, 1999; Kim et al. 2003). tion in the early phase of differentiation (Chao et al. TR4 functions dominantly as a homodimer via direct 2008). In contrast, Fumoto et al. reported that Nur77 binding to DRs. In addition, TR4 is also able to bind to stimulates adipocyte differentiation (Fumoto et al. a single AGGTCA-like sequence as a monomer (Lee 2007). Considering these conflicting reports regarding et al. 2001). Like many other NRs, TR4 is known to the role of Nur77 in adipocyte differentiation, it is participate in other NR signaling pathways through highly possible that involvement of Nur77 in adipogen- binding competition for coactivators or DNA-binding esis could be affected by complicated metabolic milieus sites located in the promoter of target genes or through which control the activities of NRs important to heterodimer formation via protein-protein interactions adipocyte biology. Interestingly, Nur77 is also known (Lee et al. 1998; Shyr et al. 2002). Thus, it is highly to functionally and/or physically interact with other possible that TR4 fine-tunes energy homeostasis in transcription factors via binding competition for insulin-sensitive tissues such as liver, adipose, and coregulators or DNA-binding sites (Philips et al. skeletal muscle via cross-talk with other NRs. Recently, 1997b; Hong et al. 2004; Song et al. 2004). Since we and Kang et al. found that fat mass is significantly TR4 has broad binding affinities for various DRs and reduced in TR4-deficient mice (Kang et al. 2011; Kim monomeric AGGTCA-like sequences, we are interested et al. 2011). Consistent with the phenotype of TR4- in addressing the cross-talk between TR4 and Nur77 in deficient mice, we also found that knockdown of TR4 the regulation of energy metabolism in adipocytes. *Corresponding author. Email: ekim@chonnam.ac.kr ISSN 1976-8354 print/ISSN 2151-2485 online # 2012 Korean Society for Integrative Biology http://dx.doi.org/10.1080/19768354.2011.603748 http://www.tandfonline.com 88 S.-S. Park and E. Kim Here, we demonstrate that Nur77 specifically inhibits GTGACA-3?) and (antisense; 5?-GAGAAGATTGG- TR4 transcriptional activity through inhibition of TR4 TAGGGGAGGC-3?, mPEPCK (sense; 5?-TCAA binding to TR4REs, resulting in the suppression of CACCGACCTCCCTTAC-3?) and (antisense; 5?-CCC TR4-induced PEPCK expression in 3T3-L1 adipocytes. TAGCCTGTTCTCTGTGC-3?), 36B4 (sense; 5?-AGA TGCAGCAGATCCGCAT-3?) and (antisense; 5?-ATA TGAGGCAGCAGTTTCTCCAG-3?). Materials and methods Plasmids Glutathione-S-transferase (GST) pull-down assay and Plasmids pSG5-PPARg, pCMX-RXRa, pCMX-TR4, electrophoretic mobility shift assay (EMSA) TR4RE-Luc, PPRE-Luc, and pG5-Luc as well as fusion vectors Gal4-ER and VP-16 have been described GST pull-down assay and EMSA were performed as previously (Shyr et al. 2002; Song et al. 2006; Kim and described previously (Shyr et al. 2002). The following Kim 2011). Plasmid pcDNA3-HA-Nur77 was a gift oligonucleotides were used in EMSA: cDR1 (5?- from Dr. Keesook Lee (Chonnam Natl. Univ., Gwang- GATCTCTCTAGGTCAAAGGTCAATTTC-3?) and ju). The mouse PEPCK 5? promoter region consisting PEPCK-TR4RE (5?-CCTTCTCATGACCTTTGG of 472 to 79 bp was amplified by PCR from NIH- CCGTGGGAGTA-3?). 3T3 genomic DNA and then cloned into pGL3- luciferase (Promega) to generate pGL3-mPEPCK. Three copies of synthesized consensus DR1 (cDR1) Chromatin immunoprecipitation (ChIP) assay were cloned into pGL3-TK-Luc to create pGL3-TK- ChIP assay was performed in NIH-3T3 cells as cDR1. previously described (Park et al. 2008). Samples were immunoprecipitated with normal IgG (Santa Cruz) or anti-TR4 antibody (Santa Cruz). Primer sequences Cell culture, differentiation, and Oil Red O staining used for amplification of the region encompassing NIH-3T3, 3T3-L1, HEK293T, and CV-1 cells were TR4RE within the PEPCK 5? promoter were: maintained in DMEM containing 10% bovine calf TR4RE-sense 5?-AGGTAACACACCCCAGCTAAC- serum or FBS. 3T3-L1 cells stably transfected with 3?, TR4RE-antisense 5?-GGCTCTTGCCTTAATTGT pcDNA3 or pcDNA3-TR4 were maintained in CAG-3?. DMEM containing 800 mg/ml of Geneticin (Gibco). Adipocyte differentiation and Oil Red O staining were performed as described previously (Wang et al. 2010). Results Nur77 agonist inhibits adipogenesis of 3T3-L1 Transient transfection and luciferase assay preadipocytes Transfections were performed using SuperFect reagent We first determined whether DIM-C-pPhOCH ,a (Qiagen) according to the manufacturer’s instructions, Nur77 agonist, could affect adipogenesis of 3T3-L1 and luciferase activities were measured in a luciferase preadipocytes using Oil Red O staining. Two-day post- reporter assay system (Berthold). Relative luciferase confluent 3T3-L1 cells (designated day 0) were differ- activity (fold) was expressed based on induction entiated by addition of standard adipogenic stimuli. relative to the transfection of empty vector (set as 1- Twenty micromolar DIM-C-pPhOCH was also added fold) without agonist; the results are expressed as the on day 0 and continuously treated to 3T3-L1 cells mean9standard deviation (SD) of three separate throughout the course of differentiation. As shown in experiments. Figure 1a, treatment with DIM-C-pPhOCH signifi- cantly reduced TG accumulation in day 7 3T3-L1 adipocytes as compared with 3T3-L1 adipocytes trea- Reverse transcription PCR (RT-PCR) ted with vehicle. Next, we measured the levels of TR4 mRNA during adipogenesis by RT-PCR to determine mRNA levels of TR4, Nur77, PEPCK, and 36B4 were whether DIM-C-pPhOCH affects expression of TR4 determined by RT-PCR as described previously (Park during adipocyte differentiation. Consistent with a et al. 2008). Relative levels of PEPCK, TR4, and Nur77 previous report (Margolis et al. 2005), the TR4 mRNA were normalized to an internal control (36B4). mRNA level was lowest on day 2 and then progres- Primer sequences for the following genes were: TR4 sively increased until day 6 (Figure 1b). In addition, (sense; 5?-CAGCAGTTCATCCTAACCAGCCC-3?) DIM-C-pPhOCH did not significantly affect TR4 and (antisense; 5?-CTGCTCCGACAGCTGTAG GTC-3?), Nur77 (sense; 5?-CCACCTCTCCGAACC expression in 3T3-L1 adipocytes. Animal Cells and Systems 89 Figure 1. Effect of Nur77 agonist on adipocyte differentiation. (a) At 2 days post-confluence, 3T3-L1 cells were differentiated by standard protocol in the absence or presence of 20 mM DIM-C-pPhOCH and then stained with Oil Red O on day 7 to determine the effect of DIM-C-pPhOCH on adipogenesis. (b) 3T3-L1 cells were harvested on indicated days after the induction of differentiation and the mRNA levels of TR4, Nur77 and PEPCK were analyzed by RT-PCR analysis. The data shown are representative of three individual experiments (a and b). Relative mRNA levels of the PEPCK genes are expressed as mean9S.D. of three individual experiments (*PB 0.05). Nur77 selectively inhibits TR4 transcriptional activity Nur77 inhibits TR4 binding to TR4 responsive elements Since TR4 and PPARg are known to play essential To determine whether Nur77 inhibition of TR4 trans- roles in lipid metabolism and have binding affinities for activation occurs through physical association of DRs containing AGGTCA-like motifs, we investigated Nur77 with TR4, we first performed a GST pull- whether Nur77 could regulate the transcriptional down assay. As shown in Figure 3a, GST-TR4 fusion activities of TR4 and PPARg using reporter genes protein could interact with S-labeled estrogen recep- containing TR4 or PPARg response element (TR4RE- tor (ER), which has been reported to form a hetero- Luc or PPRE-Luc). Addition of DIM-C-pPhOCH dimer with TR4 (Shyr et al. 2002). However, we were resulted in inhibition of TR4 transactivation in unable to observe any interaction between S-labeled HEK293T cells, whereas DIM-C-pPhOCH did not Nur77 and GST-TR4 fusion protein. Next, we used a affect the transcriptional activity of PPARg (Figure mammalian two-hybrid assay to test whether Nur77 2a). To rule out any effect that sequence difference could affect the interaction between TR4 and ER. between these reporter genes may have, we tested the Consistent with a previous report (Shyr et al. 2002), effect of DIM-C-pPhOCH on TR4 and PPARg significant induction was observed when VP16-TR4 activities using a reporter gene fused with three copies was co-transfected with GAL4-ER into HEK293T cells of consensus DR1 (cDR1-Luc). As observed in the (Figure 3b). However, interaction between TR4 and above data, DIM-C-pPhOCH inhibited only TR4 ER was not affected by the addition of Nur77, transcriptional activity, suggesting that Nur77 may indicating that TR4 does not form a heterodimer have a negative effect on adipogenesis via specific with Nur77. It is also possible that Nur77 may inhibit modulation of TR4 activity. To evaluate whether TR4 transactivation via suppression of TR4 binding to DIM-C-pPhOCH inhibits TR4 activity in a cell- TR4REs. To investigate this possibility, we performed independent manner, we also performed reporter gene an EMSA using P-labeled cDR1 to determine the assays using cDR1-Luc in HEK293T, NIH-3T3, or effect of Nur77 on TR4 binding to cDR1. As expected, CV-1 cells. The addition of DIM-C-pPhOCH reduced in vitro translated TR4, but not Nur77 protein, formed TR4 transcriptional activity about 32 to 50% depend- a specific complex with P-labeled cDR1 (Figure 3c, ing on the cell line (Figure 2b). Co-transfection of left). However, the TR4/cDR1 complex was reduced by Nur77 with TR4 into these cells strongly suppressed the addition of Nur77 in a dose-dependent manner, TR4 activity. Further, addition of DIM-C-pPhOCH suggesting that despite very low affinity of Nur77 for together with Nur77 to TR4-transfected cells further cDR1, Nur77 may inhibit TR4 binding to cDR1. inhibited TR4 activity as compared with DIM-C- Furthermore, the negative effect of Nur77 on TR4 pPhOCH alone. binding to cDR1 was abolished by increasing amounts 3 90 S.-S. Park and E. Kim Figure 2. Nur77 specifically inhibits TR4 transcriptional activity. (a) Effect of Nur77 agonist on transcriptional activities of TR4 and PPARg. The indicated reporter genes (300 ng of each) were co-transfected with expression plasmids for PPARg, RXRa and TR4 (100 ng of each) into HEK293T cells. Transfected cells were incubated for 24 hr in the absence or presence of appropriate ligands (100 mM Rosiglitazone or/and 20 mM DIM-C-pPhOCH ) and then harvested to measure luciferase activity (**PB 0.01, ***PB 0.001). (b) The effect of Nur77 on TR4 transcriptional activity in different cells. Reporter gene (cDR1-Luc 100 ng) was co-transfected with the indicated combinations of TR4 or Nur77 expression plasmid (100 ng of each) into different cells as indicated. Transfected cells were incubated for 24 hr in the absence or presence of 20 mM DIM-C-pPhOCH and then luciferase activity was analyzed (*PB 0.05, **PB 0.01, ***PB 0.001). of TR4. When we used PEPCK-TR4RE as a probe, product was observed using DNA immunoprecipitated Nur77 similarly inhibited the formation of TR4/ with normal serum IgG (Figure 3e). In contrast, we PEPCK-TR4RE complex, and this suppression was observed specific binding of TR4 to the PEPCK also inhibited by increasing amounts of TR4 (Figure promoter region containing PEPCK-TR4RE, even though the PCR product band amplified from control 3c, right). The binding of Nur77 to cDR1 and PEPCK- cells was weaker than that of NIH-3T3 cells transfected TR4RE may not be observed due to different expres- with TR4. However, when Nur77 was co-transfected sion levels of in vitro translated TR4 and Nur77. To with TR4 into NIH-3T3 cells, we were not able to test this possibility, we examined the protein levels of observe any amplified PCR band. coupled in vitro transcription and translated Nur77 and TR4 with [ S]-Met by SDS-PAGE. The Nur77 protein level was similar to or higher than that of TR4 Nur77 suppresses TR4-induced PEPCK gene expression (Figure 3d). To further confirm Nur77 inhibition of in 3T3-L1 adipocytes TR4 binding to PEPCK-TR4RE, we performed a ChIP assay in NIH-3T3 cells transiently transfected Since Nur77 inhibited TR4 binding to PEPCK-TR4RE, with TR4 and/or Nur77 expression plasmids. PCR was we next determined if Nur77 could inhibit TR4 trans- performed to amplify the -529 to -245 bp region activation of the PEPCK promoter using a luciferase encompassing PEPCK-TR4RE from protein-DNA reporter linked to the PEPCK 5? promoter spanning complexes immunoprecipitated with normal serum 472 to 79 bp (pGL3-mPEPCK). As shown in IgG or anti-TR4 antibody. As expected, no PCR Figure 4a, TR4 induced PEPCK promoter activity Animal Cells and Systems 91 Figure 3. Nur77 inhibits TR4 biding to TR4 responsive elements. (a) GST pull-down assay was performed by incubation of S- labeled Nur77 or ER with GST or GST-TR4 bound glutathione-Sepharose beads. (b) The pG5-Luc (300 ng) was co-transfected with Gal4-ER, VP16-TR4 (100 ng of each) and Nur77 expression plasmid (100 ng) into HEK293T cells as indicated and luciferase activity was analyzed. (c) EMSAs were performed using P-labeled probes (cDR1 or PEPCK-TR4RE) with increasing amounts of in vitro translated TR4 or Nur77 as indicated. (d) After expression with [ S]-Met in a coupled-transcription and translation system (25 ml reaction), 3 ml in vitro translated TR4 and Nur77 were subjected to 10% SDS-PAGE for analysis of relative expression between samples. (e) Nur77 inhibition of TR4 binding to TR4RE within the mouse PEPCK 5? promoter. NIH- 3T3 cells were transiently transfected with TR4 and Nur77 expression plasmid (15 mg each) as indicated. Sixteen hr later, cells were harvested for ChIP assay. ChIP assay was performed using DNA-protein complex pulled-down by normal IgG, or anti-TR4 antibody as indicated. about 5.6-fold in HEK293T cells compared with control about 11-fold as compared with empty vector-trans- cells transfected with empty plasmid. Interestingly, when fected cells (Figure 4b). Interestingly, addition of Nur77 DIM-C-pPhOCH was treated to TR4-transfected did not reduce the basal level of PEPCK mRNA HEK293T cells, TR4 transcriptional activity was re- expression. However, when TR4 was co-transfected duced about 33%. DIM-C-pPhOCH -mediated sup- with Nur77, the induction effect of TR4 on PEPCK pression of TR4 activity could be attributed to the gene expression was reduced to 56% of that in TR4- activation of endogenous Nur77. Furthermore, Nur77 transfected cells. To further confirm the negative dramatically inhibited TR4 transcriptional activity effect of Nur77 on TR4-induced PEPCK expression when co-transfected with TR4 into HEK293T cells. in adipocytes, we investigated the effect of This effect of Nur77 on TR4 transactivation of the DIM-C-pPhOCH on TR4-induced PEPCK expression PEPCK promoter was further pronounced by increas- in 3T3-L1 cells stably overexpressing TR4. As shown in ing amounts of Nur77. We also obtained a similar result Figure 4d, RT-PCR analysis showed that TR4 over- when we performed the same reporter gene assay in expression resulted in a significant increase in PEPCK NIH-3T3 cells. Next, we evaluated the effect of Nur77 expression compared with control 3T3-L1 adipocytes on TR4 induction of the PEPCK gene by transient stably transfected with empty vector. However, treat- transfection of TR4 with or without Nur77 into NIH- ment with DIM-C-pPhOCH reduced TR4-induced 3T3 cells. As expected, RT-PCR analysis showed that PEPCK gene expression in 3T3-L1 adipocytes. To- TR4 induced mRNA expression of the PEPCK gene gether, these data indicate that Nur77 plays a role as a 92 S.-S. Park and E. Kim Figure 4. Nur77 suppresses PEPCK gene expression via inhibition of TR4 transcriptional activity. (a) HEK293T or NIH-3T3 cells were transfected with pGL3-mPEPCK-Luc (300 ng) and pCMX-TR4 (100 ng) with different amounts of Nur77 expression plasmid as indicated. Cells were treated with or without 20 mM DIM-C-pPhOCH for 24 hr and harvested for luciferase assays (***PB 0.001). (b) Expression plasmids for TR4 and Nur77 (6 mg of each) were transiently transfected into NIH-3T3 cells as indicated. Twenty-four hr later, cells were harvested for RT-PCR analysis. (c) DIM-C-pPhOCH inhibits TR4-induced PEPCK expression in 3T3-L1 adipocytes. At 2 days post-confluence, 3T3-L1 adipocytes stably overexpressing TR4 were differentiated by standard protocol in the absence or presence of 20 mM DIM-C-pPhOCH and harvested on day 4 for RT-PCR analysis. The data shown are representative of three individual experiments and relative mRNA levels of each gene are expressed as mean9S.D. of three individual experiments (b, c) (*PB 0.05). functional modulator of TR4 transcriptional activity in metabolic genes such as PEPCK. Here, we demon- 3T3-L1 adipocytes. strated that Nur77 negatively regulated TR4 transcrip- tional activity, resulting in decreased TR4-induced PEPCK expression in 3T3-L1 adipocytes. Nur77 is Discussion acutely induced during early adipogenesis of 3T3-L1 preadipocytes but subsequently declined to the basal TR4 is expressed in metabolic tissues such as adipose level within 24 hr (Fumoto et al. 2007; Chao et al. tissue, liver, and skeletal muscle and has been identified 2008). Although the level of Nur77 mRNA in the late as an important regulator of energy homeostasis (Kim phase of differentiation is much lower than its surge et al. 2003, Kim et al. 2011; Liu et al. 2007; Kang et al. after adipogenic activation, Nur77 expression is 2011). TR4 regulates gluconeogenesis through hepatic progressively increased during adipocyte differentiation induction of the PEPCK gene (Liu et al. 2007). In (Chao et al. 2008). Conflicting reports on the role of addition, TR4-deficient mice show reduced TG accu- mulation in adipose tissue (Kang et al. 2011; Kim et al. Nur77 in adipogenesis have been reported. Fumoto 2011). et al. reported that Nur77 is induced in the very early phase of adipogenesis by treatment with a differentia- Early studies have reported that several NRs regulate the expression of PEPCK in the liver (Chak- tion cocktail and promotes adipogenesis by triggering ravarty et al. 2005). Thus, differential activation of clonal expansion (Fumoto et al. 2007). In contrast, a NRs under particular metabolic cues might be critical recent report showed that NR4A NRs, including for determining the spatial and temporal control of Nur77, inhibit adipogenesis in different cell lines Animal Cells and Systems 93 (Chao et al. 2008). It has been reported that Nur77 ing in decreased expression of PEPCK in 3T3-L1 regulates target gene expression via binding to adipocytes. Our findings imply that TR4 is a key AAAGGTCA-like motifs as a monomer (Wilson et modulator of the NR network important for lipid al. 1991; Philips et al. 1997a). TR4 usually regulates homeostasis, and thus our study will help others to target gene expression via binding to DRs as a TR4 understand the transcriptional network involved in homodimer or heterodimer with TR2 (Lee et al. 1998). obesity-related diseases. Interestingly, a previous report showed that TR4 is also able to bind to monomeric AAAGGTCA-like se- Acknowledgements quences (Lee et al. 2001), strongly suggesting that these two NRs might functionally cross-talk with each This work was supported by a National Research Foundation of Korea Grant funded by the Korean Government (KRF- other to fine-tune adipocyte biology. As expected, 2006-312-C00392). We thank Dr. Keesook Lee for kindly Nur77 inhibited TR4 transcriptional activity at least providing plasmid. in part by suppressing TR4 binding to TR4REs. However, we were not able to observe Nur77 binding to this TR4RE. Since TR4 could form a heterodimer References with ER, leading to a loss of TR4 binding affinity for Chakravarty K, Cassuto H, Reshef L, Hanson RW. 2005. TR4RE, it is possible that Nur77 inhibition of TR4 Factors that control the tissue-specific transcription of activity could occur via heterodimerization with TR4. the gene for phosphoenolpyruvate carboxykinase-C. Crit Rev Biochem Mol Biol. 40(3):129154. However, TR4 showed no interaction with Nur77 in Chao LC, Bensinger SJ, Villanueva CJ, Wroblewski K, this study. Interestingly, both Nur77 and TR4 have Tontonoz P. 2008. Inhibition of adipocyte differentiation been shown to interact with several common coregu- by Nur77, Nurr1, and Nor1. Mol Endocrinol. lators such as SRC-1 (Wansa et al. 2002; Zhou et al. 22(12):25962608. 2011). Various NRs frequently participate in other NR Forest C, Tordjman J, Glorian M, Duplus E, Chauvet G, signaling pathways through competitive binding for Quette J, Beale EG, Antoine B. 2003. Fatty acid recycling in adipocytes: a role for glyceroneogenesis and phos- coactivators and several coactivators are known to phoenolpyruvate carboxykinase. Biochem Soc Trans. facilitate NR DNA binding activity (Yan et al. 1998; 31(Pt 6):11251129. Nakajima et al. 2004). Thus, it is also plausible that Fumoto T, Yamaguchi T, Hirose F, Osumi T. 2007. Orphan Nur77 may compete with TR4 for limited amounts of nuclear receptor Nur77 accelerates the initial phase of the endogenous coactivator which is important for the adipocyte differentiation in 3T3-L1 cells by promoting mitotic clonal expansion. J Biochem. 141(2):181192. stable binding of TR4 to TR4REs located in its target Hong CY, Park JH, Ahn RS, Im SY, Choi HS, Soh J, Mellon gene promoters. When Nur77 is highly expressed or SH, Lee K. 2004. 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Journal
Animal Cells and Systems
– Taylor & Francis
Published: Apr 1, 2012
Keywords: Nur77; TR4; adipocytes; PEPCK
