PPARγ is a member of the PPAR subfamily of nuclear receptors. In this work, the structure of the human PPARγ cDNA and gene was determined, and its promoters and tissue-specific expression were functionally characterized. Similar to the mouse, two PPAR isoforms, PPARγ1 and PPARγ2, were detected in man. The relative expression of human PPARγ was studied by a newly developed and sensitive reverse transcriptase-competitive polymerase chain reaction method, which allowed us to distinguish between PPARγ1 and γ2 mRNA. In all tissues analyzed, PPARγ2 was much less abundant than PPARγ1. Adipose tissue and large intestine have the highest levels of PPARγ mRNA; kidney, liver, and small intestine have intermediate levels; whereas PPARγ is barely detectable in muscle. This high level expression of PPARγ in colon warrants further study in view of the well established role of fatty acid and arachidonic acid derivatives in colonic disease. Similarly as mouse PPARγs, the human PPARγs are activated by thiazolidinediones and prostaglandin J and bind with high affinity to a PPRE. The human PPARγ gene has nine exons and extends over more than 100 kilobases of genomic DNA. Alternate transcription start sites and alternate splicing generate the PPARγ1 and PPARγ2 mRNAs, which differ at their 5′-ends. PPARγ1 is encoded by eight exons, and PPARγ2 is encoded by seven exons. The 5′-untranslated sequence of PPARγ1 is comprised of exons A1 and A2, whereas that of PPARγ2 plus the additional PPARγ2-specific N-terminal amino acids are encoded by exon B, located between exons A2 and A1. The remaining six exons, termed 1 to 6, are common to the PPARγ1 and γ2. Knowledge of the gene structure will allow screening for PPARγ mutations in humans with metabolic disorders, whereas knowledge of its expression pattern and factors regulating its expression could be of major importance in understanding its biology. PPARγ is a member of the PPAR subfamily of nuclear receptors. In this work, the structure of the human PPARγ cDNA and gene was determined, and its promoters and tissue-specific expression were functionally characterized. Similar to the mouse, two PPAR isoforms, PPARγ1 and PPARγ2, were detected in man. The relative expression of human PPARγ was studied by a newly developed and sensitive reverse transcriptase-competitive polymerase chain reaction method, which allowed us to distinguish between PPARγ1 and γ2 mRNA. In all tissues analyzed, PPARγ2 was much less abundant than PPARγ1. Adipose tissue and large intestine have the highest levels of PPARγ mRNA; kidney, liver, and small intestine have intermediate levels; whereas PPARγ is barely detectable in muscle. This high level expression of PPARγ in colon warrants further study in view of the well established role of fatty acid and arachidonic acid derivatives in colonic disease. Similarly as mouse PPARγs, the human PPARγs are activated by thiazolidinediones and prostaglandin J and bind with high affinity to a PPRE. The human PPARγ gene has nine exons and extends over more than 100 kilobases of genomic DNA. Alternate transcription start sites and alternate splicing generate the PPARγ1 and PPARγ2 mRNAs, which differ at their 5′-ends. PPARγ1 is encoded by eight exons, and PPARγ2 is encoded by seven exons. The 5′-untranslated sequence of PPARγ1 is comprised of exons A1 and A2, whereas that of PPARγ2 plus the additional PPARγ2-specific N-terminal amino acids are encoded by exon B, located between exons A2 and A1. The remaining six exons, termed 1 to 6, are common to the PPARγ1 and γ2. Knowledge of the gene structure will allow screening for PPARγ mutations in humans with metabolic disorders, whereas knowledge of its expression pattern and factors regulating its expression could be of major importance in understanding its biology. White adipose tissue is composed of adipocytes, which play a central role in lipid homeostasis and the maintenance of energy balance in vertebrates. These cells store energy in the form of triglycerides during periods of nutritional affluence and release it in the form of free fatty acids at times of nutritional deprivation. Excess of white adipose tissue leads to obesity (1Auwerx J. Martin G. Guerre-Millo G. Staels B. J. Mol. Med. 1996; 74: 347-352Crossref PubMed Scopus (64) Google Scholar, 2Flier J.S. Cell. 1995; 80: 15-18Abstract Full Text PDF PubMed Scopus (267) Google Scholar, 3Spiegelman B.M. Flier J.S. Cell. 1996; 87: 377-389Abstract Full Text Full Text PDF PubMed Scopus (1156) Google Scholar), whereas its absence is associated with lipodystrophic syndromes (4Moller D.E. Flier J.S. N. Engl. J. Med. 1991; 325: 938-948Crossref PubMed Scopus (767) Google Scholar). In contrast to the development of brown adipose tissue, which mainly takes place before birth, the development of white adipose tissue is the result of a continuous differentiation/development process throughout life (2Flier J.S. Cell. 1995; 80: 15-18Abstract Full Text PDF PubMed Scopus (267) Google Scholar, 5Auwerx, J., Schoonjans, K., Fruchart, J. C., and Staels, B. (1996)Atherosclerosis , 124, (suppl.) S29–S37.Google Scholar). During development, cells that are pluripotent become increasingly restricted to specific differentiation pathways. Adipocyte differentiation results from coordinate changes in the expression of several proteins, which are mostly involved in lipid storage and metabolism, that give rise to the characteristic adipocyte phenotype. The changes in expression of these specialized proteins are mainly the result of alterations in the transcription rates of their genes. Several transcription factors including the nuclear receptor PPARγ (6Tontonoz P. Hu E. Graves R.A. 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Bucher N.L.R. Farmer S.R. Genes & Dev. 1995; 9: 2350-2363Crossref PubMed Scopus (478) Google Scholar), which then triggers the adipogenic program. Terminal differentiation then requires the concerted action of both PPARγ, C/EBPα, and ADD-1/SREBP1 (7Tontonoz P. Hu E. Spiegelman B.M. Cell. 1994; 79: 1147-1156Abstract Full Text PDF PubMed Scopus (3114) Google Scholar,15Kim J.B. Spiegelman B.M. Genes & Dev. 1996; 10: 1096-1107Crossref PubMed Scopus (842) Google Scholar). Several arguments support the important role of PPARγ in adipocyte differentiation. First, overexpression of PPARγ by itself can induce adipocyte conversion of fibroblasts (6Tontonoz P. Hu E. Graves R.A. Budavari A.I. Spiegelman B.M. Genes & Dev. 1994; 8: 1224-1234Crossref PubMed Scopus (1996) Google Scholar). In addition, PPARγ together with C/EBPα can induce transdifferentiation of myoblasts into adipocytes (19Hu E. Tontonoz P. Spiegelman B.M. Proc. Natl. Acad. Sci. U. S. 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Chem. 1995; 270: 19269-19276Abstract Full Text Full Text PDF PubMed Scopus (355) Google Scholar), and lipoprotein lipase (LPL) (23Schoonjans K. Peinado-Onsurbe J. Heyman R. Briggs M. Cayet D. Deeb S. Staels B. Auwerx J. EMBO J. 1996; 15: 5336-5348Crossref PubMed Scopus (1017) Google Scholar), is consistent with the crucial role attributed to PPARγ in adipocyte differentiation. Finally, PPAR activators, such as fibrates (24Brandes R. Hertz R. Arad R. Naishtat S. Weil S. Bar-Tana J. Life Sci. 1987; 40: 935-941Crossref PubMed Scopus (24) Google Scholar, 25Gharbi-Chibi J. Teboul M. Bismuth J. Bonne J. Torresani J. Biochim. Biophys. Acta. 1993; 1177: 8-14Crossref PubMed Scopus (23) Google Scholar) and fatty acids (7Tontonoz P. Hu E. Spiegelman B.M. Cell. 1994; 79: 1147-1156Abstract Full Text PDF PubMed Scopus (3114) Google Scholar, 26Amri E.-Z. Bertrand B. Ailhaud G. Grimaldi P. J. Lipid Res. 1991; 32: 1449-1456Abstract Full Text PDF PubMed Google Scholar, 27Chawla A. Lazar M.A. Proc. 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Both PPARγ1 and 2 are produced in human tissues but PPARγ2 appears to be the minor isoform in man. In addition to adipose tissue, which contains high levels of PPARγ, we demonstrate high level expression of human PPARγ in the colon. The structure of the gene encoding the mouse and human PPARγs is highly conserved. Furthermore our results demonstrate that 3 and 1 kb of DNA upstream of the transcription start sites of PPARγ1 and γ2, respectively, are sufficient to control basal and tissue-specific PPARγ gene expression. The oligonucleotides used for various experiments in this manuscript are listed in Table I.Table IOligonucleotides used in this study listed from 5′ to 3′NameSequenceLF-2TCTCCGGTGTCCTCGAGGCCGACCCAALF-14AGTGAAGGAATCGCTTTCTGGGTCAATLF-18AGCTGATCCCAAAGTTGGTGGGCCAGALF-20CATTCCATTCACAAGAACAGATCCAGTGGTLF-21GGCTCTTCATGAGGCTTATTGTAGAGCTGALF-22GCAATTGAATGTCGTGTCTGTGGAGATAALF-23GTGGATCCGACAGTTAAGATCACATCTGTLF-24GTAGAAATAAATGTCAGTACTGTCGGTTTCLF-25TCGATATCACTGGAGATCTCCGCCAACAGLF-26ACATAAAGTCCTTCCCGCTGACCAAAGCAALF-27CTCTGCTCCTGCAGGGGGGTGATGTGTTTLF-28GAAGTTCAATGCACTGGAATTAGATGACALF-29GAGCTCCAGGGGTTGTAGCAGGTTGTCTTLF-33GACGGGCTGAGGAGAAGTCACACTCTGALF-35AGCATGGAATAGGGGTTTGCTGTAATTCLF-36TAGTACAAGTCCTTGTAGATCTCCLF-44GTCGGCCTCGAGGACACCGGAGAGLF-58CACTCATGTGACAAGACCTGCTCCLF-59GCCGACACTAAACCACCAATATACLF-60CGTTAAAGGCTGACTCTCGTTTGAAII J PPREGATCCTTCAACCTTTACCCTGGTAGAACO PPREGATCCCGAACGTGACCTTTGTCCTGGTCCCLPL PPREGATCCGTCTGCCCTTTCCCCCTCTTCAγASGCATTATGAGCATCCCCACγSTCTCTCCGTAATGGAAGACCγ2SGCGATTCCTTCACTGATACCDSTTCTAGAATTCAGCGGCCGC(T)30(G/A/C)(G/A/C/T) Open table in a new tab A human adipose tissue λgt11 library was screened with a random primed 32P-labeled 200 bp fragment, covering the DNA-binding domain of the mouse PPARγ cDNA. After hybridization, filters were washed in 2 × SSC, 0.1% SDS for 10 min at 20 °C and twice for 30 min in 1 × SSC, 0.1% SDS at 50 °C and subsequently exposed to x-ray film (X-OMAT-AR, Kodak). Of several positive clones, one clone 407 was characterized in detail. The insert of this clone, starting ±90 bp upstream of the ATG start codon and extending downstream into the 3′-untranslated region (UTR) sequence, was subcloned in the EcoRI site of pBluescript SK− to generate clone 407.2. Sequence analysis of 407.2 confirmed it as being the human homologue of the mouse PPARγ2 cDNA. While this work was in progress, other groups also reported the isolation of human PPARγ2 cDNA clones (34Elbrecht A. Chen Y. Cullinan C.A. Hayes N. Leibowitz M.D. Moller D.E. Berger J. Biochem. Biophys. Res. Commun. 1996; 224: 431-437Crossref PubMed Scopus (353) Google Scholar, 35Lambe K.G. Tugwood J.D. Eur. J. Biochem. 1996; 239: 1-7Crossref PubMed Scopus (198) Google Scholar). To isolate genomic P1-derived artificial chromosome (PAC) clones containing the entire human PPARγ gene, the primer pair LF-3 and LF-14 was used to amplify an 86-bp probe with human genomic DNA as template. This fragment was then used to screen a PAC human genomic library from human foreskin fibroblasts. Three positive clones, P-8854, P-8855, and P-8856, were isolated. Restriction digestion and Southern blotting were performed according to classical protocols as described by Sambrook et al. (36Sambrook J. Fritsch E.F. Maniatis T. Molecular Cloning: A Laboratory Manual. Cold Spring Harbor Laboratory Press, Cold Spring Harbor, NY1989Google Scholar). Sequencing reactions were performed, according to the manufacturer instructions, using the T7 sequencing kit (Pharmacia Biotech Inc.). The oligonucleotide LF-35 was32P-labeled with T4-polynucleotide kinase (Amersham Life Science, Inc) to a specific activity of 107 dpm/50 ng and purified by gel electrophoresis. For primer extension, 105dpm of oligonucleotide was added in a final volume of 100 μl to 50 μg of adipose tissue total RNA isolated from different patients. Primer extension analysis was performed following standard protocols utilizing a mixture of 1.25 units of avian mycloblastosis virus reverse transcriptase (Life Technologies, Inc.) and 100 units of Moloney murine leukemia virus reverse transcriptase (Life Technologies, Inc.). A sequencing reaction and molecular mass standards were used to map the 5′-end of the extension products. The Marathon cDNA amplification kit (CLONTECH) was used to obtain a library of adaptor-ligated double-stranded cDNA from human adipose tissue. 1 μg of poly(A)+ RNA was used as a template for the first strand synthesis, with the 52-mer CDS primer and 100 units of the MMLV reverse transcriptase in a total volume of 10 μl. Synthesis was carried out at 42 °C for 1 h. Next, the second strand was synthetized at 16 °C for 90 min in a total volume of 80 μl containing the enzyme mixture (RNase H, Escherichia coli DNA polymerase I, and E. coli DNA ligase), the second strand buffer, the dNTP mix, and the first strand reaction. cDNA ends were then made blunt by adding to the reaction 10 units of T4 DNA polymerase and incubating at 16 °C for 45 min. The double-stranded cDNA was phenol/chloroform extracted, ethanol precipitated, and resuspended in 10 μl of water. Half of this volume was used to ligate the adaptor to the cDNA ends (adaptor sequence CTAATACGACTCACTATAGGGCTCGAGCGGCCGCCCGGGCAGGT) in a total volume of 10 μl using 1 unit of T4 DNA ligase. The ligation reaction was incubated 16 h at 16 °C. The resulting cDNA library was diluted to a final concentration of 0.1 mg/ml. The 5′-end of PPARγ1 was PCR-amplified using 5 μl of the library as a template with the oligonucleotides AP-1 (binding to the adaptor) and LF-45 (binding antisense to the 5′-end of the PPARγ1). After an initial denaturing step at 95 °C for 3 min, 25 cycles were done at the following conditions: 10 s at 95 °C, 20 s at 60 °C, and 30 s at 72 °C. The resulting PCR product was reamplified for 30 additional cycles at the same conditions using the nested oligonucleotides AP2 (nested to AP1) and LF-2 (nested to LF-45). The PCR product was analyzed on a 2% agarose gel, treated withPfu polymerase (Stratagene) and cloned into theEcoRV site of pBluescript SK+. A total of 20 white colonies were grown and sequenced from both ends using the oligonucleotides T3 and T7 (Dye Terminator Cycle sequencing kit, Applied Biosystems). For the determination of the 5′-end of PPARγ2, the same procedure was followed except that the oligonucleotide LF-14 (specific for the PPARγ2 5′-UTR) was used in the first round PCR, and the oligonucleotide LF-35 (nested to LF-14) was used in the second round PCR with the same cycling conditions. Omental adipose tissue, small and large intestine, kidney, muscle, and liver biopsies were obtained from non-obese adult subjects undergoing elective surgery or endoscopy. All subjects had fasted overnight before surgery (between 8.00 p.m. and 10 a.m.) and received intravenous saline infusion. They had given informed consent, and the project was approved by the ethics committee of the University of Lille. All tissue was immediately frozen in liquid nitrogen until RNA preparation. Standard cell culture conditions were used to maintain 3T3-L1 (obtained from ATCC), CV-1 (a kind gift from Dr. R. Evans, Salk Institute, La Jolla, CA), and Hep G2 cells (ATCC). BRL-49,653, supplied by Ligand Pharmaceuticals, San Diego, CA (in DMSO) and fatty acids (in ethanol) were added to the medium at the concentrations and times indicated. Control cells received vehicle only. Fatty acids were complexed to serum albumin contained in delipidated and charcoal-treated fetal calf serum by preincubation for 45 min at 37 °C. RNA preparation of total cellular RNA was performed as described previously (37Saladin R. De Vos P. Guerre-Millo M. Leturque A. Girard J. Staels B. Auwerx J. Nature. 1995; 377: 527-529Crossref PubMed Scopus (1092) Google Scholar). The absolute mRNA concentration of the differentially spliced PPARγ variants was measured by reverse transcription reaction followed by competitive polymerase chain reaction (RT-competitive PCR) in the presence of known amounts of competitor DNA yielding amplicons of different size allowing the separation and the quantification of the PCR products. The competitor was constructed by deletion of a 74-bp fragment (nucleotides +433 to +507 by HindIII digestion) of PPARγ1 cloned into pBluescript KS+, yielding pBSCompPPARγ. Working solution of the competitor was prepared by in vitro transcription followed by serial dilution in 10 mm Tris-HCl (pH 8.3), 1 mm EDTA buffer. For RT-competitive PCR, the antisense primer hybridized to the 3′-end of exon 3 (γAS:5′-GCATTATGAGCATCCCCAC-3′, nt +600 to +620) and the sense primer to exon 1 (γS:5′-TCTCTCCGTAATGGAAGACC-3′, nt +146 to +165) or to the B exon (γ2S:5′-GCGATTCCTTCACTGATAC-3′, nt +41 to +59). Therefore, the same competitor served to measure either total PPARγ mRNAs (γ1 + γ2; with primers γAS and γS) or, specifically, PPARγ2 mRNA (with primers γAS and γ2S). The γAS/γS primer pair gave PCR products of 474 and 400 bp for the PPARγ mRNAs and competitor, respectively. The primer pair γAS/γ2S gave 580 bp for PPARγ2 mRNA and 506 bp for the competitor. For analysis of the PCR products, the sense primers γS and γ2S were 5′-end labeled with the fluorescent dye Cy-5 (Eurogentec, Belgium). First-strand cDNA synthesis was performed from total RNA (0.1 μg) in the presence of the antisense primer γAS (15 pmol) and of thermostable reverse transcriptase (2.5 units; Tth DNA polymerase, Promega) as described (38Vidal H. Auboeuf D. De Vos P. Staels B. Riou J.P. Auwerx J. Laville M. J. Clin. Invest. 1996; 98: 251-255Crossref PubMed Scopus (184) Google Scholar). After the reaction, half of the RT volume was added to the PCR mix (90 μl) containing the primer pair γAS/γS for the assay of PPARγ total mRNA, whereas the other half was added to a PCR mix (10 mm Tris-HCl, pH 8.3, 100 mm KCl, 0.75 m EGTA, 5% glycerol, 0.2 mm dNTP, 5 units of Taq polymerase) containing the primer pair γAS/γ2S for the assay of PPARγ2 mRNA. Four aliquots (20 μl) of the mixture were then transferred to microtubes containing a different, but known, amount of competitor. After 120 s at 95 °C, the samples were subjected to 40 PCR cycles (40 s at 95 °C, 50 s at 55 °C, and 50 s at 72 °C). The fluorescent-labeled PCR products were analyzed by 4% denaturing polyacrylamide gel electrophoresis using an automated laser fluorescence DNA sequencer (ALFexpress, Pharmacia, Uppsala, Sweden), and integration of the area under the curve using the Fragment manager software (Pharmacia) was performed as described (38Vidal H. Auboeuf D. De Vos P. Staels B. Riou J.P. Auwerx J. Laville M. J. Clin. Invest. 1996; 98: 251-255Crossref PubMed Scopus (184) Google Scholar). To validate this technique, human PPARγ2 mRNA was synthesized byin vitro transcription from the expression vector pSG5hPPARγ (Riboprobe system, Promega) and quantified by competitive PCR over a wide range of concentrations (0.25–25 attomole (amol) added in the RT reaction). Standard curves obtained when assaying PPARγ total mRNA or PPARγ2 mRNA are shown in Fig. 2 C. The linearity (r = 0.99) and the slopes of the standard curves (0.98 and 1.11) indicated that the RT-competitive PCR is quantitative and that all the mRNA molecules are copied into cDNA during the RT step. The lower limit of the assay was about 0.05 amol of mRNA in the RT reaction, and the interassay variation of the RT-competitive PCR was 7% with six separated determinations of the same amount of PPARγ mRNA. Cells and tissues were homogenized in a lysis buffer of PBS containing 1% Triton X-100 (Sigma). Tissues were homogenized in extraction buffer containing PBS and 1% Nonidet P-40 (Sigma), 0.5% sodium deoxycholate (Sigma), 0.1% SDS (Sigma). Fresh mixture protease inhibitor (ICN) was added (100 mg/ml AEBSF, 5 mg/ml EDTA, 1 mg/ml leupeptin, 1 mg/ml pepstatin). Protein extracts were obtained by centrifugation of the lysate at 4 °C, and concentration was measured with the Bio-Rad DC Protein colorimetric assay system. Protein (100 μg) was separated by SDS-PAGE, transferred to nitrocellulose membrane (Amersham Life Science, Inc.), and blocked overnight in blocking buffer (20 mm Tris, 100 mm NaCl, 1% Tween-20, 10% skim milk). Filters were first incubated for 4 h at room temperature with rabbit IgG anti-mPPARγ (10 mg/ml), raised against an N-terminal PPARγ peptide (amino acids 20–104), and next developed for 1 h at room temperature with a goat anti-rabbit IgG (whole molecule) peroxidase conjugate (Sigma) diluted at 1/500. The complex was visualized with 4-chloro-1-naphtol as reagent. To test the activity of the human PPARγ promoters several reporter constructs were made. A 1-kb fragment of PAC clone 8856 was isolated by PCR using the oligonucleotides LF-35 (binding antisense in the PPARγ2 5′-UTR) and the oligonucleotide LF-58 (binding sense at position -1000 of the PPARγ2), was sequenced, and was inserted intoEcoRV site of pBluescript (Stratagene, La Jolla, CA). After digestion of plasmid pBSγ2p1000 with SmaI andKpnI, the insert was cloned into the reporter vector pGL3 (Promega), creating the expression vector pGL3γ2p1000. To isolate the PPARγ1 promoter, an 8-kb EcoRI fragment, which hybridized with the oligonucleotide LF-2 (corresponding to the 5′-UTR of γ1), was cloned into pBluescript. Partial mapping and sequencing of this clone revealed the presence of a 3-kb fragment upstream of the transcription initiation site. To test for promoter activity, aSacI/XhoI digestion of this clone containing the 3-kb promoter was inserted in the same sites of pGL3, resulting in the final vector pGL3γ1p3000. The pSG5-haPPARγ (39Aperlo C. Pognonec P. Saladin R. Auwerx J. Boulukos K. Gene ( Amst. ). 1995; 162: 297-302Crossref PubMed Scopus (74) Google Scholar) and pMSV-C/EBPα (10Christy R.J. Yang V.W. Ntambi J.M. Geiman D.E. Landschulz W.H. Friedman A.D. Nakabeppu Y. Kelly T.J. Lane M.D. Genes & Dev. 1989; 3: 1323-1335Crossref PubMed Scopus (466) Google Scholar) expression vectors were described elsewhere. Transfections were carried out in 60-mm plates using standard calcium phosphate precipitation techniques (for 3T3-L1, CV-1, and COS cells) (22Schoonjans K. Watanabe M. Suzuki H. Mahfoudi A. Krey G. Wahli W. Grimaldi P. Staels B. Yamamoto T. Auwerx J. J. Biol. Chem. 1995; 270: 19269-19276Abstract Full Text Full Text PDF PubMed Scopus (355) Google Scholar). Luciferase and β-galactosidase assays were carried out exactly as described previously (22Schoonjans K. Watanabe M. Suzuki H. Mahfoudi A. Krey G. Wahli W. Grimaldi P. Staels B. Yamamoto T. Auwerx J. J. Biol. Chem. 1995; 270: 19269-19276Abstract Full Text Full Text PDF PubMed Scopus (355) Google Scholar). haPPARγ (39Aperlo C. Pognonec P. Saladin R. Auwerx J. Boulukos K. Gene ( Amst. ). 1995; 162: 297-302Crossref PubMed Scopus (74) Google Scholar), hPPARγ2, and mRXRα (40Leid M. Kastner P. Lyons R. Nakshatri H. Saunders M. Zacharewski T. Chen J.Y. Staub A. Garnier J.M. Mader S. Chambon P. Cell. 1992; 68: 377-395Abstract Full Text PDF PubMed Scopus (1019) Google Scholar) proteins were synthesized in vitro in rabbit reticulocyte lysate (Promega). Molecular weights and quality of the in vitrotranslated proteins were verified by SDS-PAGE. PPAR (2 μl) and/or RXR (2 μl) were incubated for 15 min on ice in a total volume of 20 μl with 1-ng probe, 2.5 μg of poly(dI-dC) and 1 μg of herring sperm DNA in binding buffer (10 mm Tris-HCl pH 7.9, 40 mm KCl, 10% glycerol, 0.05% Nonidet P-40, and 1 mm dithiothreitol). For competition experiments, increasing amounts (from 10- to 200-fold molar excess) of cold oligonucleotide (AII-J-PPRE, 5′-GATCCTTCAACCTTTACCCTGGTAGA-3′ (41Vu-Dac N. Schoonjans K. Kosykh V. Dallongeville J. Fruchart J.-C. Staels B. Auwerx J. J. Clin. 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