mPPAR gamma 2: tissue-specific regulator of an adipocyte enhancer.
Previously, we have isolated and characterized an enhancer from the 5'-flanking region of the adipocyte P2 (aP2) gene that directs high-level adipocyte-specific gene expression in both cultured cells and transgenic mice. The key regulator of this enhancer is a cell type-restricted nuclear factor termed ARF6. Target sequences for ARF6 in the aP2 enhancer exhibit homology to a direct repeat of hormone response elements (HREs) spaced by one nucleotide; this motif (DR-1) has been demonstrated previously to be the preferred binding site for heterodimers of the retinoid X receptor (RXR) and the peroxisome proliferator-activated receptor (PPAR). We have cloned a novel member of the peroxisome proliferator-activated receptor family designated mPPAR gamma 2, and we demonstrate that a heterodimeric complex of mPPAR gamma 2 and RXR alpha constitute a functional ARF6 complex. Expression of mPPAR gamma 2 is induced very early during the differentiation of several cultured adipocyte cell lines and is strikingly adipose-specific in vivo. mPPAR gamma 2 and RXR alpha form heterodimers on ARF6-binding sites in vitro, and antiserum to RXR alpha specifically inhibits ARF6 activity in adipocyte nuclear extracts. Moreover, forced expression of mPPAR gamma 2 and RXR alpha activates the adipocyte-specific aP2 enhancer in cultured fibroblasts, and this activation is potentiated by peroxisome proliferators, fatty acids, and 9-cis retinoic acid. These results identify mPPAR gamma 2 as the first adipocyte-specific transcription factor and suggest mechanisms whereby fatty acids, peroxisome proliferators, 9-cis retinoic acid, and other lipids may regulate adipocyte gene expression and differentiation.
Tontonoz
P
P
Dana-Farber Cancer Institute, Boston, Massachusetts.
Hu
E
E
Graves
R A
RA
Budavari
A I
AI
Spiegelman
B M
BM
D016475:3T3 Cells; D020727:ADP-Ribosylation Factors; D017667:Adipocytes / Q000737:chemistry / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D002352:Carrier Proteins / Q000235:genetics; D002460:Cell Line; D003001:Cloning, Molecular; D004247:DNA / Q000378:metabolism; D004742:Enhancer Elements, Genetic / Q000502:physiology*; D000071438:Fatty Acid-Binding Protein 7; D050556:Fatty Acid-Binding Proteins; D019204:GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D005786:Gene Expression Regulation / Q000502:physiology*; D051379:Mice; D008969:Molecular Sequence Data; D009363:Neoplasm Proteins; D009419:Nerve Tissue Proteins; D009687:Nuclear Proteins / Q000378:metabolism; D009928:Organ Specificity; D012333:RNA, Messenger / Q000032:analysis; D018160:Receptors, Cytoplasmic and Nuclear / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D018168:Receptors, Retinoic Acid; D047488:Retinoid X Receptors; D017422:Sequence Analysis, DNA; D012689:Sequence Homology, Nucleic Acid; D014157:Transcription Factors / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism
D002352:Carrier Proteins; C082667:Fabp5 protein, mouse; C086936:Fabp7 protein, mouse; D000071438:Fatty Acid-Binding Protein 7; D050556:Fatty Acid-Binding Proteins; D009363:Neoplasm Proteins; D009419:Nerve Tissue Proteins; D009687:Nuclear Proteins; D012333:RNA, Messenger; D018160:Receptors, Cytoplasmic and Nuclear; D018168:Receptors, Retinoic Acid; D047488:Retinoid X Receptors; D014157:Transcription Factors; D004247:DNA; D019204:GTP-Binding Proteins; D020727:ADP-Ribosylation Factors