Functional antagonism between inhibitor of DNA binding (Id) and adipocyte determination and differentiation factor 1/sterol regulatory element-binding protein-1c (ADD1/SREBP-1c) trans-factors for the regulation of fatty acid synthase promoter in adipocytes.
We show that Id (inhibitor of DNA binding) 2 and Id3, dominant negative members of the helix-loop-helix (HLH) family, interact with the adipocyte determination and differentiation factor 1 (ADD1)/sterol regulatory element-binding protein (SREBP) 1c, a transcription factor of the basic HLH-leucine zipper family that controls the expression of several key genes of adipose metabolism. Gel mobility-shift assays performed with in vitro-translated ADD1, Id2 or Id3 proteins and a fatty acid synthase (FAS) promoter oligonucleotide showed evidence for a marked inhibition of the formation of DNA-ADD1 complexes by Id2 or Id3 proteins. Co-immunoprecipitation studies using in vitro-translated proteins demonstrated further the physical interaction of Id and ADD1/SREBP-1c proteins in the absence of DNA. Using the FAS gene as a model of an ADD1-regulated promoter in transiently transfected isolated rat adipocytes or mature 3T3-L1 adipocytes, a potent inhibition of the activity of the FAS-chloramphenicol acetyltransferase reporter gene was observed by overexpression of Id2 or Id3. Reciprocally, co-transfection of Id3 antisense and ADD1 expression vectors in preadipocytes potentiated the ADD1/SREBP-1c effect on the FAS promoter activity. Finally, in the non adipogenic NIH-3T3 cell line, most of the ADD1-mediated trans-activation of the FAS promoter was counteracted by co-transfection of Id2 or Id3 expression vectors. Previous studies have indicated Id gene expression to be down-regulated during adipogenesis [Moldes, Lasnier, Fève, Pairault and Djian (1997) Mol. Cell. Biol. 17, 1796-1804]. We here demonstrated that there was a dramatic rise of Id2 and Id3 mRNA levels when 3T3-L1 adipocytes or isolated rat fat cells were exposed to lipolytic and anti-lipogenic agents, forskolin and isoproterenol. Taken together, our data show that Id products are functionally involved in modulating ADD1/SREBP-1c transcriptional activity, and thus lipogenesis in adipocytes.
Moldes
M
M
Université Pierre et Marie Curie, UPRES-A 7079 CNRS, Paris, France.
Boizard
M
M
Liepvre
X L
XL
Fève
B
B
Dugail
I
I
Pairault
J
J
D016475:3T3 Cells; D017667:Adipocytes; D000818:Animals; D022762:CCAAT-Enhancer-Binding Proteins; D002454:Cell Differentiation / Q000235:genetics; D000242:Cyclic AMP / Q000494:pharmacology; D004268:DNA-Binding Proteins / Q000037:antagonists & inhibitors* / Q000235:genetics; D064429:Fatty Acid Synthases / Q000235:genetics*; D015971:Gene Expression Regulation, Enzymologic; D017930:Genes, Reporter; D051798:Inhibitor of Differentiation Protein 1; D051797:Inhibitor of Differentiation Protein 2; D051796:Inhibitor of Differentiation Proteins; D051379:Mice; D009363:Neoplasm Proteins; D009687:Nuclear Proteins / Q000037:antagonists & inhibitors*; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D012097:Repressor Proteins; D015398:Signal Transduction / Q000235:genetics; D051780:Sterol Regulatory Element Binding Protein 1; D014157:Transcription Factors / Q000037:antagonists & inhibitors* / Q000235:genetics; D019014:fas Receptor / Q000235:genetics
D022762:CCAAT-Enhancer-Binding Proteins; D004268:DNA-Binding Proteins; C497454:ID1 protein, rat; C497451:Id2 protein, rat; C497455:Idb1 protein, mouse; C497452:Idb2 protein, mouse; D051798:Inhibitor of Differentiation Protein 1; D051797:Inhibitor of Differentiation Protein 2; D051796:Inhibitor of Differentiation Proteins; D009363:Neoplasm Proteins; D009687:Nuclear Proteins; D012333:RNA, Messenger; D012097:Repressor Proteins; C497388:Srebf1 protein, mouse; C497389:Srebf1 protein, rat; D051780:Sterol Regulatory Element Binding Protein 1; D014157:Transcription Factors; D019014:fas Receptor; C075640:ID3 protein, human; D000242:Cyclic AMP; D064429:Fatty Acid Synthases