An intact DNA-binding domain is not required for peroxisome proliferator-activated receptor gamma (PPARgamma) binding and activation on some PPAR response elements.
Peroxisome proliferator-activated receptor gamma (PPARgamma) interacts with retinoid X receptor (RXR) on PPAR response elements (PPREs) to regulate transcription of PPAR-responsive genes. To investigate the binding of PPARgamma and RXR to PPREs, three mutations were constructed in the DNA-binding domains of PPARgamma; two of the mutants maintained the structure of zinc finger I (PPARgamma-GS and PPARgamma-AA), and a third mutation disrupted the protein structure of zinc finger I (PPARgamma-CS). Results indicated that the mutations of PPARgamma that maintained intact zinc fingers were capable of binding to a variety of PPREs in the presence of RXR and could activate transcription on several PPREs. In parallel, a mutation was created in the DNA-binding domain of RXRalpha that maintained the structure of the zinc fingers (RXR-GS) but did not bind DNA and was transcriptionally inactive. Examination of the 3' half-site of several PPREs revealed that variations from the consensus sequence reduced or abolished transcriptional activity, but conversion to consensus improved transcriptional activity with PPARgamma-GS and PPARgamma-AA. Examination of the 5' half-site indicated that the upstream three nucleotides were more important for transcriptional activity than the downstream three nucleotides. Our data demonstrated that stringent binding of RXR to the 3' half-site of a PPRE is more influential on the binding of the PPARgamma/RXR heterodimer than the ability of PPARgamma to bind DNA. Thus, unlike RXR, PPARgamma exhibits promiscuity in binding on a PPRE, suggesting that the definition of a PPRE for PPARgamma may need to be expanded.
Temple
Karla A
KA
Department of Medicine, and Committee on Molecular Metabolism and Nutrition, Pritzker School of Medicine, University of Chicago, Chicago, Illinois 60637, USA.
Cohen
Ronald N
RN
Wondisford
Sarah R
SR
Yu
Christine
C
Deplewski
Dianne
D
Wondisford
Fredric E
FE
D042962:Acyl-CoA Oxidase / Q000235:genetics; D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D016384:Consensus Sequence; D019281:Dimerization; D051379:Mice; D008969:Molecular Sequence Data; D016296:Mutagenesis; D047495:PPAR gamma / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D010729:Phosphoenolpyruvate Carboxykinase (GTP) / Q000235:genetics; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D020218:Response Elements / Q000502:physiology*; D047488:Retinoid X Receptors / Q000378:metabolism; D015533:Transcriptional Activation / Q000502:physiology*; D014162:Transfection
D047495:PPAR gamma; D047488:Retinoid X Receptors; D042962:Acyl-CoA Oxidase; D010729:Phosphoenolpyruvate Carboxykinase (GTP)