Subtype- and response element-dependent differences in transactivation by peroxisome proliferator-activated receptors alpha and gamma.
Peroxisome proliferator-activated receptors (PPAR) modulate transcription by binding to specific peroxisome proliferator-response elements (PPRE) through heterodimerization with the 9-cis retinoic acid receptor (RXR). To investigate potential subtype- and response element-dependent differences in transcriptional activation by PPARs, we expressed PPARalpha or PPARgamma2, along with RXRalpha, in the yeast Saccharoromyces cerevisiae and compared their ability to activate transcription of reporter genes containing a PPRE from either the rat acyl-CoA oxidase (AOx) or hydratase-dehydrogenase (HD) gene. PPARgamma2 and RXRalpha, when coexpressed from low copy vectors, potently and synergistically activated transcription of the AOx-PPRE reporter gene, but only weakly stimulated transcription of the HD-PPRE reporter gene. This response element preference, which was also observed in mammalian cells, could not be attributed to differences in binding affinity of PPARgamma2/RXRalpha heterodimers to these elements in vitro. Interestingly, PPARgamma2 expressed from a high copy vector was able to strongly activate transcription of the HD-PPRE reporter gene, even in the absence of coexpressed RXRalpha. In comparison to the findings with PPARgamma2, the HD-PPRE served as a significantly more robust response element for PPARalpha as compared to the AOx-PPRE. PPRE-dependent transcriptional activation by PPARalpha correlated with binding efficiencies of PPARalpha/RXRalpha to the response element. Our findings demonstrate that the transactivation potential of PPAR subtypes can be differentially modulated by distinct PPREs.
Department of Cell Biology and Anatomy, University of Alberta, Edmonton, Canada.
A
A
Kassam
J
J
Hunter
R A
RA
Rachubinski
J P
JP
Capone
D042962:Acyl-CoA Oxidase; D000818:Animals; D001667:Binding, Competitive; D002460:Cell Line; D004268:DNA-Binding Proteins / Q000235:genetics; D019281:Dimerization; D004591:Electrophoresis, Polyacrylamide Gel; D018628:Gene Dosage; D017930:Genes, Reporter; D051379:Mice; D009841:Oligonucleotides; D010088:Oxidoreductases / Q000235:genetics; D020025:Peroxisome Proliferators / Q000378:metabolism*; D011401:Promoter Regions, Genetic / Q000235:genetics; D051381:Rats; D018160:Receptors, Cytoplasmic and Nuclear / Q000235:genetics / Q000378:metabolism*; D018168:Receptors, Retinoic Acid / Q000235:genetics; D011994:Recombinant Proteins / Q000378:metabolism; D020218:Response Elements / Q000235:genetics*; D047488:Retinoid X Receptors; D012441:Saccharomyces cerevisiae / Q000235:genetics; D029701:Saccharomyces cerevisiae Proteins; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D015533:Transcriptional Activation / Q000235:genetics*; D014162:Transfection
D004268:DNA-Binding Proteins; D009841:Oligonucleotides; D020025:Peroxisome Proliferators; D018160:Receptors, Cytoplasmic and Nuclear; D018168:Receptors, Retinoic Acid; D011994:Recombinant Proteins; D047488:Retinoid X Receptors; D029701:Saccharomyces cerevisiae Proteins; D014157:Transcription Factors; D010088:Oxidoreductases; D042962:Acyl-CoA Oxidase; C467991:POX1 protein, S cerevisiae