A novel intronic peroxisome proliferator-activated receptor gamma enhancer in the uncoupling protein (UCP) 3 gene as a regulator of both UCP2 and -3 expression in adipocytes.
Uncoupling Proteins (UCPs) are integral ion channels residing in the inner mitochondrial membrane. UCP2 is ubiquitously expressed, while UCP3 is found primarily in muscles and adipose tissue. Although the exact molecular mechanism of action is controversial, it is generally agreed that both homologues function to facilitate mitochondrial fatty acid oxidation. UCP2 and -3 expression is activated by the peroxisome proliferator-activated receptors (PPARs), but so far no PPAR response element has been reported in the vicinity of the Ucp2 and Ucp3 genes. Using genome-wide profiling of PPARgamma occupancy in 3T3-L1 adipocytes we demonstrate that PPARgamma associates with three chromosomal regions in the vicinity of the Ucp3 locus and weakly with a site in intron 1 of the Ucp2 gene. These sites are isolated from the nearest neighboring sites by >900 kb. The most prominent PPARgamma binding site in the Ucp2 and Ucp3 loci is located in intron 1 of the Ucp3 gene and is the only site that facilitates PPARgamma transactivation of a heterologous promoter. This site furthermore transactivates the endogenous Ucp3 promoter, and using chromatin conformation capture we show that it loops out to specifically interact with the Ucp2 promoter and intron 1. Our data indicate that PPARgamma transactivation of both UCP2 and -3 is mediated through this novel enhancer in Ucp3 intron 1.
Bugge
Anne
A
Department of Biochemistry and Molecular Biology, University of Southern Denmark, Campusvej 55, 5230 Odense M, Denmark.
Siersbaek
Majken
M
Madsen
Maria S
MS
Göndör
Anita
A
Rougier
Carole
C
Mandrup
Susanne
S
D041721:3T3-L1 Cells; D017667:Adipocytes / Q000166:cytology / Q000378:metabolism*; D000818:Animals; D002843:Chromatin / Q000737:chemistry; D004742:Enhancer Elements, Genetic; D006801:Humans; D007438:Introns; D007473:Ion Channels / Q000378:metabolism*; D051379:Mice; D024101:Mitochondrial Proteins / Q000378:metabolism*; D047495:PPAR gamma / Q000235:genetics* / Q000378:metabolism; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D012190:Retroviridae / Q000235:genetics; D015533:Transcriptional Activation; D000071246:Uncoupling Protein 2; D000071247:Uncoupling Protein 3
D002843:Chromatin; D007473:Ion Channels; D024101:Mitochondrial Proteins; D047495:PPAR gamma; C000604389:UCP2 protein, human; C000604392:UCP3 protein, human; C000604390:Ucp2 protein, mouse; C000604393:Ucp3 protein, mouse; D000071246:Uncoupling Protein 2; D000071247:Uncoupling Protein 3