The human uncoupling protein-3 gene. Genomic structure, chromosomal localization, and genetic basis for short and long form transcripts.

Uncoupling protein-3 (UCP3) is a recently identified candidate mediator of adaptive thermogenesis in humans. Unlike UCP1 and UCP2, UCP3 is expressed preferentially and at high levels in human skeletal muscle and exists as short and long form transcripts, UCP3S and UCP3L. UCP3S is predicted to encode a protein which lacks the last 37 C-terminal residues of UCP3L. In the present study, we have defined the intron-exon structure for the human UCP3 gene and determined that UCP3S is generated when a cleavage and polyadenylation signal (AATAAA) located in the last intron prematurely terminates message elongation. In addition we have mapped UCP3 to the distal segment of human chromosome 11q13 (between framework markers D11S916 and D11S911), adjacent to UCP2. Of note, UCP2 and UCP3 in both mice and humans colocalize in P1 and BAC genomic clones indicating that these two UCPs are located within 75-150 kilobases of each other and most likely resulted from a gene duplication event. Previous studies have noted that mouse UCP2 maps to a region of chromosome 7 which is coincident with three independently mapped quantitative trait loci for obesity. Our study shows that UCP3 is also coincident with these quantitative trait loci raising the possibility that abnormalities in UCP3 are responsible for obesity in these models.