Amino acid residues in both the DNA-binding and ligand-binding domains influence transcriptional activity of the human peroxisome proliferator-activated receptor alpha

We have investigated the basis of the lack of activity of a natural variant human peroxisome proliferator-activated receptor alpha, hPPAR alpha 6/29. A subcloning approach was used to change the four variant amino acids in the hPPAR alpha 6/29 sequence, individually and in combination, to those found in an active human PPAR alpha. Individual amino acid ''back mutations'' were unable to confer on hPPAR alpha 6/29 the ability to be activated by peroxisome proliferators in a transient transfection assay. Although hPPAR alpha 6/29 was able to bind specifically to DNA in the presence of the retinoid X receptor alpha (RXR alpha), the complete restoration of receptor transcriptional activity required two separate back mutations of the hPPAR alpha 6/29 sequence, namely amino acid 123 in the DNA binding domain, and amino acid 444 close to the C-terminus. This suggests that sequences in the PPAR alpha DNA binding domain influence other receptor functions besides DNA binding. (C) 1997 Academic Press.