CLONING AND IDENTIFICATION OF RAT DEOXYURIDINE TRIPHOSPHATASE AS AN INHIBITOR OF PEROXISOME PROLIFERATOR-ACTIVATED RECEPTOR-ALPHA

Peroxisome proliferator-activated receptors (PPARs) are members of the nuclear receptor superfamily that transcriptionally regulate responsi ve genes by binding to the peroxisome proliferator response elements, Protein(s) interacting with PPAR, isoforms (alpha, delta, and gamma) m ay modulate the PPAR-mediated transcriptional activation, Using a yeas t two-hybrid system to screen a rat liver cDNA library, we have identi fied rat deoxyuridine-triphosphatase (dUTPase, EC 3.6.1.23) as a PPAR alpha-interacting protein, This cDNA encodes a polypeptide of 203 amin o acids; the C-terminal 141-amino acid segment of this protein corresp onds to the full-length human enzyme, which exhibits 92% identity with human dUTPase; the N-terminal extra Ga-amino acid residue region is a rginine-rich, In vitro binding assays indicate that rat dUTPase intera cts with all three isoforms of mouse PPAR, but not with retinoid X rec eptor and thyroid hormone receptor, Interaction of PPAR alpha with dUT Pase is with the N-terminal fia-amino acid segment of rat dUTPase, Ful l-length rat dUTPase prevents PPAR-retinoid X receptor heterodimerizat ion resulting in an inhibition of PPAR activity in a ligand-independen t manner. Immunostaining of human kidney tsA201 cells, transiently exp ressing dUTPase showed that this protein is present predominantly in t he cytoplasm but translocates into the nucleus with PPAR alpha when PP AR alpha is coexpressed with dUTPase, Northern blot hybridization show s that rat dUTPase is encoded by an abundant 1-kilobase mRNA species p resent in all rat tissues, The identification of dUTPase as a PPAR-int eracting protein suggests a possible link between tumorigenic peroxiso me proliferators and the enzyme system involved in the maintenance of DNA fidelity.