DNA BENDING IS INDUCED BY BINDING OF THE PEROXISOME PROLIFERATOR-ACTIVATED RECEPTOR GAMMA-2 HETERODIMER TO ITS RESPONSE ELEMENT IN THE MURINE LIPOPROTEIN-LIPASE PROMOTER

The peroxisome proliferator activated receptor gamma 2 (PPAR gamma 2) is a critical transcriptional regulator of adipogenesis. Lipoprotein l ipase is one of the earliest genes induced following exposure of pre-a dipocytes to PPAR gamma 2 ligands such as the thiazolidinediones. A un ique PPAR gamma 2 DNA recognition element was mapped to the region bet ween -171 to -149 bp of the murine LPL promoter, based on transfection analysis of deletion constructs and gel retention assays using bacter ially expressed, affinity purified recombinant proteins. Circular perm utation analysis determined that binding of the PPAR gamma 2/retinoic acid X receptor (RXR) heterodimer to its LPL promoter recognition elem ent induced DNA bending at an angle of approximately 46 degrees. Paral lel studies using an optimal PPAR recognition element obtained a compa rable bending angle of 56 degrees. This is the first demonstration tha t binding of a PPAR protein to its recognition element causes a distor tion of the DNA configuration. It indicates that PPAR gamma 2 utilizes a common mechanism shared by other nuclear hormone receptor proteins reported to induce bending at their DNA binding sites. (C) 1998 Academ ic Press.