ABSTRACT
Attempts to discover a hepatic cell component capable of binding peroxisome proliferators and to control gene activation were begun several years ago. There were several controversial factors: the isolation of a cytosolic nafenopin binding protein by Reddy’s group (Lalwani et al., 1987), the identification of albumin as a candidate (Milton et al., 1988), and the discovery of a 70 kD heat shock protein (HSP 70) by Alvarez et al. (1990). Recently, Issemann and Green (1990) have cloned from mouse liver, a nuclear receptor for the steroid receptor superfamily which responds to peroxisome proliferators (termed ‘peroxisome proliferator associated receptor’ (PPAR)), but they reported weak (or no) affinity for ligand binding. However, Green’s group Tugwood et al., 1992 has recently shown that PPAR is a trans effector able to bind to the - 560 region of the 5' upstream sequence of the mouse liver acyl-CoA oxidase gene. PPAR may also regulate the P4504A1 gene (Green, S., personal communication). In this context, it has also been shown that the dexamethasone receptor can regulate both cell growth and peroxisomal ßoxidation in cultured 7800C1 hepatoma cells (Sørensen et al., 1990).
