INHIBITORS OF PREADIPOCYTE DIFFERENTIATION INDUCE COUP-TF BINDING TO A PPAR RXR BINDING SEQUENCE/

Inhibition of preadipocyte differentiation by 2,3,7,8 tetrachlorodiben zo-p-dioxin (TCDD) or retinoic acid (RA) identified another transcript ion factor which appears to be important for preadipocyte differentiat ion. Within 15 min of treating 3T3-L1 cells with TCDD, the aryl hydroc arbon receptor (AhR) is present within the cell nucleus, and increased binding of COUP-TF to an oligomer of the PPAR gamma 2/RXR binding seq uence (ARE7) occurs. Following 2 days of IW treatment, increased bindi ng of COUP-TF to the ARE7 oligomer also occurs. In untreated preadipoc ytes, COUP-TF mRNA increased at confluence and then decreased after in duction. TCDD treatment did not alter COUP-TF mRNA changes. Dephosphor ylating the nuclear extracts from TCDD and RA-treated cells eliminated binding of COUP-TF to ARE7. This is the first indication that COUP-TF may play a role in preadipocpte differentiation and that COUP-TF bind ing to DNA is correlated with TCDD and RA-induced phosphorylation. (C) 1996 Academic Press, Inc.