DIVERSE PEROXISOME PROLIFERATOR-ACTIVATED RECEPTORS BIND TO THE PEROXISOME PROLIFERATOR-RESPONSIVE ELEMENTS OF THE RAT HYDRATASE DEHYDROGENASE AND FATTY ACYL-COA OXIDASE GENES BUT DIFFERENTIALLY INDUCE EXPRESSION
Sl. Marcus et al., DIVERSE PEROXISOME PROLIFERATOR-ACTIVATED RECEPTORS BIND TO THE PEROXISOME PROLIFERATOR-RESPONSIVE ELEMENTS OF THE RAT HYDRATASE DEHYDROGENASE AND FATTY ACYL-COA OXIDASE GENES BUT DIFFERENTIALLY INDUCE EXPRESSION, Proceedings of the National Academy of Sciences of the United Statesof America, 90(12), 1993, pp. 5723-5727
The ability of peroxisome proliferator-activated receptors (PPARs) to
induce expression of a reporter gene linked to a peroxisome proliferat
or-responsive element (PPRE) from either the rat enoyl-CoA hydratase/3
-hydroxyacyl-CoA dehydrogenase gene or acyl-CoA oxidase [acyl-CoA: oxy
gen 2-oxidoreductase, EC 1.3.3.6] gene was examined by transient trans
fection assays in COS cells. Mouse and rat PPARs, as well as Xenopus P
PARalpha (xPPARalpha) could induce expression of a reporter gene linke
d to the hydratase/dehydrogenase PPRE in the presence of the peroxisom
e proliferators ciprofibrate or Wy-14,643, whereas xPPARbeta and xPPAR
gamma were ineffective. A similar induction of expression of a reporte
r gene linked to the acyl-CoA oxidase PPRE was observed with all PPARs
except xPPARbeta. Extracts from cells transfected with PPAR-encoding
genes contained factors that bound to both PPREs. In vitro synthesized
PPARs could interact weakly with both PPREs; however, binding of each
PPAR to both PPREs was significantly increased by the addition of COS
cell nuclear extracts, demonstrating that efficient PPAR/DNA binding
requires auxiliary cofactors. One cofactor was identified as the 9-cis
-retinoic acid receptor, RXRalpha (retinoid X receptor alpha). Coopera
tive DNA binding and heteromerization between RXRalpha and each of the
PPARs could be seen with both PPREs. Our results demonstrate that PPA
R/PPRE binding and cooperativity with RXRalpha (and other cofactors) a
re obligatory but not necessarily sufficient for peroxisome proliferat
or-dependent transcription induction and that distinct PPREs can selec
tively mediate induction by particular PPARs.