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Expression of the vitamin D and the retinoid X receptors in Saccharomyces cerevisiae: alternative in vivo models for ligand-induced transactivation.

Abstract：

:The transcription factors of the nuclear hormone receptor family regulate gene expression via a complex network of macromolecular interactions. The ligand dependent activity of the vitamin D receptor is of particular interest because it modulates gene expression by the heterodimeric interaction with retinoid X receptors. We report here that individual functions of the vitamin D receptor including DNA-binding, homo- and heterodimerization and transactivation can be reconstituted in the yeast Saccharomyces cerevisiae. Interestingly, the simultaneous expression of the native vitamin D receptor and the retinoid X receptor beta resulted in a ligand independent transactivation of the lacZ reporter gene coupled to a mouse osteopontin vitamin D response element. However, homodimerization of the vitamin D receptor and heterodimerization were strongly enhanced upon ligand binding, when the receptors were expressed as fusion proteins with the Gal4 transcription factor in a yeast two-hybrid system. Furthermore, transactivating activity of a Gal4-fused vitamin D receptor was induced by vitamin D in a one-hybrid system devoid of retinoid X receptors. In addition, both Gal4-based systems behaved similar with regard to their dose-dependent response to vitamin D and related compounds when compared to the transcriptional activity of the vitamin D receptor in transiently transfected MCF-7 cells. Our results point out that specific ligands strongly enhanced receptor dimerization and induced transactivation in yeast and in MCF-7 cells. The constitutive transactivation by vitamin D receptor-retinoid X receptor heterodimers in yeast, depending on DNA binding of the receptors, strongly argues for the existence of cofactors, which are absent in yeast, but play a fundamental role in gene regulation in higher eukaryotic organisms.

journal_name

J Cell Biochem

journal_title

Journal of cellular biochemistry

authors

Berghöfer-Hochheimer Y,Zurek C,Langer G,Munder T

doi

10.1002/(sici)1097-4644(19970801)66:2<184::aid-jcb

subject

Has Abstract

pub_date

1997-08-01 00:00:00

pages

184-96

issue

eissn

0730-2312

issn

1097-4644

pii

10.1002/(SICI)1097-4644(19970801)66:2<184::AID-JCB

journal_volume

pub_type

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Expression of the vitamin D and the retinoid X receptors in Saccharomyces cerevisiae: alternative in vivo models for ligand-induced transactivation.