ISSN:
0730-2312
Keywords:
vitamin D receptor
;
retinoid X receptor
;
transactivation systems
;
vitamin D regulation
;
Saccharomyces cerevisiae
;
Life and Medical Sciences
;
Cell & Developmental Biology
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Biology
,
Chemistry and Pharmacology
,
Medicine
Notes:
The transcription factors of the nuclear hormone receptor familiy 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 β 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. J. Cell. Biochem. 66:184-196, 1997. © 1997 Wiley-Liss, Inc.
Additional Material:
5 Ill.
Type of Medium:
Electronic Resource
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