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Nuclear receptors (NRs) are ligand-regulated, DNA-binding transcription factors that function in the chromatin environment of the nucleus to alter the expression of subsets of hormone-responsive genes. It is clear that chromatin, rather than being a passive player, has a profound effect on both transcriptional repression and activation mediated by NRs. NRs act in conjunction with at least three general classes of cofactors to regulate transcription in the context of chromatin: (a) chromatin remodelers; (b) corepressors; and (c) coactivators, many of which have distinct enzymatic activities that remodel nucleosomes or covalently modify histones (e.g. acetylases, deacetylases, methyltransferases, and kinases) | Eur. J. Biochem. 269 2275-2283 2002 FEBS 2002 doi 10.1046 j.1432-1033.2002.02889.x MINIREVIEW Nuclear receptor-dependent transcription with chromatin Is it all about enzymes W Lee Kraus1 2 and Jiemin Wong3 1 Department of Molecular Biology and Genetics Cornell University Ithaca NY USA department of Pharmacology Weill Medical College of Cornell University New York USA 3Department of Molecular and Cellular Biology Baylor College of Medicine One Baylor Plaza Houston TX USA Nuclear receptors NRs are ligand-regulated DNA-bind-ing transcription factors that function in the chromatin environment of hie nicleis to alter tire expression of subsets of homoonÉ -es soosi r e genes. It ss dear hliat chrmntinn rather than being a passive player has a profound effect on both transcriptional repression and activation mediated by NRs. NRs act in conjunction with at least three general classes of col ccorss to reuLileOi -1X11000110011 in the 1111x11 of chromatin a chromatin remodelers b corepressors and c coactivators many of tiiidi aave distinct enymnatic activities that remodel nucleosomes or covalently modify histones e.g. acetylases deacetylases methyltransferases and kinases . In this paper we will present a brief overview of these enzymes their activities and how they assist NRs in the repression or activation of transcri piion in the context of chromatin. Keywords chromatin chromatin remodeling coactivators corepressors histone acetyltransferase histone deacetylase histone kinase histone methyltransferase nuclear receptor transcription. INTRODUCTION Nuclear receptors NRs comprise a large superfamily of DNA-binding transcriptional regulatory proteins that control the expression of distinct unbsets of genet ilt the chromatin environment of the nudeus 11-3 . in many t e the activities of the recepo-ss are niCKhlaiO d by the binding of hormonal la rmds e.g. lterotds eetinotds thoroid hormone and vitamin D3 which function as key regulators in numerous physiological processes e.g.