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Mol. Cell. Biol. doi:10.1128/MCB.01140-07
Copyright (c) 2007, American Society for Microbiology and/or the Listed Authors/Institutions. All Rights Reserved.

Functional Conservation of the Glutamine-Rich Domains of Yeast Gal11 and Human SRC-1 in the Transactivation of Glucocorticoid Receptor Tau 1 in Yeast

Hormone Research Center, School of Biological Sciences and Technology, Chonnam National University, Gwangju 500-757, South KOREA

^* To whom correspondence should be addressed. Email: yclee{at}jnu.ac.kr.

	Abstract

The yeast Gal11 protein, a component of the Mediator complex, is required for the transcriptional activation of many class II genes as a physiological target of various activator proteins in vivo. In this study, we identified the yeast Mediator complex as a novel coactivator of the transcriptional activity of the glucocorticoid receptor (GR) tau 1 (1), the major transcriptional activation domain of the GR. GR 1 directly interacted with the Mediator complex in vivo and in vitro in a Gal11 module-dependent manner and the Gal11p subunit interacted directly with GR 1. Specific amino acid residues within the glutamine rich (Qr) domain of Gal11p (residues 116-277) were essential for its interaction with GR 1 and GR 1 transactivity in yeast, as demonstrated by mutational analysis of Gal11 Qr domain which is highly conserved among human steroid receptor coactivator (SRC) proteins. A Gal11p variant, mini-Gal11p, comprised of the Mediator-association and Qr domains of Gal11p, or chimeric mini-Gal11p containing the Qr domain of SRC-1, could potentiate the GR 1 transactivity in a gal11 yeast strain. These results suggest that there is functional conservation between Qr domains of yeast Gal11p and mammalian SRC proteins as direct targets of activator proteins in yeast.