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

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

Received 27 June 2007/ Returned for modification 1 August 2007/ Accepted 14 November 2007

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 (Saccharomyces cerevisiae) 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 to 277) were essential for its interaction with GR 1 and GR 1 transactivity in yeast, as demonstrated by mutational analysis of the 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.

Published ahead of print on 10 December 2007.