RSUME Enhances Glucocorticoid Receptor SUMOylation and Transcriptional Activity

Abstract

Glucocorticoid receptor (GR) activity is modulated by posttranslational modifications, including phosphorylation, ubiquitination, and SUMOylation. The GR has three SUMOylation sites: lysine 297 (K297) and K313 in the N-terminal domain (NTD) and K721 within the ligand-binding domain. SUMOylation of the NTD sites mediates the negative effect of the synergy control motifs of GR on promoters with closely spaced GR binding sites. There is scarce evidence on the role of SUMO conjugation to K721 and its impact on GR transcriptional activity. We have previously shown that RSUME (RWD-containing SUMOylation enhancer) increases protein SUMOylation. We now demonstrate that RSUME interacts with the GR and increases its SUMOylation. RSUME regulates GR transcriptional activity and the expression of its endogenous target genes, FKBP51 and S100P. RSUME uncovers a positive role for the third SUMOylation site, K721, on GR-mediated transcription, demonstrating that GR SUMOylation acts positively in the presence of a SUMOylation enhancer. Both mutation of K721 and small interfering RNA-mediated RSUME knockdown diminish GRIP1 coactivator activity. RSUME, whose expression is induced under stress conditions, is a key factor in heat shock-induced GR SUMOylation. These results show that inhibitory and stimulatory SUMO sites are present in the GR and at higher SUMOylation levels the stimulatory one becomes dominant.

SUPPLEMENTAL MATERIAL

Supplemental material for this article may be found at http://dx.doi.org/10.1128/MCB.01470-12.

ACKNOWLEDGMENTS

This work was supported by grants from the Max Planck Society, Germany; the University of Buenos Aires; CONICET; the Agencia Nacional de Promoción Científica y Tecnológica, Argentina; the National Institutes of Health (R56DK061656 to J.A.I.-L.); and FOCEM-Mercosur (COF 03/11). Jimena Druker is a postdoctoral fellow of the Bunge & Born Foundation, Argentina.

We thank Ronald Hay, Jorma Palvimo, Michael Stallcup, Mary Dasso, and Dietmar Spengler for providing the plasmids and antibodies used in this work and Federico Pelisch for technical comments and discussion of the manuscript.