The National Institute of Diabetes & Digestive & Kidney Diseases

The major focus of our studies is the initial events of steroid hormone action at a molecular level. These events include the equilibrium interactions of cofactors with agonist- and antagonist-bound receptors and the modulation of receptor-mediated gene transcription properties by novel pathways and cofactors. These studies involve cell-free and whole cell experiments with wild type and mutant receptors and cofactors. Some of the techniques used include standard luciferase activities in transfected cells, pulldown and co-immunoprecipitation assays, whole cell immunofluorescence, ChIP assays, and gene knockouts with siRNAs. Most studies utilize glucocorticoid (GR), progesterone (PR), or androgen receptor (AR) but others are employed as needed.

The dose-response curves of agonist complexes (or the concentration required for half of the maximal induction, i.e., EC50), and the partial agonist activity of antagonist complexes, have been shown to vary, even for the same gene in the same cell. These variations are of major importance for endocrine therapy and for differential control of gene expression by the single concentration of circulating steroid during development, differentiation, and homeostasis. These variations are also independent from changes in the total levels of gene activation and thus are proposed to proceed via a different mechanistic pathway. We have identified numerous components (a novel cis-acting element, coactivators, corepressors, Ubc9, Sur2 and increased concentrations of homologous receptor) that modulate the activities of GRs. Several of these factors also modulate the activities of PRs, ARs, mineralocorticoid receptors, and estrogen receptors. Thus, changes in EC50 and partial agonist activity may be a common phenomenon with all of the classical steroid receptors. Interestingly, the responses of GR and PR to the same factors can be opposite for the same gene in the same cell, thereby providing a clinically relevant mechanism for the different responses of a given cellular gene to a variety of steroid hormones. More recently, we have identified a novel protein (STAMP) that participates in the modulation of GR induction and repression properties. Domain mapping experiments, two-hybrid assays, pulldown assays, ChIP assays, avidin-biotin coupled DNA binding assays, siRNA knockout assays, and microarrays are being used to determine the crucial components for these responses and to identify downstream interacting factors. The molecular details and generality of these modulators of GR properties continue to be investigated with other steroid receptors.

He Y, Simons SS Jr STAMP, a novel predicted factor assisting TIF2 actions in glucocorticoid receptor-mediated induction and repression. Mol Cell Biol(27): 1467-85, 2007. [Full Text/Abstract]

Kim Y, Sun Y, Chow C, Pommier YG, Simons SS Jr Effects of acetylation, polymerase phosphorylation, and DNA unwinding in glucocorticoid receptor transactivation. J Steroid Biochem Mol Biol(100): 3-17, 2006. [Full Text/Abstract]

Simons SS Jr How much is enough? Modulation of dose-response curve for steroid receptor-regulated gene expression by changing concentrations of transcription factor. Curr Top Med Chem(6): 271-85, 2006. [Full Text/Abstract]

Wang D, Simons SS Jr Corepressor Binding to Progesterone and Glucocorticoid Receptors Involves the AF-1 Domain and Is Inhibited by Molybdate. Mol Endocrinol , 2005. [Full Text/Abstract]

Cho S, Kagan BL, Blackford JA Jr, Szapary D, Simons SS Jr Glucocorticoid receptor ligand binding domain is sufficient for the modulation of glucocorticoid induction properties by homologous receptors, coactivator transcription intermediary factor 2, and Ubc9. Mol Endocrinol (19): 290-311, 2005. [Full Text/Abstract]

Cho S, Blackford JA Jr, Simons SS Jr Role of activation function domain-1, DNA binding, and coactivator GRIP1 in the expression of partial agonist activity of glucocorticoid receptor-antagonist complexes. Biochemistry (44): 3547-61, 2005. [Full Text/Abstract]

Wang Q Blackford JA Jr Song LN Huang Y Cho S Simons SS Jr Equilibrium interactions of corepressors and coactivators with agonist and antagonist complexes of glucocorticoid receptors. Mol Endocrinol (18): 1376-95, 2004. [Full Text/Abstract]

Wang Q Anzick S Richter WF Meltzer P Simons SS Jr Modulation of transcriptional sensitivity of mineralocorticoid and estrogen receptors. J Steroid Biochem Mol Biol (91): 197-210, 2004. [Full Text/Abstract]

Chen J Blackford JA Jr Simons SS Jr PCR expression mutagenesis: a high-throughput mutation assay applied to the glucocorticoid receptor ligand-binding domain. Biochem Biophys Res Commun (321): 893-9, 2004. [Full Text/Abstract]

Chen J He Y Simons SS Jr Structure/activity relationships for GMEB-2: the second member of the glucocorticoid modulatory element-binding complex. Biochemistry (43): 245-55, 2004. [Full Text/Abstract]

Chen S Simons SS Jr A second pathway for modulating glucocorticoid receptor transactivation properties. Mol Cell Endocrinol (199): 129-42, 2003. [Full Text/Abstract]

Webster JI Tonelli LH Moayeri M Simons SS Jr Leppla SH Sternberg EM Anthrax lethal factor represses glucocorticoid and progesterone receptor activity. Proc Natl Acad Sci U S A (100): 5706-11, 2003. [Full Text/Abstract]

Anzick SL Azorsa DO Simons SS Jr Meltzer PS Phenotypic alterations in breast cancer cells overexpressing the nuclear receptor co-activator AIB1. BMC Cancer (3): 22, 2003. [Full Text/Abstract]

Simons SS Jr The importance of being varied in steroid receptor transactivation. Trends Pharmacol. Sci.(24): 253-259, 2003.

Murphy PJ Morishima Y Chen H Galigniana MD Mansfield JF Simons SS Jr Pratt WB Visualization and mechanism of assembly of a glucocorticoid receptor.Hsp70 complex that is primed for subsequent Hsp90-dependent opening of the steroid binding cleft. J Biol Chem (278): 34764-73, 2003. [Full Text/Abstract]

He Y Szapary D Simons SS Jr Modulation of induction properties of glucocorticoid receptor-agonist and -antagonist complexes by coactivators involves binding to receptors but is independent of ability of coactivators to augment transactivation. J Biol Chem (277): 49256-66, 2002. [Full Text/Abstract]

Kaul S Murphy PJ Chen J Brown L Pratt WB Simons SS Jr Mutations at positions 547-553 of rat glucocorticoid receptors reveal that hsp90 binding requires the presence, but not defined composition, of a seven-amino acid sequence at the amino terminus of the ligand binding domain. J Biol Chem (277): 36223-32, 2002. [Full Text/Abstract]

Chen J Kaul S Simons SS Jr Structure/activity elements of the multifunctional protein, GMEB-1. Characterization of domains relevant for the modulation of glucocorticoid receptor transactivation properties. J Biol Chem (277): 22053-62, 2002. [Full Text/Abstract]

Kaul S Blackford JA Jr Cho S Simons SS Jr Ubc9 is a novel modulator of the induction properties of glucocorticoid receptors. J Biol Chem (277): 12541-9, 2002. [Full Text/Abstract]

Zeng H Kaul S Simons SS Jr Genomic organization of human GMEB-1 and rat GMEB-2: structural conservation of two multifunctional proteins. Nucleic Acids Res (28): 1819-29, 2000. [Full Text/Abstract]