A negative coregulator for the human ER.

ERalpha is a ligand-activated transcription factor and a key regulator of the processes involved in cellular proliferation and differentiation. In addition, aberrant ERalpha activity is linked to several pathological conditions including breast cancer. A complex network of coregulatory proteins is largely believed to determine the transcriptional activity of ERalpha. We report here the isolation of a protein, denoted RTA for repressor of tamoxifen transcriptional activity, which contains an RNA recognition motif and interacts with the receptor N-terminal activation domain. RTA interacts with RNA in vitro, and its overexpression inhibits the partial agonist activity manifest by the antiestrogen tamoxifen while minimally affecting E2-activated transcription. Mutation of the RNA recognition motif alters RNA binding specificity and results in a dominant negative form of RTA that leads to derepression of ERalpha transcriptional activity, allowing all classes of antiestrogens to manifest partial agonist activity and enhancing agonist efficacy. These findings suggest a role for RNA binding proteins as coregulatory factors of the nuclear receptor family and reveal a novel mechanism by which antiestrogens can manifest agonist activities in some tissues.

[1]  Y. Sadovsky,et al.  Transcriptional activators differ in their responses to overexpression of TATA-box-binding protein , 1995, Molecular and cellular biology.

[2]  J. Polman,et al.  ERβ: Identification and characterization of a novel human estrogen receptor , 1996 .

[3]  V. Jordan.  The strategic use of antiestrogens to control the development and growth of breast cancer. , 1992, Cancer.

[4]  D. Fowlkes,et al.  Peptide antagonists of the human estrogen receptor. , 1999, Science.

[5]  D. McDonnell,et al.  The Molecular Pharmacology of SERMs , 1999, Trends in Endocrinology & Metabolism.

[6]  D. McDonnell,et al.  The Estrogen Receptor ␤-isoform (er␤) of the Human Estrogen Receptor Modulates Er␣ Transcriptional Activity and Is a Key Regulator of the Cellular Response to Estrogens and Antiestrogens* , 2022 .

[7]  B. O’Malley,et al.  Identification of a negative regulatory function for steroid receptors. , 1992, Proceedings of the National Academy of Sciences of the United States of America.

[8]  J. Hodgkin,et al.  Genetic and molecular analysis of fox-1, a numerator element involved in Caenorhabditis elegans primary sex determination. , 1999, Genetics.

[9]  C. Burd,et al.  RNA binding specificity of hnRNP A1: significance of hnRNP A1 high‐affinity binding sites in pre‐mRNA splicing. , 1994, The EMBO journal.

[10]  David M. Heery,et al.  A signature motif in transcriptional co-activators mediates binding to nuclear receptors , 1997, Nature.

[11]  R. Evans,et al.  Sharp, an inducible cofactor that integrates nuclear receptor repression and activation. , 2001, Genes & development.

[12]  B. Katzenellenbogen,et al.  William L. McGuire Memorial Lecture. Antiestrogens: mechanisms of action and resistance in breast cancer. , 1997, Breast cancer research and treatment.

[13]  H. Bryant,et al.  Raloxifene, tamoxifen, nafoxidine, or estrogen effects on reproductive and nonreproductive tissues in ovariectomized rats , 1996, FASEB journal : official publication of the Federation of American Societies for Experimental Biology.

[14]  W. Chin,et al.  Identification and Characterization of RRM-containing Coactivator Activator (CoAA) as TRBP-interacting Protein, and Its Splice Variant as a Coactivator Modulator (CoAM)* , 2001, The Journal of Biological Chemistry.

[15]  C. Allis,et al.  Steroid receptor coactivator-1 is a histone acetyltransferase , 1997, Nature.

[16]  S. Kerner,et al.  Identification of a third autonomous activation domain within the human estrogen receptor. , 1997, Molecular endocrinology.

[17]  T. Bourne,et al.  Effects of tamoxifen on uterus and ovaries of postmenopausal women in a randomised breast cancer prevention trial , 1994, The Lancet.

[18]  B. Katzenellenbogen,et al.  Antiestrogens: Mechanisms of action and resistance in breast cancer , 1997, Breast Cancer Research and Treatment.

[19]  B. Howard,et al.  The Transcriptional Coactivators p300 and CBP Are Histone Acetyltransferases , 1996, Cell.

[20]  R. Evans,et al.  The steroid and thyroid hormone receptor superfamily. , 1988, Science.

[21]  Zbigniew Dauter,et al.  Molecular basis of agonism and antagonism in the oestrogen receptor , 1997, Nature.

[22]  K. Ohe,et al.  Orphan Receptor DAX-1 Is a Shuttling RNA Binding Protein Associated with Polyribosomes via mRNA , 2000, Molecular and Cellular Biology.

[23]  D. Robyr,et al.  Nuclear hormone receptor coregulators in action: diversity for shared tasks. , 2000, Molecular endocrinology.

[24]  R B Mazess,et al.  Effects of tamoxifen on bone mineral density in postmenopausal women with breast cancer. , 1992, The New England journal of medicine.

[25]  B. O’Malley,et al.  Sequence and Characterization of a Coactivator for the Steroid Hormone Receptor Superfamily , 1995, Science.

[26]  C. Glass,et al.  Cloning and characterization of a corepressor and potential component of the nuclear hormone receptor repression complex. , 1997, Proceedings of the National Academy of Sciences of the United States of America.

[27]  P. Puigserver,et al.  Direct coupling of transcription and mRNA processing through the thermogenic coactivator PGC-1. , 2000, Molecular cell.

[28]  M. Tzukerman,et al.  Human estrogen receptor transactivational capacity is determined by both cellular and promoter context and mediated by two functionally distinct intramolecular regions. , 1994, Molecular endocrinology.

[29]  M. Stallcup,et al.  Enhancement of Estrogen Receptor Transcriptional Activity by the Coactivator GRIP-1 Highlights the Role of Activation Function 2 in Determining Estrogen Receptor Pharmacology* , 1998, The Journal of Biological Chemistry.

[30]  P. Chambon,et al.  Role of the two activating domains of the oestrogen receptor in the cell‐type and promoter‐context dependent agonistic activity of the anti‐oestrogen 4‐hydroxytamoxifen. , 1990, The EMBO journal.

[31]  D. Stillman,et al.  Ssn6-Tup1 interacts with class I histone deacetylases required for repression. , 2000, Genes & development.

[32]  B. Katzenellenbogen,et al.  Editorial: A New Actor in the Estrogen Receptor Drama-Enter ER-β. , 1997, Endocrinology.

[33]  L. Chin,et al.  Role for N-CoR and histone deacetylase in Sin3-mediated transcriptional repression , 1997, nature.

[34]  J. Gustafsson,et al.  Cloning of a novel receptor expressed in rat prostate and ovary. , 1996, Proceedings of the National Academy of Sciences of the United States of America.

[35]  C. Glass,et al.  A complex containing N-CoR, mSln3 and histone deacetylase mediates transcriptional repression , 1997, nature.

[36]  R. Evans,et al.  A transcriptional co-repressor that interacts with nuclear hormone receptors , 1995, Nature.

[37]  P. Meltzer,et al.  AIB1, a steroid receptor coactivator amplified in breast and ovarian cancer. , 1997, Science.

[38]  B. Katzenellenbogen,et al.  An estrogen receptor-selective coregulator that potentiates the effectiveness of antiestrogens and represses the activity of estrogens. , 1999, Proceedings of the National Academy of Sciences of the United States of America.

[39]  M. Swanson,et al.  hnRNP complexes: composition, structure, and function. , 1999, Current opinion in cell biology.

[40]  S. Pulst,et al.  A novel protein with RNA-binding motifs interacts with ataxin-2. , 2000, Human molecular genetics.

[41]  Neil J McKenna,et al.  A Steroid Receptor Coactivator, SRA, Functions as an RNA and Is Present in an SRC-1 Complex , 1999, Cell.

[42]  N. Weigel,et al.  The Nuclear Corepressors NCoR and SMRT Are Key Regulators of Both Ligand- and 8-Bromo-Cyclic AMP-Dependent Transcriptional Activity of the Human Progesterone Receptor , 1998, Molecular and Cellular Biology.

[43]  H. Samuels,et al.  PSF Is a Novel Corepressor That Mediates Its Effect through Sin3A and the DNA Binding Domain of Nuclear Hormone Receptors , 2001, Molecular and Cellular Biology.