Thomas G Boyer
University Of Texas Hlth Sci Ctr San Ant
Project start date: 2009-04-07
Project end date: 2014-01-31
Sponsored Links Excellgen http://Excellgen.com
Grants awarded to Thomas G Boyer
Mediator And Epigenetic Control Of Neuronal Gene Expression And Differentiation
Thomas G Boyer, Associate Professor
Molecular Medicineuniversity Of Texas Hlth Sci Ctr San Ant
Grant 1R01MH085320-01A1 from National Institute Of Mental Health IRG: ZRG1
Abstract: provided by investigator) Our long-term goal is to understand the role and regulation of Mediator in the control of gene expression and cell fate specification within the vertebrate central nervous system. Mediator is a multiprotein interface between gene-specific transcription factors and the eukaryotic RNA polymerase II general transcription machinery. In this capacity, Mediator serves to channel regulatory signals from activator and repressor proteins to affect changes in gene expression programs that control diverse physiological processes, including cell growth and homeostasis, development, and differentiation. MED12, an Xq13-encoded 230 kDa Mediator subunit, plays an essential role in neuronal development through selective regulation of neuronal gene expression. Genetic variation in MED12 has been linked to neuropsychiatric illness and X-linked mental retardation (XLMR). However, the molecular bases by which MED12 controls neuronal differentiation through selective gene regulation and the means by which pathologic sequence alterations impact MED12 function leading to behavioral and cognitive defects remain to be clarified. In this regard, we recently identified a functional interaction between the MED12 interface in Mediator and G9a histone methyltransferase required for epigenetic silencing imposed by the RE1 silencing transcription factor/neuron restrictive silencing factor (REST/NRSF), a key determinant of neuronal fate that suppresses neuronal gene expression in non-neuronal and neural progenitor cells. Notably, we found that missense mutations in MED12 responsible for two XLMR disorders, FG syndrome and Lujan syndrome, disrupt its REST-specific corepressor function, thus linking REST-dependent neuronal gene repression with higher-order cognitive function in humans. Because our recent studies implicate REST-dependent neuronal gene repression in epigenetic restriction of neural progenitor cell differentiation, our findings provide a possible epigenetic perspective to explain the role of MED12 in the etiology of XLMR through altered neuronal development. Thus, we hypothesize that XLMR- associated mutations in MED12 disrupt REST-imposed epigenetic restrictions on neuronal gene expression and neural progenitor cell differentiation. To provide support for this hypothesis, we propose the following aims to decipher the role and pathologic implications of MED12/Mediator in REST-dependent epigenetic suppression of neuronal gene expression and differentiation (1) Elucidate the mechanistic basis of MED12/Mediator in REST-dependent extra-neuronal gene silencing; (2) Elucidate the role and regulation of MED12/Mediator in REST-dependent suppression of neuronal gene expression and differentiation in neural progenitor cells; (3) Elucidate the impact and mechanism of XLMR-associated mutations in MED12 on REST- dependent suppression of neuronal gene expression and differentiation in neural progenitor cells. We expect these studies to have important human health implications for cell replacement therapy in neurological disease as well as the etiology of XLMR. We expect these studies to have important implications for cell replacement therapy in neurological disease as well as the etiology of developmental and cognitive defects in humans. First, studies proposed herein to elucidate the mechanism (Aim 1) and regulation (Aim 2) of MED12/Mediator in control of neuronal gene expression and differentiation are expected to break new ground and illuminate fundamental aspects of neural stem cell biology that will be essential to guide prospective cell-based therapeutic approaches to repopulate damaged or diseased areas of the nervous system. Second, studies proposed herein to evaluate the impact of XLMR-associated mutations in MED12 on its basic biochemical properties and functional interactions relevant to neuronal gene repression and neural stem cell differentiation (Aim 3) should reveal new mechanistic insight concerning the etiology of XLMR and possibly identify new avenues for therapeutic or remedial intercession
Project start date: 2009-04-07
Project end date: 2014-01-31
Modulation Of Estrogen Receptor Function By BRCA1
Thomas G Boyer, Associate Professor
University Of Texas Hlth Sci Ctr San Ant San Antonio, Tx 78229
Grant 5R01CA098301-05 from National Cancer Institute IRG: REN
Abstract: Our long-term goal is to understand how inactivation of the breast cancer susceptibility gene, BRCA1, leads to breast tumorigenesis. At the cellular level, BRCA1 ensures global genome stability by coupling DNA damage-induced signals to downstream responses, including DNA damage repair and cell-cycle checkpoint activation. Because the DNA damage-induced signaling pathways that converge on BRCA1 are conserved in most cell types, BRCA1 is likely to function ubiquitously in the maintenance of genome integrity. Nonetheless, germline inactivation of BRCA1 leads principally to cancer of the breast and ovary, and the underlying basis for its tissue-restricted tumor suppressor function remains poorly defined. Recently, we discovered a novel function for BRCA1 in suppressing the ligand-independent transcriptional activity of the estrogen receptor alpha (ERalpha), a principal determinant of the growth and differentiation of breasts and ovaries. Importantly, we showed that clinically validated BRCA1 missense mutations abrogate this repression activity, suggesting that its ERalpha-specific repression function is important for the biological activity of BRCA1 in breast and ovarian tumor suppression. In human breast cancer cells, we observed an association between BRCA1 and ERalpha at endogenous estrogen-responsive gene promoters before, but not after, estrogen stimulation. Furthermore, we demonstrated that forced reduction of BRCA1 in estrogen-dependent human ovarian cancer cells could be correlated with increases in both the estrogen-independent transcription of ERalpha-target genes and estrogen-independent proliferation. We therefore hypothesize that BRCA1 represents a ligand-reversible barrier to transcriptional activation by unliganded ERalpha, and further, that mutational inactivation of BRCA1 promotes breast and ovarian epithelial cell proliferation through aberrant expression of estrogen-responsive genes. To confirm and extend this hypothesis, we propose the following aims. Aim 1 is to elucidate the mechanism by which BRCA1 represses the ligand-independent transcriptional activity of ERalpha. Aim 2 is to characterize the regulation of BRCA1-mediated ERalpha repression by both estrogen-dependent and estrogen-independent cell signals. Aim 3 is to establish the biological role of BRCA1 in the control of cellular proliferation through modulation of ligand-independent ERalpha activity. These studies should reveal novel insight into the tissue-specific tumor suppressor function of BRCA1 and provide defined molecular targets for future intervention in breast cancer.
Keywords: brca gene, breast neoplasm, estrogen receptor, gene induction /repression, genetic regulation, neoplastic transformation, protein structure function, receptor expression, biological signal transduction, cell proliferation, estrogen, ligand, neoplasm /cancer genetics, receptor binding, cell line, female, genetically modified animal, laboratory mouse, women s health
Project start date: 2003-04-01
Project end date: 2008-03-31
5R01CA098301-05 (2007): $230147
5R01CA098301-04 (2006): $237021
5R01CA098301-03 (2005): $242725
5R01CA098301-02 (2004): $240540
Thomas G Boyer
University Of Texas Hlth Sci Ctr San Ant
Project start date: 2008-04-01
Project end date: 2013-03-31