Michael J Garabedian

NYU Langone Medical Center, New York, New York, United States

Are you Michael J Garabedian?

Claim your profile

Publications (102)613.82 Total impact

  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: In mouse models of atherosclerosis, normalization of hyperlipidemia promotes macrophage emigration and regression of atherosclerotic plaques in part by the Liver X Receptor (LXR)-mediated induction of the chemokine receptor CCR7. Here we report that LXRα serine 198 (S198) phosphorylation modulates CCR7 expression. Low levels of S198 phosphorylation are observed in plaque macrophages in the regression environment where high levels of CCR7 expression are observed. Consistent with these findings, CCR7 gene expression in human and mouse macrophages cell lines is induced when LXRα at S198 is non-phosphorylated. In bone marrow derived-macrophages (BMDMs) we also observe induction of CCR7 by ligands that promote non-phosphorylated LXRα S198 and this is lost in LXR deficient BMDMs. LXRα occupancy at the CCR7 promoter is enhanced and histone modifications associated with gene repression are reduced in RAW264.7 cells expressing non-phosphorylated (RAW-LXRαS198A) compared to phosphorylated LXRα (RAW-LXRαWT). Expression profiling from ligand treated RAW-LXRαS198A compared to RAW-LXRαWT cells revealed induction of cell migratory and anti-inflammatory genes, and repression of pro-inflammatory genes. Modeling of LXRα S198 in non-phosphorylated and phosphorylated states identified phosphorylation-dependent conformational changes in the hinge region commensurate with sites for protein interaction. Therefore, gene transcription is regulated by LXRα S198 phosphorylation including anti-atherogenic genes like CCR7.
    Molecular and Cellular Biology 06/2015; 35(11):2024-2034. DOI:10.1128/MCB.00985-14 · 5.04 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Objective. To provide the otolaryngologist an evidence-based sound review of glucocorticoid use for laryngeal pathology. Data Sources. Contemporary peer-reviewed literature as well as review articles. Review Methods. A review of the literature regarding glucocorticoids as a therapeutic intervention for the treatment of benign laryngeal pathology, as well as laryngeal manifestations of systemic disease was performed. Review includes both systemic administration as well as local injection. Results. Glucocorticoids, administered in the critical care setting for planned extubation, markedly reducing the risk of re-intubation and remain a rudimentary pharmacologic adjunct in laryngeal manifestations of common autoimmune and inflammatory disorders. Intralesional injection has significantly reduced the rate of surgical intervention for benign inflammatory primary laryngeal pathology. Conclusions. Glucocorticoids are effective in the treatment of a number of laryngeal pathologies, through both systemic and intralesional administration. However, a clear consensus for utilization of glucocorticoids in treatment of specific laryngeal disorders has yet to be published.
    The Laryngoscope 07/2014; 124(7). DOI:10.1002/lary.24556 · 2.03 Impact Factor
  • Source
    Paul M Levine, Michael J Garabedian, Kent Kirshenbaum
    [Show abstract] [Hide abstract]
    ABSTRACT: The Androgen Receptor (AR) is a major therapeutic target in prostate cancer pharmacology. Progression of prostate cancer has been linked to elevated expression of AR in malignant tissue, suggesting that AR plays a central role in prostate cancer cell biology. Potent therapeutic agents can be precisely crafted to specifically target AR, potentially averting systemic toxicities associated with non-specific chemotherapies. In this review, we describe various strategies to generate steroid conjugates that can selectively engage AR with high potency. Analogies to recent developments in non-steroidal conjugates targeting AR are also evaluated. Particular focus is placed on potential applications in AR pharmacology. The review culminates with a description of future prospects for targeting AR.
    Journal of Medicinal Chemistry 06/2014; 57(20). DOI:10.1021/jm500101h · 5.48 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Although great advances have been made in the treatment of pediatric acute lymphoblastic leukemia, up to one out of five patients will relapse and their prognosis thereafter is dismal. We have previously identified recurrent deletions in TBL1XR1, which encodes for an F-box like protein responsible for regulating the nuclear hormone repressor (NCoR) complex stability. Here we model TBL1XR1 deletions in B-precursor ALL cell lines and show TBL1XR1 knockdown results in reduced glucocorticoid receptor recruitment to glucocorticoid responsive genes, and ultimately decreased glucocorticoid signaling caused by increased levels of NCoR1 and HDAC3. Reduction in glucocorticoid signaling in TBL1XR1 depleted lines resulted in resistance to glucocorticoid agonists, but not to other chemotherapeutic agents. Importantly, we show that treatment with the HDAC inhibitor SAHA restores sensitivity to prednisolone in TBL1XR1 depleted cells. Altogether, our data indicates that loss of TBL1XR1 is a novel driver of glucocorticoid-resistance in ALL and that epigenetic therapy may have future application in restoring drug sensitivity at relapse.
    Journal of Biological Chemistry 06/2014; 289(30). DOI:10.1074/jbc.M114.569889 · 4.60 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: While glucocorticoids (GCs) are used clinically to treat many conditions, their neonatal and prenatal usage is increasingly controversial due to reports of delayed adverse outcomes, especially affects on brain development. Such alterations may reflect the impact of GCs on neural progenitor/stem cell (NPSC) function. We previously demonstrated that the lipid raft protein Caveolin-1 (Cav-1) was required for rapid GC signaling in embryonic mouse NPSCs operating through plasma membrane-bound glucocorticoid receptors (GR). We show here that genomic GR signaling in NPSCs requires Cav-1. Loss of Cav-1 impacts the transcriptional response of many GR target genes (e.g. serum and glucocorticoid regulated kinase-1) that are likely to mediate the anti-proliferative effects of GCs. Microarray analysis of wild type C57 or Cav-1 deficient NPSCs identified approximately 100 genes that are differentially regulated by GC treatment. These changes in hormone responsiveness in Cav-1 knockout NPSCs are associated with the loss of GC-regulated phosphorylation of GR at serine 211, but not serine 226. Chromatin recruitment of total GR to regulatory regions of target genes such as Fkbp-5, RhoJ and Sgk-1 as well as p211-GR recruitment to Sgk-1 are compromised in Cav-1 KO NPSCs. Cav-1 is therefore a multi-functional regulator of GR in NPSCs influencing both rapid and genomic action of the receptor to impact cell proliferation.
    Molecular and Cellular Biology 04/2014; 34(14). DOI:10.1128/MCB.01121-13 · 5.04 Impact Factor
  • Molecular and Cellular Biology 09/2013; 33(20):4138-4138. DOI:10.1128/MCB.01139-13 · 5.04 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Androgen receptor (AR) is the major therapeutic target in aggressive prostate cancer. However, targeting AR alone can result in drug resistance and disease recurrence. Therefore, simultaneous targeting of multiple pathways could in principle be an effective approach to treating prostate cancer. Here we provide proof-of-concept that a small-molecule inhibitor of nuclear β-catenin activity (called C3) can inhibit both the AR and β-catenin-signaling pathways that are often misregulated in prostate cancer. Treatment with C3 ablated prostate cancer cell growth by disruption of both β-catenin/T-cell factor and β-catenin/AR protein interaction, reflecting the fact that T-cell factor and AR have overlapping binding sites on β-catenin. Given that AR interacts with, and is transcriptionally regulated by β-catenin, C3 treatment also resulted in decreased occupancy of β-catenin on the AR promoter and diminished AR and AR/β-catenin target gene expression. Interestingly, C3 treatment resulted in decreased AR binding to target genes accompanied by decreased recruitment of an AR and β-catenin cofactor, coactivator-associated arginine methyltransferase 1 (CARM1), providing insight into the unrecognized function of β-catenin in prostate cancer. Importantly, C3 inhibited tumor growth in an in vivo xenograft model and blocked renewal of bicalutamide-resistant sphere-forming cells, indicating the therapeutic potential of this approach.
    Proceedings of the National Academy of Sciences 09/2013; DOI:10.1073/pnas.1218168110 · 9.81 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Abnormal glucocorticoid and neurotrophin signaling have been implicated in numerous psychiatric disorders. However, the impact of neurotrophic signaling on glucocorticoid receptor (GR)-dependent gene expression is not understood. We therefore examined the impact of brain-derived neurotrophic factor (BDNF) signaling on GR transcriptional regulatory function by gene expression profiling in primary rat cortical neurons stimulated with the selective GR agonist dexamethasone (Dex) and BDNF, alone or in combination. Simultaneous treatment with BDNF and Dex elicited a unique set of GR-responsive genes associated with neuronal growth and differentiation and also enhanced the induction of a large number of Dex-sensitive genes. BDNF via its receptor TrkB enhanced the transcriptional activity of a synthetic GR reporter, suggesting a direct effect of BDNF signaling on GR function. Indeed, BDNF treatment induces the phosphorylation of GR at serine 155 (S155) and serine 287 (S287). Expression of a non-phosphorylatable mutant (GR S155A/S287A) impaired the induction of a subset of BDNF and Dex regulated genes. Mechanistically, BDNF-induced GR phosphorylation increased GR occupancy and cofactor recruitment at the promoter of a BDNF-enhanced gene. GR phosphorylation in vivo is sensitive to changes in the levels BDNF and TrkB as well as stress. Therefore, BDNF signaling specifies and amplifies the GR transcriptome through a coordinated GR phosphorylation-dependent detection mechanism.
    Molecular and Cellular Biology 07/2013; DOI:10.1128/MCB.00150-13 · 5.04 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: BACKGROUND: Androgen receptor (AR) expression in breast cancers may serve as a prognostic and predictive marker. We examined the expression pattern of AR and its phosphorylated forms, Ser-213 (AR-Ser[P]-213) and Ser-650 (AR-Ser[P]-650), in breast cancer and evaluated their association with clinicopathological parameters. METHODS: Immunohistochemistry was performed on primary and distant metastatic breast cancers and benign breast tissue using antibodies against AR, AR-Ser(P)-213, and AR-Ser(P)-650. The levels of cytoplasmic and nuclear expression were scored semiquantitatively using a histoscore. RESULTS: Nuclear staining of AR was observed in all benign breast tissue and 67% of cancer cases. Nuclear and cytoplasmic AR-Ser(P)-213 was increased in breast cancers 2-fold (P = .0014) and 1.7-fold (P = .05), respectively, compared with benign controls, whereas nuclear and cytoplasmic AR-Ser(P)-650 expression was decreased in tumors by 1.9-fold and 1.7-fold (both P < .0001), respectively. Increased expression of nuclear or cytoplasmic AR-Ser(P)-213 was observed in metastatic breast cancers (1.3-fold, P = .05), ER-negative (2.6-fold, P = .001), and invasive ductal carcinoma (6.8-fold, P = .04). AR-Ser(P)-650 expression was downregulated in lymph node-positive breast cancers (1.4-fold, P = .02) but was upregulated in invasive ductal carcinomas (3.2-fold, P < .0001) and metastases (1.5-fold, P = .003). Moreover, in ER-negative breast cancers, nuclear AR-Ser(P)-650 was decreased (1.4-fold, P = .005), and cytoplasmic AR-Ser(P)-650 was increased (1.4-fold, P = .003). CONCLUSIONS: AR and its phosphorylation at serines 213 and 650 are differentially expressed in breast cancer tumorigenesis and progression. Phosphorylation of AR at serines 213 and 650 is increased in ER-negative breast cancers, ductal carcinomas, and metastases and may have predictive value in breast cancer prognosis. Cancer 2013;000:000-000. © 2013 American Cancer Society.
    Cancer 07/2013; 119(14). DOI:10.1002/cncr.28092 · 4.90 Impact Factor
  • The Journal of Urology 04/2013; 189(4):e403. DOI:10.1016/j.juro.2013.02.563 · 3.75 Impact Factor
  • Eugine Lee, Michael Garabedian, Ramanuj DasGupta, Susan Logan
    The Journal of Urology 04/2013; 189(4):e328. DOI:10.1016/j.juro.2013.02.360 · 3.75 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The androgen receptor (AR) is a mediator of both androgen-dependent and castration-resistant prostate cancers. Identification of cellular factors affecting AR transcriptional activity could in principle yield new targets that reduce AR activity and combat prostate cancer, yet a comprehensive analysis of the genes required for AR-dependent transcriptional activity has not been determined. Using an unbiased genetic approach that takes advantage of the evolutionary conservation of AR signaling, we have conducted a genome-wide RNAi screen in Drosophila cells for genes required for AR transcriptional activity and applied the results to human prostate cancer cells. We identified 45 AR-regulators, which include known pathway components and genes with functions not previously linked to AR regulation, such as HIPK2 (a protein kinase) and MED19 (a subunit of the Mediator complex). Depletion of HIPK2 and MED19 in human prostate cancer cells decreased AR target gene expression and, importantly, reduced the proliferation of androgen-dependent and castration-resistant prostate cancer cells. We also systematically analyzed additional Mediator subunits and uncovered a small subset of Mediator subunits that interpret AR signaling and affect AR-dependent transcription and prostate cancer cell proliferation. Importantly, targeting of HIPK2 by an FDA-approved kinase inhibitor phenocopied the effect of depletion by RNAi and reduced the growth of AR-positive, but not AR-negative, treatment-resistant prostate cancer cells. Thus, our screen has yielded new AR regulators including drugable targets that reduce the proliferation of castration-resistant prostate cancer cells.
    Genome Research 02/2013; DOI:10.1101/gr.144774.112 · 13.85 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Endogenous estrogens that are synthesized in the body impact gene regulation by activating estrogen receptors in diverse cell types. Exogenous compounds that have estrogenic properties can also be found circulating in the blood in both children and adults. The genome-wide impact of these environmental estrogens on gene regulation is unclear. To obtain an integrated view of gene regulation in response to environmental and endogenous estrogens on a genome-wide scale, we performed ChIP-seq to identify estrogen receptor 1 (ESR1; previously estrogen receptor α) binding sites, and RNA-seq in endometrial cancer cells exposed to bisphenol A (BPA; found in plastics), genistein (GEN; found in soybean), or 17β-estradiol (E2; an endogenous estrogen). GEN and BPA treatment induces thousands of ESR1 binding sites and >50 gene expression changes, representing a subset of E2-induced gene regulation changes. Genes affected by E2 were highly enriched for ribosome-associated proteins; however, GEN and BPA failed to regulate most ribosome-associated proteins and instead enriched for transporters of carboxylic acids. Treatment-dependent changes in gene expression were associated with treatment-dependent ESR1 binding sites, with the exception that many genes up-regulated by E2 harbored a BPA-induced ESR1 binding site but failed to show any expression change after BPA treatment. GEN and BPA exhibited a similar relationship to E2 in the breast cancer line T-47D, where cell type specificity played a much larger role than treatment specificity. Overall, both environmental estrogens clearly regulate gene expression through ESR1 on a genome-wide scale, although with lower potency resulting in less ESR1 binding sites and less gene expression changes compared to the endogenous estrogen, E2.
    Genome Research 09/2012; DOI:10.1101/gr.135681.111 · 13.85 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Integration of cellular signaling pathways with androgen receptor (AR) signaling can be achieved through phosphorylation of AR by cellular kinases. However, the kinases responsible for phosphorylating the androgen receptor at numerous sites and the functional consequences of AR phosphorylation are only partially understood. Bioinformatic analysis revealed AR serine 213 (S213) as a putative substrate for PIM1, a kinase overexpressed in prostate cancer. Therefore, phosphorylation of AR serine 213 by PIM1 was examined using a phosphorylation site-specific antibody. Wild type PIM1, but not catalytically inactive PIM1, specifically phosphorylated AR but not an AR serine to alanine mutant (S213A). In vitro kinase assays confirmed that PIM1 can phosphorylate AR S213 in a ligand independent manner and cell type specific phosphorylation was observed in prostate cancer cell lines. Upon PIM1 overexpression AR phosphorylation was observed in the absence of hormone and was further increased in the presence of hormone in LNCaP, LNCaP-abl, and VCaP cells. Moreover, phosphorylation of AR was reduced in the presence of PIM kinase inhibitors. An examination of AR mediated transcription showed that reporter gene activity was reduced in the presence of PIM1 and wild type AR, but not S213A mutant AR. Androgen mediated transcription of endogenous PSA, Nkx3.1, and IGFBP5 was also decreased in the presence of PIM1 whereas IL6, cyclin A1, and caveolin 2 were increased. Immunohistochemical analysis of prostate cancer tissue microarrays showed significant P-AR S213 expression that was associated with hormone refractory prostate cancers, likely identifying cells with catalytically active PIM1. In addition, prostate cancers expressing a high level of P-AR S213 were twice as likely to be from biochemically recurrent cancers. Thus, AR phosphorylation by PIM1 at S213 impacts gene transcription and is highly prevalent in aggressive prostate cancer.
    Oncogene 09/2012; 32(34). DOI:10.1038/onc.2012.412 · 8.56 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Sustained treatment of prostate cancer with androgen receptor (AR) antagonists can evoke drug resistance, leading to castrate-resistant disease. Elevated activity of the AR is often associated with this highly aggressive disease state. Therefore, new therapeutic regimens that target and modulate AR activity could prove beneficial. We previously introduced a versatile chemical platform to generate competitive and non-competitive multivalent peptoid oligomer conjugates that modulate AR activity. In particular, we identified a linear and a cyclic divalent ethisterone conjugate that exhibit potent anti-proliferative properties in LNCaP-abl cells, a model of castrate-resistant prostate cancer. Here, we characterize the mechanism of action of these compounds utilizing confocal microscopy, time-resolved fluorescence resonance energy transfer, chromatin immunoprecipitation, flow cytometry, and microarray analysis. The linear conjugate competitively blocks AR action by inhibiting DNA binding. In addition, the linear conjugate does not promote AR nuclear localization or co-activator binding. In contrast, the cyclic conjugate promotes AR nuclear localization and induces cell-cycle arrest, despite its inability to compete against endogenous ligand for binding to AR in vitro. Genome-wide expression analysis reveals that gene transcripts are differentially affected by treatment with the linear or cyclic conjugate. Although the divalent ethisterone conjugates share extensive chemical similarities, we illustrate that they can antagonize the AR via distinct mechanisms of action, establishing new therapeutic strategies for potential applications in AR pharmacology.
    ACS Chemical Biology 08/2012; 7(10):1693-701. DOI:10.1021/cb300332w · 5.36 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The GR gene produces GRα and GRβ isoforms by alternative splicing of a C-terminal exon. GRα binds glucocorticoids, modulates transcription in a glucocorticoid dependent manner and has a growth inhibitory role in prostate cells. Due to this role glucocorticoids are often used to treat androgen independent prostate cancer. In contrast, GRβ has intrinsic transcriptional activity and binds mifepristone (RU486) but not glucocorticoids to control gene expression. To our knowledge the role of GRβ in prostate cell proliferation is unknown. We determined GRβ levels in various prostate cancer cell lines by reverse transcriptase-polymerase chain reaction and Western blot. The effect of GRβ on the kinetics of prostate cancer cell growth was determined by cell counting and flow cytometry upon mifepristone and dexamethasone treatment. Cell proliferation was also examined after siRNA mediated knockdown and over expression of GRβ. GRβ mRNA and protein were up-regulated in LNCaP cells that over expressed the androgen receptor co-factor ARA70β. Treatment of LNCaP-ARA70β with mifepristone or siRNA targeting GRβ inhibited proliferation compared to that of parental LNCaP cells. The immortal but nontumorigenic RC165 prostate cell line and the tumorigenic DU145 prostate cell line with endogenous GRβ also showed partial growth reduction upon GRβ depletion but to a lesser extent than LNCaP-ARA70β cells. The growth stimulatory effect of ARA70β on LNCaP cells was partly GRβ dependent, as was the proliferation of RC165 cells and to a lesser extent of DU145 cells. Results suggest that patients with a primary tumor that expresses GRβ and ARA70β may benefit from mifepristone.
    The Journal of urology 07/2012; 188(3):981-8. DOI:10.1016/j.juro.2012.04.102 · 3.75 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Glucocorticoids regulate gene expression by binding and activating the glucocorticoid receptor (GR). While ligand affinity determines the global sensitivity of the response, additional proteins act on the genome to tune sensitivity of some genes. However, the genomic extent and specificity of dose-specific glucocorticoid responses are unknown. We show that dose-specific glucocorticoid responses are extraordinarily specific at the genomic scale, able to distinctly express a single gene, the circadian rhythm gene for Period 1 (PER1), at concentrations consistent with the nighttime nadir of human cortisol. We mapped the PER1 response to a single GR binding site. The specific GR binding sequence did not impact sensitivity, and we instead attributed the response to a combination of additional transcription factors and chromatin accessibility acting in the same locus. The PER1 hypersensitive response element is conserved in the mouse, where we found similar upregulation of Per1 in pituitary cells. Targeted and transient overexpression of PER1 led to regulation of additional circadian rhythm genes hours later, suggesting that hypersensitive expression of PER1 impacts circadian gene expression. These findings show that hypersensitive GR binding occurs throughout the genome, drives targeted gene expression, and may be important to endocrine mediation of peripheral circadian rhythms.
    Molecular and Cellular Biology 07/2012; 32(18):3756-67. DOI:10.1128/MCB.00062-12 · 5.04 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: We have developed a mouse model of atherosclerotic plaque regression in which an atherosclerotic aortic arch from a hyperlipidemic donor is transplanted into a normolipidemic recipient, resulting in rapid elimination of cholesterol and monocyte-derived macrophage cells (CD68+) from transplanted vessel walls. To gain a comprehensive view of the differences in gene expression patterns in macrophages associated with regressing compared with progressing atherosclerotic plaque, we compared mRNA expression patterns in CD68+ macrophages extracted from plaque in aortic aches transplanted into normolipidemic or into hyperlipidemic recipients. In CD68+ cells from regressing plaque we observed that genes associated with the contractile apparatus responsible for cellular movement (e.g. actin and myosin) were up-regulated whereas genes related to cell adhesion (e.g. cadherins, vinculin) were down-regulated. In addition, CD68+ cells from regressing plaque were characterized by enhanced expression of genes associated with an anti-inflammatory M2 macrophage phenotype, including arginase I, CD163 and the C-lectin receptor. Our analysis suggests that in regressing plaque CD68+ cells preferentially express genes that reduce cellular adhesion, enhance cellular motility, and overall act to suppress inflammation.
    PLoS ONE 06/2012; 7(6):e39790. DOI:10.1371/journal.pone.0039790 · 3.53 Impact Factor
  • Paul M Levine, Keren Imberg, Michael J Garabedian, Kent Kirshenbaum
    [Show abstract] [Hide abstract]
    ABSTRACT: We introduce a family of multivalent peptidomimetic conjugates that modulate the activity of the androgen receptor (AR). Bioactive ethisterone ligands were conjugated to a set of sequence-specific peptoid oligomers. Certain multivalent peptoid conjugates enhance AR-mediated transcriptional activation. We identify a linear and a cyclic conjugate that exhibit potent anti-proliferative activity in LNCaP-abl cells, a model of therapy-resistant prostate cancer. The linear conjugate blocks AR action by competing for ligand binding. In contrast, the cyclic conjugate is active despite its inability to compete against endogenous ligand for binding to AR in vitro, suggesting a non-competitive mode of action. These results establish a versatile platform to design competitive and non-competitive AR modulators with potential therapeutic significance.
    Journal of the American Chemical Society 04/2012; 134(16):6912-5. DOI:10.1021/ja300170n · 11.44 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Glucocorticoid (GC) induction of the tyrosine aminotransferase (TAT) gene by the glucocorticoid receptor (GR) is a classic model used to investigate steroid-regulated gene expression. Classic studies analyzing GC-induction of the TAT gene demonstrated that despite having very high affinity for GR, some steroids cannot induce maximal TAT enzyme activity, but the molecular basis for this phenomenon is unknown. Here, we used RT-PCR and chromatin immunoprecipitation to determine TAT mRNA accumulation and GR recruitment to the TAT promoter (TAT-GRE) in rat hepatoma cells induced by seven GR ligands: dexamethasone (DEX), cortisol (CRT), corticosterone (CCS), 11-deoxycorticosterone (DOC), aldosterone (ALD), progesterone (PRG) and 17-hydroxyprogesterone (17P). As expected, DEX, CRT, CCS and ALD all induced both TAT mRNA and GR recruitment to the TAT-GRE, while PRG and 17P did not. However, while DOC could not induce significant TAT mRNA, it did induce robust GR occupancy of the TAT-GRE. DOC also induced recruitment of the histone acetyltransferase p300 to the TAT-GRE as efficiently as DEX. These DOC-induced effects recapitulated at another GR target gene (sulfonyltransferase 1A1), and DOC also failed to promote the multiple changes in gene expression required for glucocorticoid-dependent 3T3-L1 adipocyte differentiation. Structural simulations and protease sensitivity assays suggest that DOC and DEX induce different conformations in GR. Thus, although steroids that bind GR with high affinity can induce GR and p300 occupancy of target promoters, they may not induce a conformation of GR capable of activating transcription.
    Biochemical and Biophysical Research Communications 03/2012; 420(4):839-44. DOI:10.1016/j.bbrc.2012.03.084 · 2.28 Impact Factor

Publication Stats

5k Citations
613.82 Total Impact Points

Institutions

  • 1998–2014
    • NYU Langone Medical Center
      • Department of Microbiology
      New York, New York, United States
  • 1997–2013
    • CUNY Graduate Center
      New York, New York, United States
  • 2012
    • Duke University
      Durham, North Carolina, United States
  • 2010
    • VU University Amsterdam
      Amsterdamo, North Holland, Netherlands
  • 2006
    • Hospital for Special Surgery
      New York City, New York, United States
  • 2003
    • Cornell University
      Итак, New York, United States
  • 2002
    • Comprehensive Cancer Centers of Nevada
      Las Vegas, Nevada, United States
  • 1992–1999
    • University of California, San Francisco
      • Department of Biochemistry and Biophysics
      San Francisco, California, United States