Dissertations / Theses on the topic 'Receptors, Cytoplasmic and Nuclear – genetics'

In mammals, circadian rhythms are generated by transcriptional-translational feedback loops consisting of a set of clock genes and their protein products. Among them, Bmal1 is a critical clock gene in generating and maintaining circadian rhythms. Moreover, orphan nuclear receptors REV-ERBs and RORs were known to respectively repress and activate Bmal1 transcription. In our study, we further demonstrated that: (1) REV-ERBalpha might be the main regulator in maintaining Bmal1 oscillation in thymus. (2) Rorgamma mRNA is constant in muscle and testis, and rhythmic in liver, while Rorgammat mRNA is only expressed in thymus, at constant levels. Moreover, the expressions of these two Rorgamma isoforms are affected in Clock mutant mice in a distinct way. (3) RORgamma and RORgammat can activate Bmal1 transcription at a similar level. (4) Rorgamma is a clock-controlled gene. Altogether, our results suggest that the crucial role of REV-ERBs and RORs in peripheral clocks. Furthermore, our work highlights functional differences among mammalian peripheral clocks, which provides important insights into the complexity of the circadian system.

Nuclear hormone receptors (NHR) constitute a superfamily of ligand inducible transcriptional activators that enable an organism to regulate development and homeostasis through switching on or off target genes in response to stimuli reflecting changes in environment as well as endocrine. NHRs include classical steroid hormone receptors (GR, AR, ER and MR) and retinoid, thyroid hormone receptors. One long-term goal of our lab is to understand the molecular mechanisms through which the transcriptional activity of NHRs is regulated. Extensive studies in the past few years have revealed that in addition to the dependence on ligand availability, the transcriptional activity of NHRs is also regulated by two types of proteins: co activators and corepressors. In the absence of ligand, many NHRs, including TR and RAR can actively repress target gene transcription with the help of corepressors, proteins that physically interact with both NHRs and histone deacetylases (HDACs). Functional interactions between NHRs and corepressors therefore lead to tightly compact and transcriptionally non-permissive chromatin structures after the removal of obstructive acetyl groups from histone tails by HDACs. On the other hand, ligand binding stabilizes NHRs in a conformation that favors interaction with proteins other than corepressors; many of these proteins are able to potentiate the transcriptional activity of NHRs through various mechanisms, such as histone acetylation, chromatin remodeling and recruitment of basal transcription machinery and are collectively termed coactivators. Two highly related corepressors, SMRT (silencing mediator of retinoid and thyroid hormone receptors) and N-CoR (nuclear receptor corepressor), have been cloned. This research in corepressor SMRT started by a systematic study of its subcellular localization. We found that SMRT predominantly forms a specific nuclear punctuate structure that does not appear to overlap with any other well-known subnuclear domains/speckles. Although our searching for specific sequence signals that may determine the specific speckle localization of SMRT did not yield conclusive results, we discovered the colocalization of unliganded RAR and certain HDACs, including HDAC1, 3,4 and 5, in the SMRT nuclear speckles. Moreover, SMRT is likely to be the organizer of such speckles since it appears to be able to recruit other proteins into these speckles. The presence of HDAC1 in the SMRT speckles suggests a direct association between these two proteins, which has not been detected by previous biochemical analyses. Interestingly, HDAC1 point mutants that are completely defective in deacetylase activity failed to locate to SMRT nuclear speckles, while another partially active mutant maintained the colocalization. These discoveries may indicate SMRT nuclear speckles as novel nuclear domains involved in transcriptional repression. More physiologically relevant support for this hypothesis arises from study of HDAC4 and 5. HDAC4 and 5 are potent inhibitors of transcriptional activator MEF2C. Nuclear presence of HDAC4/5 can block the activation of MEF2C, which is required during muscle differentiation. Normally, HDAC4 is predominantly located in cytoplasm. However, we found that in the presence of SMRT overexpression, HDAC4 was found mostly in SMRT nuclear speckles. This accumulation enhanced HDAC4 mediated inhibition on MEF2C transcriptional activity in a transient transfection assay. SMRT overexpression also resulted in accumulation of HDAC5 in the SMRT nuclear speckles compared to the nuclear diffuse distribution in the absence of SMRT. Again, this accumulation of HDAC5 in nuclear speckles correlated with enhanced inhibition of MEF2C. Taken together, our study suggested that instead of being merely a corepressor for NHRs, SMRT might function as an organizer of a nuclear repression domain, which may be involved in a broad array of cellular processes. In contrast to the limited number of corepressors, numerous co activators have been identified; the SRC (or p160) family is relatively well studied. This family includes three highly related members, SRC-1, TIF2/GRIP1, RAC3/AIB1/ACTR/p/CIP. Similar domain structures are shared among these factors, with the most highly conserved region, the bHLH-PAS domain found within the N terminal ~400 amino acid residues. This study of RAC3 aims to identify the function of the highly conserved N terminal bHLH-PAS domain by isolating interacting proteins through yeast two-hybrid screening. One candidate gene isolated encodes the C terminal fragment of the human homologue of the yeast protein MMS19. Functional studies of this small fragment revealed that it specifically interacted with human estrogen receptors (ERs) and inhibited ligand induced transcriptional activity of ERs in the transient transfection assay. Then we cloned the full-length human MMS19 cDNA and characterized the hMMS19 as a weak coactivator for estrogen receptors in the transient transfection assay. Furthermore, when tested on separate AF-1 or AF-2 of ERs, hMMS19 specifically enhanced AF-1 but had no effect on AF-2. These results identified hMMS19 as a specific coactivator for ER AF-1.

The steroid/thyroid hormone receptor superfamily is a large class of ligand-dependent transcription factors that plays a critical role in regulating the expression of genes involved in a broad range of physiological functions, including development, homeostasis, and reproduction. In the absence of cognate hormone, several receptors are able to repress transcription below the basal level via the recruitment of the nuclear receptor corepressors SMRT and NCoR. Upon hormone binding by the receptor, the corepressor complex is dissociated and a coactivator complex is subsequently recruited. This thesis details the mechanisms by which receptor-associated coactivator 3 (RAC3) interacts with nuclear receptors, particularly the vitamin D, estrogen, and retinoid receptors, and modulates their transcriptional activity. It was discovered that these receptors interact with different α-helical LXXLL motifs of RAC3 in vitro. Mutation of specific motifs differentially impairs the ability of RAC3 to enhance transcription by the receptors in vivo. In addition, the intrinsic transcriptional activation function of RAC3 was also characterized. Here, a single LXXLL motif, NR box v, was found to be essential to activation by serving as a binding surface for the general transcriptional integrator CBP/p300. Finally, the cofactor binding pocket of retinoid receptors was characterized. It was demonstrated that, to a large extent, the coactivator pocket of RARα overlaps with the corepressor pocket, with the exception of helix 12, which is required for coactivator, but not corepressor binding. Recruitment of RAC3 or SMRT also correlates directly with the ability of RARα to activate or repress transcription, respectively. Intriguingly, it was discovered that the AF-2 domain of RXRα inhibited cofactor binding to RXRα heterodimers, for deletion of this domain dramatically enhanced RAC3 and SMRT binding. In addition, it was demonstrated that the RXRα cofactor binding pocket contributed minimally to recruitment of cofactors. Conversely, the AF-2 domain of the partnering monomer and its cofactor pocket were required for these interactions. These findings suggest that the partner of RXRα is the primary docking point for cofactors at RXRα heterodimeric complexes. Taken together, this work contributes significantly to the field of nuclear receptor function in detailing the mechanisms by which the coactivator RAC3 is recruited to nuclear receptors and regulates their transcriptional activity.

In multicellular organisms, determining when and where genes will be expressed is critical for their development and physiology. Transcription factors (TFs) are major specifiers of differential gene expression. By establishing physical contacts with the regulatory elements of their target genes, TFs often determine whether the target genes will be expressed or not. These physical and/or regulatory TF-DNA interactions can be modeled into gene regulatory networks (GRNs), which provide a systems-level view of differential gene expression. Thus far, much of the GRN delineation efforts focused on metazoan development, whereas the organization of GRNs that pertain to systems physiology remains mostly unexplored. My work has focused on delineating the first gene regulatory network of the nematode Caenorhabditis elegans metabolic genes, and investigating how this network relates to the energy homeostasis of the nematode. The resulting metabolic GRN consists of ~70 metabolic genes, 100 TFs and more than 500 protein–DNA interactions. It also includes novel protein-protein interactions involving the metabolic transcriptional cofactor MDT-15 and several TFs that occur in the metabolic GRN. On a global level, we found that the metabolic GRN is enriched for nuclear hormone receptors (NHRs). NHRs form a special class of TFs that can interact with diffusible biomolecules and are well-known regulators of lipid metabolism in other organisms, including humans. Interestingly, NHRs comprise the largest family of TFs in nematodes; the C. elegans genome encodes 284 NHRs, most of which are uncharacterized. In our study, we show that the C. elegans NHRs that we retrieved in the metabolic GRN organize into network modules, and that most of these NHRs function to maintain lipid homeostasis in the nematode. Network modularity has been proposed to facilitate rapid and robust changes in gene expression. Our results suggest that the C. elegans metabolic GRN may have evolved by combining NHR family expansion with the specific modular wiring of NHRs to enable the rapid adaptation of the animal to different environmental cues.

Nuclear hormone receptors (NHRs) are ligand-activated transcriptions factors which transduce the effects of various hormones as well as nutritional and other environmental signals. They thus function to maintain physiological homeostasis by integrating the tissue expression of specific target genes to regulate a wealth of biological processes including reproduction, development, metabolism and environmental adaptation. Mounting evidence indicates NHRs are the target of endocrine disrupting compounds (EDCs), exogenous chemicals, often of anthropogenic origin, which disrupt NHRs and thus the processes under their control. EDCs can interfere with NHR signalling by activating receptors (agonists), by inhibiting the actions of the receptor (antagonists), or by disrupting endogenous hormone synthesis, secretion, transport or metabolism. Much of the focus to date has been on the risk of EDCs to reproductive functions, via estrogen and androgen NHRs in humans, and also in aquatic organisms. However environmental pollutants also have the potential to interact with other NHRs, particularly in aquatic environments, and cause dysregulation of other critical physiological processes, including energy homeostasis, immune functions and the stress response. To address this possibility a reporter gene assay was developed, allowing the high-throughput screening of pollutants for their interactions with piscine NHRs with critical roles in energy homeostasis, stress reponse and immune functions, namely the peroxisome proliferator-activated receptors (PPARs) and corticosteroid receptors (CRs) from European plaice (Pleuronectes platessa) and European flounder (Platichthys flesus), respectively. Complementary DNA (cDNA) sequences encoding the ligand-binding domains of PPARs and CRs, critical for receptor-ligand interactions and receptor activation, were ligated to the DNA-binding domain (DBD) of the yeast Gal4 transcription activator protein to create experimental expression plasmid constructs. Co-transfection of these expression plasmids into the fathead minnow (FHM) cell line with an upstream-activating sequence (UAS)-firefly luciferase reporter gene plasmid increased luciferase expression in the presence of known PPAR and CR ligands. Several aquatic pollutants including pharmaceuticals, industrial by-products and biocides were tested for their potential to disrupt PPAR and CR functions by interacting with these receptors in an agonistic or antagonistic manner. Several fibrates, a group of pharmaceutical compounds used to treat dyslipidemia in humans by targeting the PPARs, were able to activate plaice Gal4-PPARα and Gal4-PPARβ in the reporter gene assay, indicative of an interaction with PPAR receptors in non-target species. Fibrates which did not activate Gal4-PPARα were able to inhibit the activation of Gal4-PPARα by the PPARα-specific agonist, Wy14643, suggesting differential effects of fibrates on human and flounder PPARs. In addition some metabolites of widespread phthalate ester pollutants were also agonists of the Gal4-PPARα and Gal4-PPARβ constructs. The Gal4-PPARγ construct was unresponsive to almost all the compounds tested, including the mammalian PPARγ agonist, rosiglitazone. The exception to this was the phthalate metabolite monobenzylphthalate, which induced a small increase in firefly luciferase in Gal4-PPARγ transfected cells. All of the above effects required concentrations of at least 10 µM, which are unlikely to be encountered in the aquatic environment. In contrast bis(tributyltin) oxide (TBTO), a notorious environmental pollutant, inhibited Gal4-PPARα and Gal4-CR constructs at concentrations as low as 1 nM and 100 nM, respectively. These concentrations are lower than those reported in aquatic environments, or in fish tissues, making TBTO a candidate endocrine disruptor in fish by inhibiting PPARα and CR signalling. A European flounder cDNA microarray was used to investigate the trasnscriptional responses of flounder hepatocytes to TBTO (10 nM) exposure. Exposure to TBTO and Wy14643, both alone and in combination, indicated a TBTO-driven downregulation of several potential PPARα-target genes with functions in the immune system, the proteasome, and lipid metabolism, although, based on mammalian comparisons, some potential PPARα-target genes were also upregulated, indicating differences in mammalian and fish PPAR-target genes or reflecting the complexity of organisms at a higher organisational level than cell-based assay systems. However, the microarray-based approach was useful in formulating further hypotheses about the effects of TBTO on PPARα signalling. Overall, these results indicate that exogenous chemicals entering the aquatic environment can interfere with NHRs with functions in energy homeostasis, immune functions and stress, in non-target organisms. The cell-based reporter gene assay is a useful tool for identifying potential endocrine disruptors which target PPARs and CRs and would be a useful method in a first tier testing approach, limiting the use of live animal models and enabling investigation into specific receptors which are targets of endocrine disrupting compounds. Although more work is required to confirm the physiological consequences of TBTO inhibition of PPARα, the results presented here indicate that organisms inhabiting TBTO-polluted environments may experience suppression of the immune system, an increase in non-functional or misfolded proteins through suppression of genes involved in the ubiquitin/proteasome system and a disruption in lipid homeostasis.

Thesis (MSc)--Stellenbosch University, 2014.
ENGLISH ABSTRACT: Efavirenz is an antiretroviral drug used in the treatment of HIV-positive patients as part of first line triple-highly active antiretroviral therapy. Treatment response varies among individuals and adverse drug reactions tend to occur, as a result of the variation in the rate of efavirenz metabolism among individuals. This is partly caused by genetic variation; therefore the study of genes involved in the metabolism of efavirenz, such as CYP2B6, could potentially enhance treatment success. The effect of CYP2B6 SNP 516G>T (part of the CYP2B6*6 allele) is particularly important, as individuals homozygous for the minor allele of this SNP have significantly increased efavirenz levels. Furthermore, nuclear receptors, specifically constitutive androstane receptor, encoded by NR1I3, and pregnane X receptor, encoded by NR1I2, are involved in the regulation of the genes responsible for efavirenz metabolism and could therefore indirectly influence the pharmacokinetics of efavirenz. The current study identified variants in the NR1I3 and NR1I2 genes through in silico analysis, bi-directional sequencing and literature searches. A total of nine NR1I3 and ten NR1I2 target variants were subsequently genotyped in 132 HIV-positive female patients from the Xhosa and Cape Mixed Ancestry populations. The resulting genotype and allele frequencies were statistically analysed to search for correlations between genetic variations and available efavirenz levels in hair samples, treatment outcome as measured by viral load, and the occurrence of adverse drug reactions. The minor allele of a NR1I2 5’-upstream SNP, rs1523128 (6334A>G), was significantly associated with decreased efavirenz levels. From analysis of the effect of composite SNPs, NR1I3 5’-upstream SNP rs55802895 (258G>A) in conjunction with CYP2B6*6, was significantly associated with efavirenz-levels. It was found that the minor allele of rs55802895 inhibited the effect of CYP2B6*6, resulting in normal efavirenz levels for individuals homozygous for the minor allele of both SNPs. Additionally, when the target NR1I3 and NR1I2 variants were analysed in conjunction with six SNPs from CYP1A2, CYP2A6, CYP3A4 and CYP3A5, 11 compound genotypes were shown to be statistically associated with mean EFV plasma levels. The study emphasises the complexity of efavirenz metabolism, and the importance of transcriptional regulation in xenobiotic metabolism.
AFRIKAANSE OPSOMMING: Efavirenz is ‘n antiretrovirale middel wat gebruik word in die behandeling van HIV-positiewe pasiënte as deel van drievoudige hoogs-aktiewe antiretrovirale terapie. Reaksie op behandeling verskil tussen individue en nadelige newe-effekte, wat veroorsaak word deur die verskil in tempo waarteen efavirenz gemetaboliseer word, neig om voor te kom. Hierdie verskille word gedeeltelik veroorsaak deur genetiese variasie; dus kan die studie van gene betrokke by die metabolisme van efavirenz, soos CYP2B6, moontlik die sukses van behandeling verhoog. Die effek van CYP2B6 SNP 516G>T (deel van die CYP2B6*6-alleel) is veral belangrik, want individue wat homosigoties is vir die minderheids-alleel het betekenisvol hoë efavirenz-vlakke. Nukleêre reseptore, spesifiek konstitutiewe androstane reseptor, deur NR1I3 gekodeer, en pregnane X reseptor, deur NR1I2 gekodeer, is betrokke by die regulering van die gene verantwoordelik vir efavirenz-metabolisme en kan dus die farmakokinetika van efavirenz beïnvloed. Die huidige studie het variante in NR1I3 en NR1I2 identifiseer deur in silico-analise, bi-direksionele volgordebepaling en ’n literatuurstudie. Nege NR1I3 en tien NR1I2-variante in totaal is vervolglik gegenotipeer in 132 HIV-positiewe vroulike pasiënte van Xhosa en Kaapse Gemengde Afkoms populasies. Die gevolglike genotipe- en alleelfrekwensies is statisties geanaliseer om vir korrelasies tussen genetiese variasies en beskikbare efavirenz-vlakke in haarmonsters, uitkoms van behandeling gemeet in virale lading en die voorkoms van nadelige newe-effekte te soek. Daar is gevind dat die minderheids-alleel van ’n NR1I2 5’-stroomop SNP, rs1523128 (6334A>G), betekenisvol geassosieer is met ’n daling in efavirenz-vlakke. Vanuit die saamgestelde SNPs, is die NR1I3 5’-stroomop SNP rs55802895 (258G>A), tesame met CYP2B6*6, betekenisvol geassosieer met efavirenz-vlakke. Daar is gevind dat die minderheids-alleel van rs55802895 die effek van CYP2B6*6 demp, en gevolglik normale efavirenz-vlakke in individue homosigoties vir die minderheids-allele van albei SNPs veroorsaak. Addisioneel is die teiken NR1I3 en NR1I2 variante gemeenskaplik met ses SNPs van CYP1A2, CYP2A6, CYP3A4 en CYP3A5 geanaliseer en 11 gekombineerde genotipes is statisties geassosieer met gemiddelde EFV plasma vlakke. Hierdie studie beklemtoon die kompleksiteit van efavirenz-metabolisme en die belangrikheid van transkripsionele regulering in xenobiotiese metabolisme.
National Research Foundation (NRF)

Thesis (Ph.D)--Chemistry and Biochemistry, Georgia Institute of Technology, 2009.
Committee Chair: Doyle, Donald; Committee Member: Barry, Bridgette; Committee Member: Bommarius, Andreas; Committee Member: Ledoux, Joe; Committee Member: Matsumura, Ichiro; Committee Member: Oyelere, Adegboyega. Part of the SMARTech Electronic Thesis and Dissertation Collection.

mRNA degradation is a fundamental process that controls both the level and the fidelity of gene expression. Using a combination of bioinformatic, genomic, genetic, and molecular biology approaches, we have shown that Edc3p, a yeast mRNA decay factor, controls the stability of the intron-containing YRA1 pre-mRNA. We found that Edc3p-mediated degradation of YRA1 pre-mRNA: 1) is a component of a negative feedback loop involved in the autoregulation of YRA1, 2) takes place in the cytoplasm, 3) is independent of translation, 4) occurs through a deadenylation-independent decapping and 5΄ to 3΄ exonucleotic decay mechanism, and 5) is controlled by specific cis-acting elements and trans-regulatory factors. Cis-regulation of YRA1 pre-mRNA degradation is complicated and precise. Sequences in exon1 inhibit YRA1 pre-mRNA splicing and/or promote pre-mRNA export in a size-dependent but sequence-independent manner. Sequences in the intron dictate the substrate specificity for Edc3p-mediated decay. Five structurally different but functionally interdependent modules were identified in the YRA1 intron. Two modules, designated Edc3p-responsive elements (EREs), are required for triggering an Edc3p-response. Three other modules, designated translational repression elements (TREs), are required for repressing translation of YRA1 pre-mRNA. TREs enhance the efficiency of the response of the EREs to Edc3p by inhibiting translation-dependent nonsense-mediated mRNA decay (NMD). Trans-regulation of YRA1 pre-mRNA is governed by Yra1p, which inhibits YRA1 pre-mRNA splicing and commits the pre-mRNA to nuclear export, and the RNP export factors, Mex67p and Crm1p, which jointly promote YRA1 pre-mRNA export. Mex67p also appears to interact with sequences in the YRA1 intron to promote translational repression and to enhance the Edc3p response of YRA1 pre-mRNA. These results illustrate how common steps in the nuclear processing, export, and degradation of a transcript can be uniquely combined to control the expression of a specific gene and suggest that Edc3p-mediated decay may have additional regulatory functions in eukaryotic cells.

Nuclear receptors are ligand-activated transcription factors that play significant roles in various biological processes within the body, such as cell development, hormone metabolism, reproduction, and cardiac function. As transcription factors, nuclear receptors are involved in many diseases, such as diabetes, cancer, and arthritis, resulting in approximately 10-15% of the pharmaceutical drugs presently on the market being targeted toward nuclear receptors. Structurally, nuclear receptors consist of a DNA-binding domain (DBD), responsible for binding specific sequences of DNA called response elements, fused to a ligand-binding domain (LBD) through a hinge region. The LBD binds a small molecule ligand. Upon ligand binding, the LBD changes to an active conformation leading to the recruitment of coactivator (CoAC) proteins and initiation of transcription. As a result of their involvement in disease, there is an emphasis on engineering nuclear receptors for applications in gene therapy, drug discovery and metabolic engineering.

Pleckstrin homology (PH) domains, which play an essential role in membrane trafficking and signal transduction, recognize phosphoinositides with a diverse range of affinities and specificities. The PH domains of the Grp1 family of Arf GTPase exchange factors recognize a select group of phosphoinositides with dramatic differences in specificity, despite 90% sequence identity. The work described in this thesis has focused on the structural basis for these differences. The structure of the Grp1 PH domain revealed structural determinants for phosphoinositide recognition. Through a wide range of crystallographic and biochemical means, the structural basis that accounts for the differential binding affinities amongst the Grp1 family PH domains has also been determined. Furthermore, examination of the structural details of these PH domains bound to different inositol phosphate groups have aided in understanding the structural mechanisms by which all PH domains recognize phosphoinositides.

Cells must regulate their metabolism in order to grow, adapt to changes in nutrient availability and maintain homeostasis. Flux, or the turnover of metabolites, through the metabolic network can be regulated at the allosteric and transcriptional levels. While study of allosteric regulation is limited to biochemical examination of individual proteins, transcriptional control of metabolism can be explored at a systems level. We endeavored to elucidate transcriptional mechanisms of metabolic flux regulation in the model organism Caenorhabditis elegans (C. elegans). We also worked to create a visual tool to explore metabolic pathways that will support future efforts in the research of metabolic gene regulation. C. elegans is a small, free-living nematode that feeds on bacteria and experiences a high level of diversity in nutrient level and composition. Previously, we identified a mechanism by which the essential cofactor, vitamin B12, regulates the expression of genes involved in the degradation of propionate, referred to as B12‑mechanism‑I. This mechanism functions to prevent the toxic accumulation of propionate and requires the TFs NHR-10 and NHR-68. Using genetic screens as well as transcriptomic and metabolomic approaches, we discover a second mechanism by which vitamin B12 regulates metabolic gene expression: B12-mechanism-II. Unlike B12-mechanism-I, B12-mechanism-II is independent of propionate, requires the transcription factor NHR-114 and functions to maintain the metabolic activity of the Methionine/S-adenosylmethionine cycle in a tightly regulated regime. We also present WormPaths, an online resource that allows visualization of C. elegans metabolic pathways and enables metabolic pathway enrichment of user-uploaded transcriptomic data.

The work in this thesis addresses the general problem of how ribosomal subunits are exported from the nucleus to mature in the cytoplasm. There are three parts in this dissertation. In the first part, I asked questions about the specificity for export receptors in the nuclear export of the large (60S) ribosomal subunit in yeast. In principle, I tethered different export receptors that are known to work in various unrelated export pathways to the ribosome by fusing them to the trans-acting factor Nmd3. Interestingly, all the chimeric receptors were able to support export, although to different degrees. Moreover, 60S export driven by these chimeric receptors was independent of Crm1, an export receptor that is essential for 60S export in wild-type cells. The second question I addressed in this project was whether or not a nuclear export signal could be provided in cis on ribosomal proteins (Rpls) rather than in trans by a transacting factor. The nuclear export signal (NES) of Nmd3 was fused to different ribosomal proteins and tested for support of 60S export. Several Rpl-NES fusion constructs worked to promote 60S export. Rpl3 gave the best efficiency. In conclusion, these results imply unexpected flexibility in the 60S export pathway. This may help explain how different export receptors could have evolved in different eukaryotic lineages. In the second part of my thesis, I identified the assembly pathway for the base of the ribosome stalk. The stalk is an important functional domain of the large ribosomal subunit because of its requirement for interaction with translation factors. Mrt4 is a nuclear paralog of P0, which is an essential part of the stalk. Here, I identified Yvh1 a novel ribosome biogenesis factor that is required for the release of Mrt4. Yvh1 is a conserved dual phosphatase, but the C-terminal zinc-binding domain rather than the phosphatase function was required for its activity to release Mrt4. Mrt4 localizes in the nucleus and nucleolus in the wild-type cells, but was persistent on cytoplasmic 60S subunits in yvh1[Delta] cells. The persistence of Mrt4 on the 60S subunits blocked the loading of P0 and assembly of the stalk. I also found the binding of Yvh1 depended on Rpl12, a protein that binds together with P0 to form the base of the stalk. Deletion of Rpl12 phenocopied yvh1[Delta]. These data identified the function of Yvh1 as a release factor of Mrt4. I also showed that the function of Yvh1 is conserved in human cells. In my final project, I analyzed the interdependence and order of the known cytoplasmic maturation events of the 60S subunit. 60S subunits require several maturation steps in the cytoplasm before they become competent in translation. There are four major steps involving two ATPases, Drg1 and Ssa1, and two GTPases, Efl1 and Lsg1. In my study, I ordered these steps into one serial pathway. Drg1 releases Rlp24 in the earliest step of 60S maturation in the cytoplasm. Truncation of the C-terminus of Rlp24 blocked cytoplasmic maturation of the large subunit by preventing the recruitment of Drg1 and led to a secondary defect in the release of Arx1 because of a failure to recruit Rei1. Deletion of REI1 mislocalized Tif6 from the nucleus and nucleolus to the cytoplasm and deletion of ARX1 suppressed the Tif6 mislocalization, indicating that the release of Arx1 was required for Tif6 release downstream. I found that mutation of efl1 or sdo1, the known release factors for Tif6, also blocked Nmd3 release. Tif6-V192F, which could bypass the growth defects of efl1 or sdo1 mutants, suppressed the defect of Nmd3 recycling. These results showed that the release of Tif6 was a prerequisite for Nmd3 release. Thus, the release of Nmd3 is downstream of the Tif6 release step. In conclusion, I have ordered the events of cytoplasmic maturation with Drg1 as the first step after ribosome export, followed by Rei1/Jji1 and then Sdo1/Efl1. The release of Nmd3 by Lsg1 appears to be the last step of ribosome maturation in the cytoplasm. Thus, the two ATPases Drg1 and Ssa work first and then the two GTPases Efl1 and Lsg1 work in a linear pathway of 60S maturation in the cytoplasm.
text

Cheng, Cho Yiu.
Thesis (M.Phil.)--Chinese University of Hong Kong, 2011.
Includes bibliographical references (leaves 186-217).
Abstracts in English and Chinese.
Acknowledgements --- p.1
Abstract of thesis --- p.2
Abstract of thesis in Chinese --- p.7
Presentation attended --- p.9
Chapter Chapter 1: --- Introduction and Background --- p.13
Chapter 1.1 --- Anatomy and functions of human prostate gland --- p.13
Chapter 1.2 --- Worldwide epidemiology of prostate cancer --- p.15
Chapter 1.3 --- Prostate cancer stages and treatments in clinic --- p.21
Chapter 1.4 --- Introduction to nuclear receptors --- p.23
Chapter 1.5 --- Nuclear receptor structure --- p.24
Chapter 1.6 --- Nuclear receptors nomenclature and classification --- p.28
Chapter 1.7 --- Mode of action for nuclear receptors --- p.34
Chapter 1.8 --- Co-regulators of nuclear receptors --- p.35
Chapter 1.9 --- Nuclear receptors related to prostate cancer --- p.43
Chapter Chapter 2: --- Aim of study and experimental design --- p.59
Chapter 2.1 --- Aim of study --- p.59
Chapter 2.2 --- In vitro cell lines models used in the study --- p.60
Chapter Chapter 3: --- Materials and methods --- p.64
Chapter 3.1 --- Apparatus and preparation throughout the study --- p.64
Chapter 3.2 --- Cells culture --- p.64
Chapter 3.3 --- RNA extraction --- p.67
Chapter 3.4 --- Reverse transcription --- p.68
Chapter 3.5 --- Primers specificity checking --- p.69
Chapter 3.6 --- Real time quantitative polymerase chain reaction --- p.84
Chapter 3.7 --- Data analysis --- p.90
Chapter Chapter 4: --- Results --- p.92
Chapter 4.1 --- Expression of nuclear receptors transcripts in each prostatic cell lines used --- p.92
Chapter 4.2 --- Expression of nuclear receptor transcripts in immortalized prostatic epithelial BPH-1 and BPH-1 derived cell lines model --- p.116
Chapter 4.3 --- Expression of nuclear receptor transcripts in androgen-dependent and androgen-independent classical prostatic cancer cell lines model --- p.121
Chapter 4.4 --- Expression of nuclear receptor transcripts in androgen-independent and antiandrogen-resistant LNCaP derived cell lines model --- p.125
Chapter Chapter 5: --- Discussion --- p.129
Chapter 5.1 --- Special expression pattern of some nuclear receptors in the prostatic cell lines or prostatic cancer cell lines --- p.129
Chapter 5.2 --- BPH-1 and BPH-1 derived cell lines model --- p.138
Chapter 5.2.1 --- Prostatic cell lines model studying the transformation and invasion in prostate cancer (BPH-1 Snail & BPH-1 CAFTDs versus BPH-1) --- p.138
Chapter 5.2.2 --- Prostatic cell lines model studying the transformation and invasion in prostate cancer (BPH-1 Snail & BPH-1 CAFTDs versus BPH-1 AR) --- p.159
Chapter 5.3.3 --- classical prostatic cancer cell lines model --- p.162
Chapter 5.3.1 --- Prostatic cancer cell lines model studying androgen-dependence and androgen-independence (DU145 & PC-3 versus LNCaP) --- p.163
Chapter 5.4 --- LNCaP and LNCaP derived cell lines model --- p.170
Chapter 5.4.1 --- Prostatic cancer cell lines model studying androgen-independence and antiandrogen-resistance (LNCaP-abl & LNCaP-BCs versus LNCaP) --- p.171
Chapter Chapter 6: --- Conclusion --- p.179
References --- p.186

Nuclear receptors (NR’s) comprise a large, ancient, superfamily of eukaryotic transcription factors that govern a wide range of metabolic, homeostatic, and developmental pathways, and which have been implicated in disease states including cancer, inflammation, and diabetes. The ability of NRs to activate or repress gene transcription is modulated through direct binding of small lipophilic ligands which induce conformational changes in their cognate receptor. These changes are structural in nature and lead to the recruitment of coactivator or corepressor complexes, ultimately regulating the expression of target genes to whose response elements NRs are bound. In Drosophila 18 NRs have been identified which have representative members belonging to each of the six major NR subfamilies, and which show a high degree of homology to their vertebrate counterparts. This fact, in addition to the power and ease of genetic manipulation, make Drosophila an excellent model system in which to study NR function. When I began my project, 17 of the 18 NRs in Drosophila were ‘orphan’ receptors for which no cognate ligand had been identified. As a first step in an effort to identify potential ligands for these 17 receptors I first set out to determine how, where and when nuclear receptors are regulated by small chemical ligands and/or their protein partners. In order to do so I contributed to developing a ‘ligand sensor’ system to visualize spatial activity patterns for each of the 18 Drosophila nuclear receptors in live, developing animals. This system is based upon transgenic lines that express the ligand binding domain of each Drosophila NR fused to the DNA-binding domain of yeast GAL4. When combined with a GAL4-responsive reporter gene, these fusion proteins show tissue- and stage-specific patterns of activation. Analysis using this system has revealed the stage and tissue specificity of NR activation for each of the fly NRs. The amnioserosa, yolk, midgut and fat body, which play major roles in lipid storage, metabolism and developmental timing, were identified as frequent sites of nuclear receptor activity. Dynamic changes in activation that are indicative of sweeping changes in ligand and/or co-factor production are also a prominent feature that has been revealed using this approach. In addition, I went on to characterize the ligand regulated function of a single Drosophila nuclear receptor, Ecdysone inducible protein 75 (E75). Previous work from our lab has demonstrated that E75 binds to heme, and that its function as a transcriptional repressor is regulated in vitro by binding of the small diatomic gases nitric oxide (NO) and carbon monoxide (CO) to its heme moiety. In an effort to validate and to further understand the in vivo relevance of E75 regulation by NO I used gain and loss of function transgenes, as well as tissues manipulated in culture to show that NO acts directly on the Drosophila nuclear receptor E75, reversing its ability to block the activity of its heterodimer partner Drosophila Hormone Receptor 3 (DHR3). By specifically focusing on the Drosophila larval ring gland, the principal endocrine organ responsible for the production of the metamorphosis-inducing hormone, ecdysone, I have shown that failure to produce NO and to inactivate E75 results in failure to recognize the signals that normally trigger metamorphosis.

Ng, Sin Man.
Thesis (Ph.D.)--Chinese University of Hong Kong, 2011.
Includes bibliographical references (leaves 96-104).
Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web.
Abstract also in Chinese.

The steroid hormone ecdysone plays vital roles during Drosophila development. Pulses of 20E during Drosophila life cycle function as temporal cues, signaling the onset of metamorphic processes, including the stage specific programmed cell death of larval tissues. Ecdysone is the critical developmental cue orchestrating the metamorphic reformation of CNS, resulting in the formation of adult-specific neural circuitry. Ecdysone signaling is transduced by a heterodimeric receptor complex formed between two nuclear receptors: EcR and Ultraspiracle (USP). There are 18 nuclear receptors known in Drosophila and EcR is the only receptor whose functions in neuronal PCD have been well recognized. Therefore, the current study is aimed to define the role of nuclear receptors in neuronal cell death mechanisms in Drosophila. Here, I examine the function of nuclear receptors in PCD of two groups of peptidergic neurons: vCrz and CCAP. EcR and USP receptor complex on activation results in the coordinated transcriptional regulation of a host of transcription factors regulating genes essential for PCD. USP plays a dual role in ecdysone response, as its function is necessary for both activation and repression of ecdysone primary response genes. I have developed a possible dominant-negative mutant USP (usp3), and expressed it in flies using the GAL4-UAS system to illustrate the role of USP in ecdysone mediated PCD of vCrz neurons. Targeted expression of usp3 in corazonin neurons results in a complete blockage of PCD pathway. Another interacting partner of USP, Drosophila Hormone Receptor 38, however shows no involvement in PCD of vCrz neurons. I have also designed an ecdysone sensor to monitor the developmental timing of EcR activation in vCrz neurons. Further, I investigate the survival factors required for preventing the untimely PCD of these two groups of neurons. The study reveals that DIAP1 is required for the survival of larval vCrz and CCAP neurons. Also, the nuclear receptor E75 is shown to be critical for preventing premature PCD of CCAP neurons.

Lui, Ki.
Thesis (M.Phil.)--Chinese University of Hong Kong, 2003.
Includes bibliographical references (leaves 163-171).
Abstracts in English and Chinese.
Abstract (English) --- p.i
Abstract (Chinese) --- p.v
Acknowledgements --- p.vii
Abbreviations --- p.ix
Table of Content --- p.x
Chapter Chapter 1. --- Introduction
Chapter 1.1 --- Overview and Endocrinology of hormones and hormone receptors --- p.1
Chapter 1.2 --- Hormone receptors: membrane bounded receptors --- p.3
Chapter 1.3 --- Hormone receptors: steroid nuclear receptors --- p.4
Chapter 1.4 --- "Estrogen, estrogen receptor alpha and beta (ERa, ERβ) and prostate gland" --- p.6
Chapter 1.5 --- Orphan nuclear receptors --- p.10
Chapter 1.6 --- The first orphan receptors identified-estrogen receptor related receptors --- p.12
Chapter 1.6.1 --- Estrogen receptor related receptor alpha (ERRα) --- p.13
Chapter 1.6.2 --- Estrogen receptor related receptor alpha (ERRβ) --- p.17
Chapter 1.6.3 --- Estrogen receptor related receptor alpha (ERRγ) --- p.19
Chapter 1.7 --- Aim of study --- p.21
Figure 1.1 Mechanism of activation of classical nuclear receptor by ligand --- p.23
Figure 1.2 Distribution of ERa and ERβ in human body --- p.24
Chapter Chapter 2. --- Methods and Materials
Chapter 2.1 --- Origin and supply of Noble rats --- p.25
Chapter 2.2 --- Cell culture
Chapter 2.2.1 --- Cell lines and culture media --- p.26
Chapter 2.2.2 --- Cell culture onto cover slips for immunohistochemistry --- p.27
Chapter 2.3 --- RNA preparation
Chapter 2.3.1 --- Total RNA extraction --- p.27
Chapter 2.3.2 --- mRNA extraction by Oligote´xёØ procedure --- p.29
Chapter 2.3.3 --- mRNA extraction by Fast Track 2.0 procedure --- p.30
Chapter 2.4 --- Molecular cloning by Rapid Amplification of cDNA Ends (RACE)
Chapter 2.4.1 --- Molecular cloning of rERRα --- p.31
Chapter 2.4.2 --- Molecular cloning of rERRβ --- p.36
Chapter 2.4.3 --- Molecular cloning of rERRγ --- p.42
Chapter 2.5 --- Molecular cloning into pCRII TOPO cloning vector --- p.47
Chapter 2.6 --- Sequencing analysis of DNA sequence by dRodamine® or BigDye® --- p.47
Chapter 2.7 --- DNA sequence analysis --- p.49
Chapter 2.8 --- Reverse transcription and RT-PCR --- p.49
Chapter 2.9 --- Southern blotting analysis
Chapter 2.9.1 --- Preparation of DNA blot membrane --- p.51
Chapter 2.9.2 --- Purification of DNA fragment from agarose gel for DIG-DNA labeling --- p.52
Chapter 2.9.3 --- Preparation of the DIG-labeled DNA probe --- p.53
Chapter 2.9.4 --- Membrane hybridization and colorimetric detection --- p.53
Chapter 2.10 --- In-situ hybridization histochemistry
Chapter 2.10.1 --- Linearization of DNA plasmid --- p.55
Chapter 2.10.2 --- Synthesis of riboprobe --- p.56
Chapter 2.10.3 --- Hybridization and detection --- p.56
Chapter 2.11 --- Western blotting analysis
Chapter 2.11.1 --- Protein extraction --- p.59
Chapter 2.11.2 --- Casting of SDS-PAGE electrophoresis --- p.59
Chapter 2.11.3 --- Polyacrylamide gel electrophoresis --- p.61
Chapter 2.11.4 --- Protein blotting analysis --- p.61
Chapter 2.12.1 --- Immunohistochemistry
Chapter 2.12.1 --- Histological preparation --- p.63
Chapter 2.12.2 --- Immunohistochemistry --- p.64
Table 1. List of culture media --- p.66
Table 2. Primer sequences for RACE-PCR --- p.67
Table 3. PCR conditions for RT-PCR --- p.68
Table 4. Primer sequences for RT-PCR --- p.68
Table 5. Reagent mixtures for linearization of the plasmid DNA --- p.69
Table 6. Riboprobe synthesis by in-vitro transcription --- p.70
Chapter Chapter 3. --- Results
Chapter 3.1 --- Cloning of full-length cDNA of rERRs by RACE-PCR --- p.71
Chapter 3.2 --- Cloning of full-length cDNA of rERRα from rat ovary cDNA library --- p.72
Chapter 3.3 --- Cloning of full-length cDNA of rERRβ from rat ventral prostate --- p.76
Chapter 3.4 --- Cloning of full-length cDNA of rERRγ from rat prostate --- p.80
Chapter 3.5 --- Expression distribution of ERRs detected by RT-PCR --- p.83
Chapter 3.6 --- mRNA expression of ERRs detected by in-situ hybridization --- p.86
Chapter 3.7 --- Protein expression of ERRa and ERRγ detected by western blotting --- p.87
Chapter 3.8 --- Expression of ERRa and ERRγ detected by immunohistochemistry --- p.88
Figure 3.1 Full-length DNA sequence of rERRα --- p.92
Figure 3.2 Predicted amino acid sequence of rERRα --- p.93
"Figure 3.3 DNA sequence alignment of rat, mouse and human ERRα" --- p.94
"Figure 3.4 Amino acid sequence alignment analysis of rat, mouse and human ERRα" --- p.95
Figure 3.5 Full-length DNA sequence of rERRβ --- p.96
Figure 3.6 Predicted amino acid sequence of rERRβ --- p.97
"Figure 3.7 DNA sequence alignment of rat, mouse and human ERRβ" --- p.98
"Figure 3.8 Amino acid sequence alignment analysis of rat, mouse and human ERRβ" --- p.99
Figure 3.9 Full-length DNA sequence of rERRγ --- p.100
Figure 3.10 Predicted amino acid sequence of rERRγ --- p.101
"Figure 3.11 DNA sequence alignment of rat, mouse and human ERRγ" --- p.102
"Figure 3.12 Amino acid sequence alignment analysis of rat, mouse and human ERRγ" --- p.103
Figure 3.13 Restriction enzyme cutting of full-length plasmids --- p.104
Figure 3.14 Expression pattern of rERRα in male sex accessory sex glands by RT-PCR --- p.105
Figure 3.15 Expression pattern of rERRα in urinary system and female sex organs by RT-PCR --- p.106
Figure 3.16 Tissue expression of rERRα by RT-PCR --- p.107
Figure 3.17 In-situ hybridization of ERRα in ovary --- p.108
Figure 3.18 Western blotting of ERRα --- p.109
Figure 3.19 Immunohistochemistry of ERRα in ovary --- p.110
Figure 3.20 Expression pattern of rERRβ in male sex accessory sex glands by RT-PCR --- p.111
Figure 3.21 Expression pattern of rERRβ in urinary system and female sex organs by RT-PCR --- p.112
Figure 3.22 Tissue expression of rERRβ by RT-PCR --- p.113
Figure 3.23 In-situ hybridization of ERRβ in rat prostate --- p.114
Figure 3.24 Negative control of in-situ hybridization of ERRβ in rat prostate --- p.115
Figure 3.25 Expression pattern of rERRγ in male sex accessory sex glands by RT-PCR --- p.116
Figure 3.26 Expression pattern of rERRy in urinary system and female sex organs by RT-PCR --- p.117
Figure 3.27 Tissue expression of rERRγ by RT-PCR --- p.118
Figure 3.28 Expression pattern of rERRγ in different prostatic cancer cell lines and xenografts by RT-PCR --- p.119
Figure 3.29 In-situ hybridization of ERRγ in rat prostate --- p.120
Figure 3.30 Negative control of in-situ hybridization of ERRβ in rat prostate --- p.121
Figure 3.31 Western blotting of ERRγ --- p.122
Figure 3.32 Immunohistochemistry of ERRγ in ERRy-transfected MCF-7 cells --- p.123
Figure 3.33 Immunohistochemistry of ERRγ in ventral prostate of rat --- p.124
Figure 3.34 Immunohistochemistry of ERRγ in lateral prostate of rat --- p.125
Figure 3.35 Immunohistochemistry of ERRγ in dorsal prostate of rat --- p.126
Figure 3.36 Immunohistochemistry of ERRγ in testis of rat --- p.127
Figure 3.37 Immunohistochemistry of ERRγ in epididymis of rat --- p.128
Figure 3.38 Immunohistochemistry of ERRγ in brown adipose tissues of rat --- p.129
Figure 3.39 Immunohistochemistry of ERRγ in brain of rat --- p.130
Figure 3.40 Immunohistochemistry of ERRγ in brain of rat --- p.131
Chapter Chapter 4. --- Discussion
Chapter 4.1 --- Sequence analysis of the full-length cDNA sequences of the rat estrogen receptor-related receptors (ERRs) --- p.132
Chapter 4.2 --- Ligand independence and constitutive self-activation of estrogen receptor-related receptors --- p.133
Chapter 4.3 --- Board expression pattern of estrogen receptor-related receptors --- p.138
Chapter 4.3.1 --- Board expression pattern of estrogen receptor-related receptor alpha --- p.138
Chapter 4.3.2 --- Board expression pattern of estrogen receptor-related receptor beta --- p.140
Chapter 4.3.3 --- Board expression pattern of estrogen receptor-related receptor gamma --- p.141
Chapter 4.4 --- Expression of ERRs in the prostate gland --- p.143
Chapter 4.5 --- Expression of ERRs in the prostatic cell lines and cancer xenografts --- p.147
Chapter 4.6 --- Expression of ERRs in the ERRγ-transfected MCF-7 cells --- p.149
Chapter 4.7 --- Expression of ERRs in the testis and epididymis --- p.149
Chapter 4.8 --- Expression of ERRs in the adipose tissue --- p.150
Chapter 4.9 --- Expression of ERRs in the ovary --- p.151
Chapter 4.10 --- Expression of ERRs in the brain --- p.153
Figure 5.1 Map of full-length clone of rERRα --- p.155
Figure 5.2 Map of full-length clone of rERRβ --- p.156
Figure 5.3 Map of full-length clone of rERRα --- p.157
Figure 5.4 Comparison of the homology of amino acid sequences amongst ERs and ERRs --- p.158
Figure 5.5 Phylogeny tree of nuclear receptors --- p.159
Figure 5.6 Relationship of different prostatic cell lines and xenografts --- p.160
Chapter Chapter 5. --- Summary --- p.161
References --- p.163-171

Saccharomyces cerevisiae are unicellular organisms that are highly adaptable to acute changes in nutrient availability. The two main signaling pathways that allow S. cerevisiae to sense and respond to changes in glucose availability in the environment are the conserved cAMP/PKA and AMPK/Snf1 kinase-dependent pathways. The conserved TORC1 pathway is primarily responsible for allowing cells to respond to the availability of nitrogen. Studies have shown that S. cerevisiae, but not mammalian and plant cells, regulate nuclear tRNA trafficking in response to nutrient stress. Here, we show that the yeast species of the Saccharomyces genus, but not Schizosaccharomyces pombe and Kluyveromyces lactis specifically regulate nuclear tRNA export in response to nutrient stress, providing further evidence that regulation of nuclear tRNA export in response to nutrient availability is not evolutionarily conserved. We also established that amino acid and nitrogen starvation affects nuclear export of a subset of tRNAs in S. cerevisiae. Inhibition of TORC1 signaling by rapamycin treatment, which simulates nitrogen starvation, also affects nuclear export of the same subset of tRNAs, suggesting that the TORC1 signaling pathway plays a role in regulating nuclear export of the tRNAs in response to nitrogen level. Regulation of nuclear export of these tRNAs by nitrogen deprivation is most likely due to an effect on the function of the nuclear tRNA export receptors, as overexpression of the tRNA export receptor, Los1p, restores export of the tRNAs during nitrogen starvation. These findings suggest that the TORC1 signaling pathway may, in part, regulate nuclear export of the tRNAs by affecting the function of the tRNA export receptors. In contrast to amino acid and nitrogen starvation, glucose depletion affects nuclear export of all tRNA species in S. cerevisiae. Evidence obtained suggests that nuclear retention of tRNA in cells deprived of glucose is due to a block in nuclear re-import of the nuclear tRNA export receptors. Retention of the receptors in the cytoplasm is not caused by activation of Snf1p, but by the inactivation of PKA during glucose deprivation. Furthermore, regulation of nuclear re-import of the receptors is not due to phosphorylation of the tRNA export receptors by PKA. However, PKA phosphorylates known components of the tRNA export machinery. A model that is consistent with the data is that PKA and an unknown mechanism regulate the activity of these components or an unidentified protein(s) to control nuclear re-import of the receptors in response to glucose availability.

Background and aims of the study. Prostate cancer (PCa) is one of the most common hormone-dependent cancers in men in Western and also Asian countries. The standard treatment options for localized PCa include surgery and androgen-deprivation therapy (ADT). However, most patients upon ADT therapy invariably relapse and progress to a more aggressive and metastatic stage termed as castration-resistant PCa (CRPC). Accumulating studies indicate that androgen receptor (AR) transcriptional activity is dysregulated during the advanced progression of CRPC. One important mechanism responsible for the growth of CRPC includes increased intra-tumoral androgen synthesis in PCa. Recently, a novel androgen-responsive fusion gene TMPRSS2:ERG formed by fusion between the transmembrane protein TMPRSS2 and transcription factor ERG, has been identified in approximately 50% PCa samples, which results in the aberrant expression of ERG function as oncogenic factor in PCa. Currently, TMPRSS2:ERG is regarded as a significant potential diagnostic and prognostic biomarker for PCa. Estrogen-related receptor alpha-ERRα, the first identified ligand-independent orphan nuclear receptor, is characterized to be up-regulated in advanced cancers, suggesting that ERRα might play important regulatory roles in the malignant progression of PCa. Previous studies showed that ERRα can functionally cross-talk with AR signaling via co-targeting to AR targets and regulate the expression of some steroidogenic enzymes in breast cancer. Based on this background, it is hypothesized that ERRα could functionally regulate the TMPRSS2:ERG fusion gene and play a regulatory role in the development and progression of CRPC through activation of the intracellular androgen synthesis pathway.
Results. 1) The results obtained in this study showed that suppression of ERRα by its specific inverse agonist XCT790 or shRNA-knockdown could induce down-regulation of TMPRSS2:ERG and also its target genes in AR-positive VCaP PCa cells. 2) Ectopic expression of ERRα and/or its coactivator PGC-1α could increase the expression of TMPRSS2:ERG in AR-negative NCI-H660 PCa cells. 3) Two ERRα-DNA binding elements were identified by ChIP assay and sequence analysis in the promoter of TMPRSS2:ERG and both of these two elements could be transactivated by ERRα and PGC-1α. 4) Ectopic expression of TMPRSS2:ERG under the regulation of ERRα enhanced the prostatic cell invasion capacity as shown in the TMPRSS2:ERG infectants of BPH-1 and PC-3 prostatic cells. 5) ERG expressed by the TMPRSS2:ERG fusion could directly transactivate the ERRα gene in prostatic cells. 6) A positive correlation on the expressions between TMPRSS2:ERG and ERRα was demonstrated in a xenograft model of CRPC (VCaP-CRPC). 7) The expression of TMPRSS2:ERG and ERRα showed significant up-regulation and the transactivation activity of ERRα was also enhanced in castration-resistant VCaP-CRPC cells. 8) Ectopic expression of ERRα could promote resistant growth capacity to androgen-deprivation condition in LNCaP PCa cells, whereas shRNA-mediated silence of ERRα could weaken this resistant capacity. Furthermore, ectopic expression of ERRα in LNCaP-ERRα infectants could promote their in vivo growth resistance to castration in SCID mice. 9) Expression of several androgenic enzyme genes, including CYP11A1, CYP17A1 and ARK1C3, were detected to be up-regulated in castration-resistant VCaP-CRPC cells. Moreover, ectopic expression of ERRα could induce the increased expression of these enzyme genes in LNCaP-ERRα infectants, whereas knockdown of ERRα by shRNA could decrease their expression. 10) ERRα could directly transactivate the gene promoters of CYP11A1, CYP17A1 and ARK1C3 which contain ERRE elements prediction by sequence analysis. These results suggested that ERRα could play a role in de novo or intra prostatic androgen synthesis in the PCa cells.
Conclusions. The results obtained in this study suggested that ERRα and TMPRSS2:ERG could form a positive reciprocal loop in PCa cells, and ERRα could also promote the resistant growth capacity of PCa cells resistant to the androgen-deprivation condition in vitro and also castration-resistant growth in vivo via a mechanism of up-regulation of androgenic enzyme genes. The results also suggested that ERRα might play a significant regulatory role in the development and progression of PCa, particularly the advanced CRPC, and also ERRα could be a potential therapeutic target for the treatment of PCa, particularly the advanced PCa-CRPC.
研究背景與研究目的：前列腺癌作為激素依賴的一種癌症，經常出現在西方和亞洲國家的男性人群中。對於局限性前列腺癌多採用外科手術和去勢的治療。但是大多數病人經過去勢治療后會再次復發並且形成更加惡心幾轉移的前列腺癌，稱之為去勢難治性前列腺癌（CRPC）。越來越多的研究表明在去勢難治性前列腺癌發病過程中，雄激素受體轉錄活性異性增強。其中一個重要機理解釋為前列腺癌細胞自身合成的雄激素增多。進來，在大約50%的前列腺癌病人中新檢測到一個受雄激素受（AR）體調控的融合基因TMPRSS2:ERG，它是由稱為TMPRSS2的一個跨膜蛋白和一個稱為ERG的轉錄因子融合而成，它的出現導致了在前列腺癌中異常的稱為致癌因子的ERG蛋白的高表達。目前，TMPRSS2:ERG已經被作為一個重要的潛在的診斷和預測的標誌物應用在前列腺癌中。作為第一個鑒定的配體不依賴的孤兒受體-ERRα，被證明在晚期的癌症中有很高的表達，預示著ERRα可能在惡性的癌症中起到一個非常重要的調控作用。之前的研究表明通過共同調控AR的下游基因，ERRα同AR信號通路之間有功能性的交叉調控；除此之外，在乳腺癌中，ERRα還可以調控一些類固醇類化合物的合成相關的一些酶的合成。依據上述，我們推定ERRα可能功能性地調控TMPRSS2:ERG融合基因的表達並且通過調控細胞內的雄激素的合成進而在去勢難治性前列腺癌的發生和發展中起到一個非常重要的作用。
結果：本論文研究結果總結如下：1）在有AR表達的前列腺癌細胞-VCaP細胞中，通過ERRα特異性的抑制劑XCT790處理或者shRNA介入的干擾ERRα的mRNA的方法來抑制ERRα，下調了TMPRSS2:ERG和它的一些下游調控基因的表達。2）在沒有AR表達的前列腺癌細胞-NCI-H660細胞中，上調ERRα或者它的特異性的共激活因子PGC-1α表達可以提升TMPRSS2:ERG的表達。3）通過ChIP實驗，在TMPRSS2:ERG的啟動子上面，兩個ERRα的DNA結合位點被鑒定出來。並且這兩個位點可以被ERRα和PGC-1α轉錄激活。4）在兩個前列腺細胞BPH-1和PC-3細胞中，在ERRα的調控下高表達TMPRSS2:ERG融合基因可以增強細胞的侵襲能力。5）融合基因TMPRSS2:ERG導致的ERG蛋白的表達可以直接轉錄激活ERRα的表達。6）我們通過VCaP細胞的異種移植建立VCaP-CRPC的體內模型來模擬CRPC過程，在整個過程中，我們發現TMPRSS2:ERG和ERRα有一致性的表達相關性。除此之外，我們根據上述動物模型通建立了VCaP-CRPC細胞系，並且發現在VCaP-CRPC細胞細胞中，TMPRSS2:ERG和ERRα都有被上調並且ERRα的轉錄活性同樣也提升。7）在LNCaP細胞中高表達ERRα可以提升細胞在去除雄激素的環境中生長的能力。但是當在LNCaP細胞中用shRNA干擾掉ERRα可以明顯減弱這種生長的能力。用LNCaP-ERRα穩轉ERRα的細胞異種移植建立SCID老鼠體內腫瘤模型，我們發現和LNCaP-pBABE對照組相比，LNCaP-ERRα細胞生長的更快更大。並且在對老鼠進行睪丸切除術后，LNCaP-ERRα組細胞更快適應這種環境并繼續生長，相比之下，LNCaP-pBABE對照組則持續萎縮減小。8）在上述的VCaP-CRPC細胞中，我們發現一些和雄激素合成相關的關鍵的酶包括CYP11A1，CYP17A1和ARK1C3的表達量有顯著地提升。而且在LNCaP-ERRα細胞中同樣檢測到這些酶的表達量的提升。然而當在LNCaP細胞中用shRNA干擾掉ERRα可以明顯減降低上述酶的表達。9）我們在CYP11A1，CYP17A1和ARK1C3基因的啟動子區域發現有ERRα結合位點，並且發現這些位點可以被ERRα轉錄激活。
結論：本論文的研究結果提示在前列腺癌細胞中，ERRα和TMPRSS2:ERG可以形成一個相互正向調控的循環。除此之外，上調ERRα可以促進細胞在去除雄激素的環境中生長的能力，並且在動物體內可以提升細胞在睪丸去除的環境中的適應和生長能力。這種體內和體外的能力的提升是通過一種潛在的上調前列腺癌細胞的雄激素合成相關的關鍵的酶的表達，進而提升雄激素的含量而得以實現的。上述的結果預示著ERRα可能在前列腺癌發生機發展的過程中起到非常重要的調控作用，尤其在晚期的CRPC中。同時，ERRα也可能作為一個潛在的重要的前列腺癌尤其是晚期的CRPC的治療靶點，尤其是一些潛在ERRα的特異性抑制劑，比如XCT790，可能作為將來用以作為治療前列腺癌的特異性靶點藥物。
Xu, Zhenyu.
Thesis Ph.D. Chinese University of Hong Kong 2014.
Includes bibliographical references (leaves 126-143).
Abstracts also in Chinese.
Title from PDF title page (viewed on 05, October, 2016).
Xu, Zhenyu.
Detailed summary in vernacular field only.
Detailed summary in vernacular field only.
Detailed summary in vernacular field only.

Estrogen-receptor-related receptor gamma, ERRγ, is highly expressed in cartilage and upregulates the chondrogenic transcription factor, Sox9, in a chondrocytic cell line. To assess the effect of increasing ERRγ activity on cartilage in vivo, we generated transgenic animals driving ERRγ expression with a chondrocyte-specific promoter. I verified that one transgenic line exhibited 26% increased ERRγ protein at E14.5. No major morphological defects were seen at this stage, but I observed significant reduction in the size of the appendicular skeleton in P7 mice, such that all elements of the appendicular skeleton were significantly reduced by 4 – 10%. I continued the phenotype analysis at the histological level and found that the P7 animals displayed significantly reduced growth plate height, caused by deficiencies in the size of the proliferative and hypertrophic zones of the growth plate. This suggests a previously unknown role for ERRγ in regulating endochondral ossification in growth plate chondrocytes.