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Coactivator
Kinds of Coactivator Selected AbstractsA High-Resolution Interaction Map of Three Transcriptional Activation Domains with a Key Coactivator from Photo-Cross-Linking and Multiplexed Mass Spectrometry,ANGEWANDTE CHEMIE, Issue 38 2009Chinmay Jeder auf seine Weise: Die Wechselwirkungszentren von drei prototypischen amphipathischen Transkriptionsaktivatoren (siehe die verschiedenfarbigen Helices im Bild) am Coaktivator Med15 wurden durch photoinduzierte Vernetzung mit anschließenden ESI- und MALDI-MS-Messungen aufgeklärt. Studien der funktionellen Relevanz dieser Zentren in Hefe ergaben überlappende, aber dennoch charakteristische Bindungsmuster der Aktivatoren. [source] Oestradiol and SERM treatments influence oestrogen receptor coregulator gene expression in human skeletal muscle cellsACTA PHYSIOLOGICA, Issue 3 2009C. M. Dieli-Conwright Abstract Aim:, Oestrogen receptors (ER) are present in human skeletal muscle (hSkM) cells; however, the function of the receptor is currently unknown. We investigated the influence of oestradiol and selective ER modulators [tamoxifen (TAM), raloxifene (RAL)] on ER coregulator mRNA expression in hSkM. Methods:, Human skeletal muscle cells were treated with 10 nm oestradiol, 5 ,m TAM and 10 ,m RAL over a 24-h period. Following the treatment period, mRNA expression was quantified using real-time PCR to detect changes in ER-,, ER-,, steroid receptor coactivator (SRC), silencing mediator for retinoid and thyroid hormone receptors (SMRT), MyoD, GLUT4 and c-fos. Results:, ER-, mRNA expression increased with all three drug treatments (P < 0.05) while there was no change in mRNA expression of ER-, in hSkM cells. mRNA expression of SRC increased and SMRT decreased with oestradiol, TAM and RAL in hSkM cells (P < 0.05). Importantly, mRNA expression of MyoD increased with oestradiol and decreased with TAM and RAL in hSkM cells (P < 0.05). mRNA expression of GLUT4 increased with oestradiol and RAL and decreased with TAM in hSkM cells (P < 0.05). Conclusions:, These findings are novel in that they provide the first evidence that oestradiol and selective ER modulators influence ER-, function in hSkM cells. This demonstrates the importance of the ER and alterations in its coregulators, to potentially prevent sarcopenia and promote muscle growth in postmenopausal women using these forms of hormone replacement therapy. [source] The sexually dimorphic expression of L7/SPA, an estrogen receptor coactivator, in zebra finch telencephalonDEVELOPMENTAL NEUROBIOLOGY, Issue 14 2007Kelli A. Duncan Abstract Sex differences in the zebra finch (Taeniopygia guttata) brain are robust and include differences in morphology (song control nuclei in males are significantly larger) and behavior (only males sing courtship songs). In zebra finches, hormonal manipulations during development fail to reverse sex differences in song nuclei size and suggest that the classical model of sexual differentiation is incomplete for birds. Coactivators act to initiate transcriptional activity of steroid receptors, and may help explain why hormonal manipulations alone are not sufficient to demasculinize the male zebra finch brain. The present study investigated the expression and localization of L7/SPA (an estrogen receptor coactivator) mRNA and protein expression across the development of zebra finch song nuclei from males and females collected on P1 (song nuclei not yet formed), P10 (posthatch day 10, song nuclei formed), P30 (30 days posthatch, sexually immature but song nuclei formed and birds learning to sing), and adult birds (older than 65 days and sexually mature). Northern blot analysis showed a significant sex difference in P1 and adult L7/SPA mRNA expression while Western blot analysis also showed enhanced expression in the male brain at all age points. Both in situ hybridization and immunohistochemistry demonstrated that L7/SPA mRNA and protein were located in the song nuclei as well as expressed globally. Elevated coactivator expression may be a possible mechanism controlling the development of male song control nuclei, and coactivators such as L7/SPA may be important regulators of the masculinizing effects of estradiol on brain sexual differentiation. © 2007 Wiley Periodicals, Inc. Develop Neurobiol, 2007. [source] The proteasome inhibitor bortezomib inhibits FGF-2-induced reduction of TAZ levels in osteoblast-like cellsEUROPEAN JOURNAL OF HAEMATOLOGY, Issue 1 2010Homare Eda Abstract Objectives:,Bortezomib (PS-341; VelcadeÔ), a proteasome inhibitor, is used as a therapeutic agent for multiple myeloma. Bortezomib has been shown to strongly induce osteoblast differentiation and elevate the levels of osteoblast-related differentiation markers in the serum of patients with myeloma. Bortezomib also reportedly increases the activity of the transcription factor, Runx2. However, the mechanism of action by which bortezomib-elevated Runx2 activity mediates osteoblast differentiation remains unclear. On the other hand, fibroblast growth factor 2 (FGF-2) is found at high levels in patients with multiple myeloma. We previously reported that FGF-2 reduces the levels of the transcriptional coactivator with PDZ-binding motif (TAZ). We therefore investigated the effects of bortezomib on TAZ protein levels in the presence of FGF-2. Methods: Osteoblastic MC3T3-E1 cells were treated with different concentrations of bortezomib in the presence or absence of FGF-2 and various biologic responses were investigated by immunoblotting, RT-PCR, quantitative PCR, and alizarin red staining. Results: We found that bortezomib inhibited FGF-2-induced reduction of TAZ levels through a pathway other than that used for proteasome inhibition, while maintaining TAZ function, which in turn, enhanced the expression of Runx2-transcribed osteogenic differentiation markers. Bortezomib also suppressed the antimineralization effect of FGF-2. Conclusions: These findings suggest that bortezomib inhibited FGF-2-induced reduction of TAZ and consequently stimulated osteogenic differentiation independently of proteasome inhibition. These findings may contribute to elucidate the osteolytic mechanism in multiple myeloma, and to the development of new drugs for multiple myeloma and other osteolytic diseases. [source] Comparative distribution of the mammalian mediator subunit thyroid hormone receptor-associated protein (TRAP220) mRNA in developing and adult rodent brainEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 4 2002Anastasia Galeeva Abstract TRAP220 (thyroid hormone receptor-associated protein) is a recently cloned nuclear receptor coactivator, which interacts with several nuclear receptors in a ligand-dependent manner and stimulates transcription by recruiting the TRAP mediator complex to hormone responsive promoter regions. TRAP220 has been shown to interact with thyroid hormone receptors, vitamin D receptors, peroxisome proliferator-activated receptors, retinoic acid receptors and oestrogen receptors. Thyroid hormone and retinoic acid play very important roles in brain development and they also influence adult brain. Using in situ hybridization we have examined expression of TRAP220 mRNA in the central nervous system during development and in adult rat and mouse brain. Expression of TRAP220 was seen already during early embryonic development in the epithelium of neural tube at E9 in mouse and at E12 in rat. At later stages of development the strongest signal was seen in different layers of cerebral neocortex, external germinal layer of cerebellum, differentiating fields of hippocampus and neuroepithelium, and a moderate signal was detected in basal ganglia, different areas of diencephalon and midbrain. In adult rat brain the signal was more restricted than during development. TRAP220 expression occurred mostly in the granular layer of cerebellar cortex, piriform cortex and hippocampal formation. The signal was found predominantly in neurons. Our work supports the assumption that TRAP220 plays an important role in growth and differentiation of central nervous system and may have a function in certain areas of adult brain. [source] Aly/,REF, a factor for mRNA transport, activates RH gene promoter functionFEBS JOURNAL, Issue 11 2005Hiroshi Suganuma The rhesus (Rh) blood group antigens are of considerable importance in transfusion medicine as well as in newborn or autoimmune hemolytic diseases due to their high antigenicity. We identified a major DNaseI hypersensitive site at the 5, flanking regions of both RHD and RHCE exon 1. A 34 bp fragment located at ,191 to ,158 from a translation start position, and containing the TCCCCTCCC sequence, was involved in enhancing promoter activity, which was assessed by luciferase reporter gene assay. A biotin-labelled 34 bp probe isolated an mRNA transporter protein, Aly/REF. The specific binding of Aly/REF to RH promoter in erythroid was confirmed by chromatin immunoprecipitation assay. The silencing of Aly/REF by siRNA reduced not only the RH promoter activity of the reporter gene but also transcription from the native genome. These facts provide second proof of Aly/REF as a transcription coactivator, initially identified as a coactivator for the TCR, enhancer function. Aly/REF might be a novel transcription cofactor for erythroid-specific genes. [source] Repressive domain of unliganded human estrogen receptor , associates with Hsc70GENES TO CELLS, Issue 12 2005Satoko Ogawa Estrogen receptor (ER) is a hormone-inducible transcription factor as a member of the nuclear receptor gene superfamily. Unliganded ER is transcriptionally silent and capable of DNA binding; however, it is unable to suppress the basal activity of the target gene promoters, unlike non-steroid hormone receptors that associate with corepressors in the absence of their cognate ligands. To study the molecular basis of how unliganded human ER, is maintained silent in gene regulation upon the target gene promoters, we biochemically searched interactants for hER,, and identified heat shock protein 70 (Hsc70). Hsc70 appeared to associate with the N-terminal hormone binding E domain, that also turned out a transcriptionally repressive domain. Competitive association of Hsc70 with a best known coactivator p300 was observed. Thus, these findings suggest that Hsc70 associates with unliganded hER,, and thereby deters hER, from recruiting transcriptional coregulators, presumably as a component of chaperone complexes. [source] Molecular mechanism of a cross-talk between oestrogen and growth factor signalling pathwaysGENES TO CELLS, Issue 8 2000Shigeaki Kato Oestrogen (E2) plays significant roles in variety of biological events such as the development and maintenance of female reproductive organs, bone and lipid metabolisms. More recently, from study of knock-out mice deficient in oestrogen receptor (ER) , and ER, it turned out that normal spermatogenesis requires the E2 actions. Furthermore, this female steroid hormone is also well known to be deeply involved in many pathophysiological events such as osteoporosis and cancer development in female reproductive organs. It is particularly well known that most breast cancer is dependent on E2 in its development. Such E2 actions are thought to be mediated through two subtypes of ERs. Growth factors have been shown to synergize in this E2 signalling pathway, although the actual molecular mechanism largely remains unknown. Recently, we found that the MAP kinase activated by growth factors phosphorylates the Ser118 residue of the human ER, A/B domain and this phosphorylation potentiates the N-terminal transactivation function (AF-1) of human ER,, indicating the possible molecular mechanism of a novel cross-talk between E2 and growth factor signalling pathways. More recently, we have identified a coactivator associating with the hER, AF-1 in a MAPK-mediated phosphorylation-dependent manner. In this review, the molecular mechanism of this cross-talk is discussed in terms of the transactivation function of ERs, and their coactivators. [source] Identification of amplified and expressed genes in breast cancer by comparative hybridization onto microarrays of randomly selected cDNA clonesGENES, CHROMOSOMES AND CANCER, Issue 1 2002Jeremy Clark Microarray analysis using sets of known human genes provides a powerful platform for identifying candidate oncogenes involved in DNA amplification events but suffers from the disadvantage that information can be gained only on genes that have been preselected for inclusion on the array. To address this issue, we have performed comparative genome hybridization (CGH) and expression analyses on microarrays of clones, randomly selected from a cDNA library, prepared from a cancer containing the DNA amplicon under investigation. Application of this approach to the BT474 breast carcinoma cell line, which contains amplicons at 20q13, 17q11,21, and 17q22,23, identified 50 amplified and expressed genes, including genes from these regions previously proposed as candidate oncogenes. When considered together with data from microarray expression profiles and Northern analyses, we were able to propose five genes as new candidate oncogenes where amplification in breast cancer cell lines was consistently associated with higher levels of RNA expression. These included the HB01 histone acetyl transferase gene at 17q22,23 and the TRAP100 gene, which encodes a thyroid hormone receptor-associated protein coactivator, at 17q11,21. The results demonstrate the utility of this microarray-based CGH approach in hunting for candidate oncogenes within DNA amplicons. © 2002 Wiley-Liss, Inc. [source] Abnormal lens morphogenesis and ectopic lens formation in the absence of ,-catenin function,GENESIS: THE JOURNAL OF GENETICS AND DEVELOPMENT, Issue 4 2007Jana Kreslova Abstract ,-Catenin plays a key role in cadherin-mediated cell adhesion as well as in canonical Wnt signaling. To study the role of ,-catenin during eye development, we used conditional Cre/loxP system in mouse to inactivate ,-catenin in developing lens and retina. Inactivation of ,-catenin does not suppress lens fate, but instead results in abnormal morphogenesis of the lens. Using BAT-gal reporter mice, we show that ,-catenin-mediated Wnt signaling is notably absent from lens and neuroretina throughout eye development. The observed defect is therefore likely due to the cytoskeletal role of ,-catenin, and is accompanied by impaired epithelial cell adhesion. In contrast, inactivation of ,-catenin in the nasal ectoderm, an area with active Wnt signaling, results in formation of crystallin-positive ectopic lentoid bodies. These data suggest that, outside of the normal lens, ,-catenin functions as a coactivator of canonical Wnt signaling to suppress lens fate. genesis 45:157,168, 2007. Published 2007 Wiley-Liss, Inc. [source] Combined R-,,lipoic acid and acetyl-L-carnitine exerts efficient preventative effects in a cellular model of Parkinson's diseaseJOURNAL OF CELLULAR AND MOLECULAR MEDICINE, Issue 1-2 2010Hongyu Zhang Abstract Mitochondrial dysfunction and oxidative damage are highly involved in the pathogenesis of Parkinson's disease (PD). Some mitochondrial antioxidants/nutrients that can improve mitochondrial function and/or attenuate oxidative damage have been implicated in PD therapy. However, few studies have evaluated the preventative effects of a combination of mitochondrial antioxidants/nutrients against PD, and even fewer have sought to optimize the doses of the combined agents. The present study examined the preventative effects of two mitochondrial antioxidant/nutrients, R-,,lipoic acid (LA) and acetyl-L-carnitine (ALC), in a chronic rotenone-induced cellular model of PD. We demonstrated that 4-week pretreatment with LA and/or ALC effectively protected SK-N-MC human neuroblastoma cells against rotenone-induced mitochondrial dysfunction, oxidative damage and accumulation of ,-synuclein and ubiquitin. Most notably, we found that when combined, LA and ALC worked at 100,1000-fold lower concentrations than they did individually. We also found that pretreatment with combined LA and ALC increased mitochondrial biogenesis and decreased production of reactive oxygen species through the up-regulation of the peroxisome proliferator-activated receptor-, coactivator 1, as a possible underlying mechanism. This study provides important evidence that combining mitochondrial antioxidant/nutrients at optimal doses might be an effective and safe prevention strategy for PD. [source] Integrative nuclear FGFR1 signaling (INFS) as a part of a universal "feed-forward-and-gate" signaling module that controls cell growth and differentiationJOURNAL OF CELLULAR BIOCHEMISTRY, Issue 4 2003Michal K. Stachowiak Abstract A novel signaling mechanism is described through which extracellular signals and intracellular signaling pathways regulate proliferation, growth, differentiation, and other functions of cells in the nervous system. Upon cell stimulation, fibroblast growth factor receptor-1 (FGFR1), a typically plasma membrane-associated protein, is released from ER membranes into the cytosol and translocates to the cell nucleus by an importin-,-mediated transport pathway along with its ligand, FGF-2. The nuclear accumulation of FGFR1 is activated by changes in cell contacts and by stimulation of cells with growth factors, neurotransmitters and hormones as well as by a variety of different second messengers and thus was named integrative nuclear FGFR1 signaling (INFS). In the nucleus, FGFR1 localizes specifically within nuclear matrix-attached speckle-domains, which are known to be sites for RNA Pol II-mediated transcription and co-transcriptional pre-mRNA processing. In these domains, nuclear FGFR1 colocalizes with RNA transcription sites, splicing factors, modified histones, phosphorylated RNA Pol II, and signaling kinases. Within the nucleus, FGFR1 serves as a general transcriptional regulator, as indicated by its association with the majority of active nuclear centers of RNA synthesis and processing, by the ability of nuclear FGFR1 to activate structurally distinct genes located on different chromosomes and by its stimulation of multi-gene programs for cell growth and differentiation. We propose that FGFR1 is part of a universal "feed-forward-and-gate" signaling module in which classical signaling cascades initiated by specific membrane receptors transmit signals to sequence specific transcription factors (ssTFs), while INFS elicited by the same stimuli feeds the signal forward to the common coactivator, CREB-binding protein (CBP). Activation of CBP by INFS, along with the activation of ssTFs by classical signaling cascades brings about coordinated responses from structurally different genes located at different genomic loci. © 2003 Wiley-Liss, Inc. [source] PSMD9 gene variants within NIDDM2 may rarely contribute to type 2 diabetesJOURNAL OF CELLULAR PHYSIOLOGY, Issue 3 2007C. Gragnoli Multiple genome-wide scans in different populations have linked the chromosome 12q24 region, known as NIDDM2 (non-insulin-dependent-diabetes, locus 2), to type 2 diabetes. Within NIDDM2 we examined the PSMD9 (proteasome modulator 9/Bridge-1) gene that encodes a PDZ-domain transcriptional coactivator of insulin production. Our goal was to identify a potential contribution of the PSMD9 gene to type 2 diabetes in Italians. We directly sequenced the entire gene PSMD9 in Italian type 2 diabetes patients (n,=,237) and controls subjects (n,=,215) and performed an association study with the identified gene variants. We found five single nucleotide polymorphisms (SNPs), A17V, IVS1+nt29, IVS3+nt460, IVS3+nt437, and E197G, which are not associated with disease in our case,control study. Furthermore, we identified two PSMD9 gene variants in type 2 diabetes patients, which produced nonconservative amino acid substitutions S143G and N166S within the PDZ domain and two other gene variants. Three out of four of these variants are absent from the control subjects screened. We propose that the three PSMD9 gene variants (S143G, N166S and G,>,A at IVS3+nt102), absent in control subjects, contribute rarely to late-onset type 2 diabetes in Italians. In fact, the frequency rate of such variants in unrelated cases equals 0.016. We may not exclude that PSMD9 gene variants may contribute, either commonly or rarely, to an increased risk of type 2 diabetes in other populations. J. Cell. Physiol. 212:568,571, 2007. © 2007 Wiley-Liss, Inc. [source] cAMP-induced differentiation of human neuronal progenitor cells is mediated by nuclear fibroblast growth factor receptor-1 (FGFR1)JOURNAL OF NEUROCHEMISTRY, Issue 6 2003E. K. Stachowiak Abstract Activation of cAMP signaling pathway and its transcriptional factor cyclic AMP response element binding protein (CREB) and coactivator are key determinants of neuronal differentiation and plasticity. We show that nuclear fibroblast growth factor receptor-1 (FGFR1) mediates cAMP-induced neuronal differentiation and regulates CREB and CREB binding protein (CBP) function in ,-internexin-expressing human neuronal progenitor cells (HNPC). In proliferating HNPC, FGFR1 was associated with the cytoplasm and plasma membrane. Treatment with dB-cAMP induced nuclear accumulation of FGFR1 and caused neuronal differentiation, accompanied by outgrowth of neurites expressing MAP2 and neuron-specific neurofilament-L protein and enolase. HNPC transfected with nuclear/cytoplasmic FGFR1 or non-membrane FGFR1(SP-/NLS), engineered to accumulate exclusively in the cell nucleus, underwent neuronal differentiation in the absence of cAMP stimulation. In contrast, FGFR1/R4, with highly hydrophobic transmembrane domain of FGFR4, was membrane associated, did not enter the nucleus and failed to induce neuronal differentiation. Transfection of tyrosine kinase-deleted dominant negative receptor mutants, cytoplasmic/nuclear FGFR1(TK-) or nuclear FGFR1(SP-/NLS)(TK-), prevented cAMP-induced neurite outgrowth. Nuclear FGFR1 localized in speckle-like domains rich in phosphorylated histone 3 and splicing factors, regions known for active RNA transcription and processing, and activated the neurofilament-L gene promoter. FGFR1(SP-/NLS) transactivated CRE, up-regulated phosphorylation and transcriptional activity of CREB and stimulated the activity of CBP several-fold. Thus, cAMP-induced nuclear accumulation of FGFR1 provides a signal that triggers molecular events leading to neuronal differentiation. [source] Oestrogen Receptors, Receptor Variants and Oestrogen Actions in the Hypothalamic-Pituitary AxisJOURNAL OF NEUROENDOCRINOLOGY, Issue 2 2002M. A. Shupnik Abstract Information on oestrogen action has grown exponentially in the past decade, and recent studies have begun to define the mechanism of ligand-dependent activation and cell-specific effects. Oestrogen-mediated gene transcription in a specific tissue depends on several factors, the most important of which is the presence of at least one of the two nuclear oestrogen receptor (ER) isoforms, ER, and ER,. The presence and levels of specific ER isoform variants, along with receptor coactivator, corepressor and integrator proteins, directly modulate overall nuclear ER activity. The structure of the ligand, including both physiological oestrogens and synthetic oestrogen receptor modulators, influences ER interactions with these other proteins and thus determines the biological response. Furthermore, peptide and neurotransmitter-stimulated intracellular signalling pathways activate specific enzyme cascades and may modify the receptors and their interacting proteins, resulting in either independent or ligand-enhanced ER-mediated responses. Finally, several rapid effects of oestrogen probably occur at the membrane through nongenomic pathways that may or may not require the same ER proteins that are found in the nucleus. This review concentrates on the pituitary-hypothalamic axis and the genomic effects of oestrogen, and discusses the current knowledge of each of these factors in determining oestrogen actions in the neuroendocrine system. [source] Protein kinase C-, mediates von Willebrand factor secretion from endothelial cells in response to vascular endothelial growth factor (VEGF) but not histamineJOURNAL OF THROMBOSIS AND HAEMOSTASIS, Issue 11 2008O. LORENZI Summary.,Background:,Vascular endothelial growth factor (VEGF) and histamine induce von Willebrand factor (VWF) release from vascular endothelial cells. Protein kinase C (PKC) is involved in the control of exocytosis in many secretory cell types. Objectives:,We investigated the role of PKC and the interactions between PKC and Ca2+ signaling in both VEGF-induced and histamine-induced VWF secretion from human umbilical vein endothelial cells (HUVECs). Results:,Several PKC inhibitors (staurosporine, Ro31-8220, myristoylated PKC peptide inhibitor and Go6983) block VEGF-induced but not histamine-induced VWF secretion. PKC-, and novel PKCs (PKC-,, PKC-,, and PKC-,), but not PKC-,, are expressed in HUVECs. Both VEGF and histamine activate PKC-,. However, gene inactivation experiments using small interfering RNA indicate that PKC-, (but not PKC-,) is involved in the regulation of VEGF-induced but not histamine-induced secretion. Both VEGF and histamine induce a rise in cytosolic free Ca2+ ([Ca2+]c), but the response to VEGF is weaker and even absent in a significant subset of cells. Furthermore, VEGF-induced secretion is largely preserved when the rise in [Ca2+]c is prevented by BAPTA-AM. Conclusions:,Our study identifies striking agonist specificities in signal,secretion coupling. Histamine-induced secretion is dependent on [Ca2+]c but not PKC, whereas VEGF-induced secretion is largely dependent on PKC-, and significantly less on [Ca2+]c. Our data firmly establish the key role of PKC-, in VEGF-induced VWF release, but suggest that a third, VEGF-specific, signaling intermediate is required as a PKC-, coactivator. [source] Review article: transcriptional events controlling the terminal differentiation of intestinal endocrine cellsALIMENTARY PHARMACOLOGY & THERAPEUTICS, Issue 2000H. Mutoh Summary Secretin-producing enteroendocrine cells arise from a multipotential endocrine progenitor in the crypts of the small intestine. As these cells migrate up the crypt-villus axis, they produce secretin and stop dividing as they terminally differentiate and die. Transcription of the secretin gene is controlled by a complex enhancer binding to multiple transcription factors. The basic helix-loop-helix protein, BETA2, binds to an E box sequence and associates with the p300 coactivator to activate transcription of the secretin gene. Basic helix-loop-helix proteins appear to play a pivotal role in the control of cellular differentiation. BETA2 induces cell cycle arrest and apoptosis in addition to activating secretin gene expression. Thus BETA2 may function as a master regulatory gene to coordinate terminal differentiation of secretin cells. [source] A secreted anti-activator, OspD1, and its chaperone, Spa15, are involved in the control of transcription by the type III secretion apparatus activity in Shigella flexneriMOLECULAR MICROBIOLOGY, Issue 6 2005Claude Parsot Summary Bacteria of Shigella spp. are responsible for shigellosis in humans and use a type III secretion (TTS) system to enter epithelial cells and trigger apoptosis in macrophages. Transit of translocator and effector proteins through the TTS apparatus is activated upon contact of bacteria with host cells. Transcription of ,15 genes encoding effectors is regulated by the TTS apparatus activity and controlled by MxiE, an AraC family activator, and its coactivator IpgC, the chaperone of IpaB and IpaC translocators. Using a genetic screen, we identified ospD1 as a gene whose product negatively controls expression of genes regulated by secretion activity. OspD1 associates with the chaperone Spa15 and the activator MxiE and acts as an anti-activator until it is secreted. The mechanism regulating transcription in response to secretion activity involves an activator (MxiE), an anti-activator (OspD1), a co-anti-activator (Spa15), a coactivator (IpgC) and two anti-coactivators (IpaB and IpaC) whose alternative and mutually exclusive interactions are controlled by the duration of the TTS apparatus activity. [source] Over-expression of putative transcriptional coactivator KELP interferes with Tomato mosaic virus cell-to-cell movementMOLECULAR PLANT PATHOLOGY, Issue 2 2009NOBUMITSU SASAKI SUMMARY Tomato mosaic virus (ToMV) encodes a movement protein (MP) that is necessary for virus cell-to-cell movement. We have demonstrated previously that KELP, a putative transcriptional coactivator of Arabidopsis thaliana, and its orthologue from Brassica campestris can bind to ToMV MP in vitro. In this study, we examined the effects of the transient over-expression of KELP on ToMV infection and the intracellular localization of MP in Nicotiana benthamiana, an experimental host of the virus. In co-bombardment experiments, the over-expression of KELP inhibited virus cell-to-cell movement. The N-terminal half of KELP (KELPdC), which had been shown to bind to MP, was sufficient for inhibition. Furthermore, the over-expression of KELP and KELPdC, both of which were co-localized with ToMV MP, led to a reduction in the plasmodesmal association of MP. In the absence of MP expression, KELP was localized in the nucleus and the cytoplasm by the localization signal in its N-terminal half. It was also shown that ToMV amplified normally in protoplasts prepared from leaf tissue that expressed KELP transiently. These results indicate that over-expressed KELP interacts with MP in vivo and exerts an inhibitory effect on MP function for virus cell-to-cell movement, but not on virus amplification in individual cells. [source] Interaction of expanded polyglutamine stretches with nuclear transcription factors leads to aberrant transcriptional regulation in polyglutamine diseasesNEUROPATHOLOGY, Issue 4 2000Takayoshi Shimohata At least eight inherited neurodegenerative diseases are known to be caused by expanded CAG repeats encoding polyglutamine (polyQ) stretches. Although cytotoxicities of expanded polyQ stretches have been suggested, the molecular mechanisms of neurodegeneration remain unclear. The nuclear translocation of mutant proteins containing expanded polyQ stretches has been demonstrated as a prerequisite for the expression of their cytotoxicity. Hypothesizing that nuclear proteins that interact with mutant proteins, particularly, those that bind to the expanded polyQ stretches, are involved in the pathogenetic mechanisms underlying neurodegeneration, nuclear proteins were screened for their capability of binding to expanded polyQ stretches. It was found that expanded polyQ stretches preferentially bind to TAFII130, a coactivator involved in cAMP-responsive element-binding protein (CREB)-dependent transcriptional activation. The binding of TAFII130 with expanded polyQ stretches strongly suppresses CREB-dependent transcriptional activation, suggesting that interference with transcription due to the binding of expanded polyQ stretches with TAFII130 and redistribution of TAFII130 are involved in the pathogenetic mechanisms underlying neurodegeneration. [source] ERAP75 functions as a coactivator to enhance estrogen receptor , transactivation in prostate stromal cells,THE PROSTATE, Issue 12 2008Ming Chen Abstract BACKGROUND Estrogen receptor , (ER,) has been reported to be expressed and function in the prostate stromal cells, and numerous evidences indicated that the stromal ER, signal pathway plays critical roles in prostate development and cancer. ER, requires distinct coregulators for efficient transcriptional regulation. The goal of this study is to examine physical and functional interaction between ER, and ERAP75 in the context of prostate stromal cells. METHOD Yeast two-hybrid assays were used to screen novel ER, interaction proteins. The interaction between ER, and ERAP75 was confirmed by mammalian two-hybrid, GST pull-down, and co-immunoprecipitation methods. The interaction motif was examined by site-directed mutagenesis. The effect of ERAP75 on ER, transactivation and the expression of ER, target genes were determined by luciferase assay and real-time PCR, respectively. RESULT ER, can interact with the C terminus of ERAP75 via its ligand binding domain both in vivo and in vitro. The conserved LXXLL motif within the C terminus of ERAP75 is required for the interaction between ER, and ERAP75. ERAP75 can enhance ER, transactivation in a dose-dependent manner and up-regulate the expression of the endogenous ER, target gene, stromal-derived factor-1 (SDF-1), in the prostate stromal cells. CONCLUSION ERAP75 functions as a novel coactivator that can modulate ER, function in the prostate stromal cells. The understanding of the mechanism of ER, transactivation in prostate stromal cells could possibly help in the development of new strategies to control or treat prostate cancer by targeting its transactivation protein complex. Prostate 68:1273,1282, 2008. © 2008 Wiley-Liss, Inc. [source] Expression of androgen receptor coactivators in normal and cancer prostate tissues and cultured cell linesTHE PROSTATE, Issue 3 2003C. Mestayer Abstract BACKGROUND In prostate cancer cell lines, androgen receptor (AR) coactivators modulate the transcriptional activity of AR. However, very little is known about their expression in normal prostate tissue and during progression to cancer. METHODS AR and coactivators ARA54, ARA55, ARA70, and SRC1 RNA were analyzed by RT-PCR in normal and tumoral tissues of the same prostate, in prostate cell lines, and after hormonal treatments of prostate epithelial cells. RESULTS AR-coactivators were expressed in normal and tumoral tissues and in cultured prostate cells; only ARA55 expression was decreased in tumoral relative to normal tissue of all seven prostates analyzed. It was not expressed in LNCaP and DU145 cancer cells and low in PNT2 immortalized cells in which all coactivator's expression were down regulated by DHT and up regulated by E2. In addition, coactivator's expression was increased in hyperplastic relative to normal prostate fibroblasts. CONCLUSIONS ARA55 is both an AR coactivator and a focal adhesion protein (Hic-5). Its role in the progression of prostate carcinoma may therefore involve these two different functions. Its decrease in cancer tissue suggests that it plays a different role than that expected, namely, facilitate cell proliferation and therefore mobility and metastasis. Prostate 56: 192,200, 2003. © 2003 Wiley-Liss, Inc. [source] Assessing the permissiveness of transcriptional activator binding sitesBIOPOLYMERS, Issue 7 2008Steven P. Rowe Abstract Both genetic and biochemical data suggest that transcriptional activators with little sequence homology nevertheless function through interaction with a shared group of coactivators. Here we show that a series of peptidomimetic transcriptional activation domains interact under cell-fiee and cellular conditions with the metazoan coactivator CBP despite differences in the positioning and identity of the constituent functional groups. Taken together, these results suggest that a key activator binding site within CBP is permissive, accepting multiple arrangements of hydrophobic functional groups. Further, this permissiveness is also observed with a coactivator from S. cerevisiae. Thus, the design of small molecule mimics of transcriptional activation domains with broad function may be more straightforward than previously envisioned. © 2008 Wiley Periodicals, Inc. Biopolymers 89: 578,581, 2008. This article was originally published online as an accepted preprint. The "Published Online" date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com [source] Molecular Characterization of the NCoA-1,STAT,6 InteractionCHEMBIOCHEM, Issue 8 2008Markus Seitz Abstract Many protein,protein interactions involved in cell signalling, cell adhesion and regulation of transcription are mediated by short ,-helical recognition motifs with the sequence Leu-Xaa-Xaa-Leu-Leu (LXXLL, where Xaa is any amino acid). Originally observed in cofactors that interact with hormone-activated nuclear receptors, LXXLL motifs are now known to occur in many transcription factors, including the STAT family, which transmit signals from activated cytokine receptors at the cell surface to target genes in the nucleus. STAT,6 becomes activated in response to IL-4 and IL-13, which regulate immune and anti-inflammatory responses. Structural studies have revealed how an LXXLL motif located in 2.5 turns of an ,-helical peptide derived from STAT,6 provide contacts through the leucine side chains to the coactivator of transcription, NCoA-1. However, since many protein,protein interactions are mediated by LXXLL motifs, it is important to understand how specificity is achieved in this and other signalling pathways. Here, we show that energetically important contacts between STAT,6 and NCoA-1 are made in residues that flank the LXXLL motif, including the underlined residues in the sequence LLPPTEQDLTKLL. We also demonstrate how the affinity for NCoA-1 of peptides derived from this region of STAT,6 can be significantly improved by optimising knobs-into-holes contacts on the surface of the protein. The results provide important new insights into the origins of binding specificity, and might be of practical value in the design of novel small-molecule inhibitors of this important protein,protein interaction. [source] AMP-activated protein kinase control of fat metabolism in skeletal muscleACTA PHYSIOLOGICA, Issue 1 2009D. M. Thomson Abstract AMP-activated protein kinase (AMPK) has emerged as a key regulator of skeletal muscle fat metabolism. Because abnormalities in skeletal muscle metabolism contribute to a variety of clinical diseases and disorders, understanding AMPK's role in the muscle is important. It was originally shown to stimulate fatty acid (FA) oxidation decades ago, and since then much research has been accomplished describing this role. In this brief review, we summarize much of these data, particularly in relation to changes in FA oxidation that occur during skeletal muscle exercise. Potential roles for AMPK exist in regulating FA transport into the mitochondria via interactions with acetyl-CoA carboxylase, malonyl-CoA decarboxylase, and perhaps FA transporter/CD36 (FAT/CD36). Likewise, AMPK may regulate transport of FAs into the cell through FAT/CD36. AMPK may also regulate capacity for FA oxidation by phosphorylation of transcription factors such as CREB or coactivators such as PGC-1,. [source] The sexually dimorphic expression of L7/SPA, an estrogen receptor coactivator, in zebra finch telencephalonDEVELOPMENTAL NEUROBIOLOGY, Issue 14 2007Kelli A. Duncan Abstract Sex differences in the zebra finch (Taeniopygia guttata) brain are robust and include differences in morphology (song control nuclei in males are significantly larger) and behavior (only males sing courtship songs). In zebra finches, hormonal manipulations during development fail to reverse sex differences in song nuclei size and suggest that the classical model of sexual differentiation is incomplete for birds. Coactivators act to initiate transcriptional activity of steroid receptors, and may help explain why hormonal manipulations alone are not sufficient to demasculinize the male zebra finch brain. The present study investigated the expression and localization of L7/SPA (an estrogen receptor coactivator) mRNA and protein expression across the development of zebra finch song nuclei from males and females collected on P1 (song nuclei not yet formed), P10 (posthatch day 10, song nuclei formed), P30 (30 days posthatch, sexually immature but song nuclei formed and birds learning to sing), and adult birds (older than 65 days and sexually mature). Northern blot analysis showed a significant sex difference in P1 and adult L7/SPA mRNA expression while Western blot analysis also showed enhanced expression in the male brain at all age points. Both in situ hybridization and immunohistochemistry demonstrated that L7/SPA mRNA and protein were located in the song nuclei as well as expressed globally. Elevated coactivator expression may be a possible mechanism controlling the development of male song control nuclei, and coactivators such as L7/SPA may be important regulators of the masculinizing effects of estradiol on brain sexual differentiation. © 2007 Wiley Periodicals, Inc. Develop Neurobiol, 2007. [source] Mechanism for transcriptional synergy between interferon regulatory factor (IRF)-3 and IRF-7 in activation of the interferon-, gene promoterFEBS JOURNAL, Issue 18 2004Hongmei Yang The interferon-, promoter has been studied extensively as a model system for combinatorial transcriptional regulation. In virus-infected cells the transcription factors ATF-2, c-Jun, interferon regulatory factor (IRF)-3, IRF-7 and NF-,B, and the coactivators p300/CBP play critical roles in the activation of this and other promoters. It remains unclear, however, why most other combinations of AP-1, IRF and Rel proteins fail to activate the interferon-, gene. Here we have explored how different IRFs may cooperate with other factors to activate transcription. First we showed in undifferentiated embryonic carcinoma cells that ectopic expression of either IRF-3 or IRF-7, but not IRF-1, was sufficient to allow virus-dependent activation of the interferon-, promoter. Moreover, the activity of IRF-3 and IRF-7 was strongly affected by promoter context, with IRF-7 preferentially being recruited to the natural interferon-, promoter. We fully reconstituted activation of this promoter in insect cells. Maximal synergy required IRF-3 and IRF-7 but not IRF-1, and was strongly dependent on the presence of p300/CBP, even when these coactivators only modestly affected the activity of each factor by itself. These results suggest that specificity in activation of the interferon-, gene depends on a unique promoter context and on the role played by coactivators as architectural factors. [source] Transcriptional activity of interferon regulatory factor (IRF)-3 depends on multiple protein,protein interactionsFEBS JOURNAL, Issue 24 2002Hongmei Yang Virus infection results in the activation of a set of cellular genes involved in host antiviral defense. IRF-3 has been identified as a critical transcription factor in this process. The activation mechanism of IRF-3 is not fully elucidated, yet it involves a conformational change triggered by the virus-dependent phosphorylation of its C-terminus. This conformational change leads to nuclear accumulation, DNA binding and transcriptional transactivation. Here we show that two distinct sets of Ser/Thr residues of IRF-3, on phosphorylation, synergize functionally to achieve maximal activation. Remarkably, we find that activated IRF-3 lacks transcriptional activity, but activates transcription entirely through the recruitment of the p300/CBP coactivators. Moreover, we show that two separate domains of IRF-3 interact with several distinct regions of p300/CBP. Interference with any of these interactions leads to a complete loss of transcriptional activity, suggesting that a bivalent interaction is essential for coactivator recruitment by IRF-3. [source] Molecular mechanism of a cross-talk between oestrogen and growth factor signalling pathwaysGENES TO CELLS, Issue 8 2000Shigeaki Kato Oestrogen (E2) plays significant roles in variety of biological events such as the development and maintenance of female reproductive organs, bone and lipid metabolisms. More recently, from study of knock-out mice deficient in oestrogen receptor (ER) , and ER, it turned out that normal spermatogenesis requires the E2 actions. Furthermore, this female steroid hormone is also well known to be deeply involved in many pathophysiological events such as osteoporosis and cancer development in female reproductive organs. It is particularly well known that most breast cancer is dependent on E2 in its development. Such E2 actions are thought to be mediated through two subtypes of ERs. Growth factors have been shown to synergize in this E2 signalling pathway, although the actual molecular mechanism largely remains unknown. Recently, we found that the MAP kinase activated by growth factors phosphorylates the Ser118 residue of the human ER, A/B domain and this phosphorylation potentiates the N-terminal transactivation function (AF-1) of human ER,, indicating the possible molecular mechanism of a novel cross-talk between E2 and growth factor signalling pathways. More recently, we have identified a coactivator associating with the hER, AF-1 in a MAPK-mediated phosphorylation-dependent manner. In this review, the molecular mechanism of this cross-talk is discussed in terms of the transactivation function of ERs, and their coactivators. [source] Epigenetics of prostate cancer: beyond DNA methylationJOURNAL OF CELLULAR AND MOLECULAR MEDICINE, Issue 1 2006W. A. Schulz Abstract Epigenetic mechanisms permit the stable inheritance of cellular properties without changes in DNA sequence or amount. In prostate carcinoma, epigenetic mechanisms are essential for development and progression, complementing, amplifying and diversifying genetic alterations. DNA hypermethylation affects at least 30 individual genes, while repetitive sequences including retrotransposons and selected genes become hypomethylated. Hypermethylation of several genes occurs in a coordinate manner early in carcinogenesis and can be exploited for cancer detection, whereas hypomethylation and further hypermethylation events are associated with progression. DNA methylation alterations interact with changes in chromatin proteins. Prominent alterations at this level include altered patterns of histone modification, increased expression of the EZH2 polycomb histone methyltransferase, and changes in transcriptional corepressors and coactivators. These changes may make prostate carcinoma particularly susceptible to drugs targeting chromatin and DNA modifications. They relate to crucial alterations in a network of transcription factors comprising ETS family proteins, the androgen receptor, NKX3.1, KLF, and HOXB13 homeobox proteins. This network controls differentiation and proliferation of prostate epithelial cells integrating signals from hormones, growth factors and cell adhesion proteins that are likewise distorted in prostate cancer. As a consequence, prostate carcinoma cells appear to be locked into an aberrant state, characterized by continued proliferation of largely differentiated cells. Accordingly, stem cell characteristics of prostate cancer cells appear to be secondarily acquired. The aberrant differentiation state of prostate carcinoma cells also results in distorted mutual interactions between epithelial and stromal cells in the tumor that promote tumor growth, invasion, and metastasis. [source] | ||||||||||||||||||||||||||||