Nuclear Repressor Element-1 Silencing Transcription Factor Research Articles

Spatiotemporal immunolocalisation of REST in the brain of healthy ageing and Alzheimer's disease rats.

In the brain, REST (Repressor Element-1 Silencing Transcription factor) is a key regulator of neuron cell-specific gene expression. Nuclear translocation of neuronal REST has been shown to be neuroprotective in a healthy ageing context. In contrast, inability to upregulate nuclear REST is thought to leave ageing neurons vulnerable to neurodegenerative stimuli, such as Alzheimer's disease (AD) pathology. Hippocampal and cortical neurons are known to be particularly susceptible to AD-associated neurodegeneration. However, REST expression has not been extensively characterised in the healthy ageing brain. Here, we examined the spatiotemporal immunolocalisation of REST in the brains of healthy ageing wild-type Fischer-344 and transgenic Alzheimer's disease rats (TgF344-AD). Nuclear expression of REST increased from 6months to 18months of age in the hippocampus, frontal cortex and subiculum of wild-type rats, but not in TgF344-AD rats. No changes in REST were measured in more posterior cortical regions or in the thalamus. Interestingly, levels of the presynaptic marker synaptophysin, a known gene target of REST, were lower in CA1 hippocampal neurons of 18-month TgF344-AD rats compared to 18-month wild-types, suggesting that elevated nuclear REST may protect against synapse loss in the CA1 of 18-month wild-type rats. High REST expression in ageing wild-type rats did not, however, protect against axonal loss nor against astroglial reactivity in the hippocampus. Taken together, our data confirm that changes in nuclear REST expression are context-, age- and brain region-specific. Moreover, key brain structures involved in learning and memory display elevated REST expression in healthy ageing wild-type rats but not TgF344-AD rats.

High Aβ load may cause microglial cell dysfunction and reduced nuclear repressor element-1 silencing transcription factor (REST) expression which might be ascribed to its degradation by ubiquitination.

This study aimed to investigate the effects of high Aβ load on the microglial function, neuronal activity, and repressor element-1 silencing transcription factor (REST) expression and nuclear localization and further explore the mechanism underlying nuclear REST deficiency and the correlation between pathology and symptoms in Alzheimer's disease (AD). BV2 cells and N2A cells were treated with Aβ at different concentrations, and the viability, apoptosis and autophagy of these cells were further evaluated. The expression of major histocompatibility complex class II (MHC-II, a marker of microglial activation), REST in the neurons and REST specific phosphorylase casein kinase 1 (CK1) were detected. Aβ at a low concentration (2.5 µmol/L) could alter the microglial morphology, and the proportion of amoebic microglia and protein expression of MHC-II increased in a Aβ concentration dependent manner. Aβ at a high concentration (10 µmol/L) was able to reduce REST expression, elevate the expression of pro-apoptotic and pro-autophagic genes, inhibit the expression of anti-apoptotic gene, and reduce the neuronal activity. REST expression reduced, but CK1 increased in neurons, and CK1 inhibitor significantly increased REST expression. there was co-expression of REST and CK1 in the brain of AD mice, which was characterized by reduced nuclear REST expression and elevated CK1 expression. High Aβ load may cause microglial cell dysfunction and loss of REST expression in the neurons, resulting in dementia. The reduced nuclear REST might be ascribed to its degradation by ubiquitination. This supports the hypothesis that high plaque load may increase the risk for dementia.

Novel Inflammatory Signaling via Interleukin‐13 Decreases Potassium Channel Expression and Increases Vascular Smooth Muscle Excitability

The transcriptional repressor element‐1 (RE1) silencing transcription factor (REST), also known as neuron‐restrictive silencer factor (NRSF) is a gene silencing transcription factor, which has been characterized as a master regulator of the neuronal phenotype. REST plays a key role in the development of the nervous system and is a critical player in the etiology of neurodegenerative diseases such as Huntington's Disease, though little is known about the role of REST in non‐neuronal cells. We are exploring a potential role of REST as a mediator between inflammation and changes in smooth muscle phenotype. Kv7.5 voltage‐dependent potassium channels, encoded by the KCNQ5 gene, are expressed in smooth muscle cells where they play an important role in determining resting membrane potential. Interleukin‐13 (IL‐13) is an inflammatory cytokine, which is implicated as a primary mediator of the phenotypic changes induced by allergic inflammation in many tissues. In the present study, we hypothesized that IL‐13 can increase nuclear REST and decrease KCNQ5 mRNA expression and Kv7.5 protein in vascular smooth muscle cells, providing a potential link between inflammation, REST and potassium channel‐mediated vascular hyper‐responsiveness. In support of this hypothesis, using A7r5 rat aortic smooth muscle cells, we found that 1) IL‐13 treatment significantly increased nuclear REST, and 2) significantly suppressed the expression of KCNQ5 and Kv7.5 currents, resulting in increased sensitivity of A7r5 cells to arginine vasopressin (AVP). 3) REST overexpression also significantly decreased Kv7.5 currents, and 4) significantly increased the sensitivity of A7r5 cells to AVP. We conclude that inflammation that induces IL‐13 may increase nuclear REST levels and thereby decrease KCNQ5 expression and Kv7.5 currents, ultimately increasing vascular smooth muscle cell excitability and contributing to vascular hyper‐responsiveness.Support or Funding InformationThe project described was supported by Award Number I01BX007080 from the Biomedical Laboratory Research & Development Service of the VA Office of Research and Development.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Alternative REST Splicing Underappreciated.

As a major orchestrator of the cellular epigenome, the repressor element-1 silencing transcription factor (REST) can either repress or activate thousands of genes depending on cellular context, suggesting a highly context-dependent REST function tuned by environmental cues. While REST shows cell-type non-selective active transcription (Kojima et al., 2001), an N-terminal REST4 isoform caused by alternative splicing, inclusion of an extra exon (N3c) which introduces a pre-mature stop codon, contributes to neurogenesis and tumorigenesis (Palm et al., 1998, 1999; Lee et al., 2000; Raj et al., 2011). Recently, in line with established epigenetic regulation of pre-mRNA splicing (Allo et al., 2010; Luco et al., 2011), we demonstrated that REST undergoes extensive, context-dependent alternative splicing which results in the formation of a large number of mRNA variants predictive of multiple protein isoforms (Chen and Miller, 2013). Supported by the fact that immunoblotting/-staining with different anti-REST antibodies yield different results, alternative splicing allows production of various structurally and functionally different REST protein isoforms in response to shifting physiologic requirements, shedding light on environmental regulation of REST function. However, REST isoforms might be differentially assayed or manipulated, leading to data misinterpretation and controversial findings. For example, in contrast to the proposed neurotoxicity of elevated nuclear REST in ischemia (Noh et al., 2012) and Huntington’s disease (Zuccato et al., 2003; Buckley et al., 2010), Lu et al. recently reported decreased nuclear REST in Alzheimer’s disease and neuroprotection of REST in aging brain (Lu et al., 2014). Unfortunately, alternative REST splicing was largely neglected by Lu et al. (2014), making it necessary for a reevaluation of their findings. As shown in Figure 1 A , human REST gene boundary is now doubled by an alternative …

Lithium alleviates neurotoxic prion peptide-induced synaptic damage and neuronal death partially by the upregulation of nuclear target REST and the restoration of Wnt signaling

Prion diseases are a group of infectious neurodegenerative diseases characterized by multiple neuropathological hallmarks, including accumulation of PrPSc, synaptic damage, and neuronal death. We previously reported that the repressor element 1-silencing transcription factor (REST), a novel neuroprotective marker in neurodegeneration, protects neurons against neurotoxic peptide (PrP106-126)-induced neurotoxicity, but fails to maintain survival following prolonged exposure to PrP106-126. Because Wnt signaling partially induces REST and is activated by lithium, we investigated the effects of lithium on REST in prion diseases. Lithium restores nuclear expression of REST, which is essential for regulating survival proteins. Lithium also mimics neuroprotective functions when REST is blocked, and these beneficial effects are additive with REST overexpression under physiological conditions. Reciprocally, under PrP106-126-stimulated pathological conditions, REST plays a critical role in the neuroprotective mechanisms of lithium treatment. Although lithium recovers Wnt signaling by inhibiting glycogen synthase kinase-3β and stabilizing β-catenin, restores survival associated proteins after exposure to PrP106-126 in primary cortical neurons. Knockdown of REST significantly suppresses the neuroprotective function of lithium. Conversely, overexpression of REST partially recovers its actions. Notably, lithium directly alleviates PrP106-126-induced synaptic damage and neuronal cell death by preventing changes in presynaptic and postsynaptic marker proteins and promoting survival pathways also partially via the expression of REST. Our results suggest that REST acts as a novel and important nuclear target for lithium. We hypothesize that PrP106-126-stimulated neurotoxicity induces Wnt signaling dysfunction and lithium mimics this signaling cascade, suggesting that lithium should be considered as a potential therapeutic agent against prion diseases.

Modulation of nuclear REST by alternative splicing: a potential therapeutic target for Huntington's disease.

Huntington's disease (HD) is caused by a genetically mutated huntingtin (mHtt) protein with expanded polyQ stretch, which impairs cytosolic sequestration of the repressor element‐1 silencing transcription factor (REST), resulting in excessive nuclear REST and subsequent repression of neuronal genes. We recently demonstrated that REST undergoes extensive, context‐dependent alternative splicing, of which exon‐3 skipping (∆E3)—a common event in human and nonhuman primates—causes loss of a motif critical for REST nuclear targeting. This study aimed to determine whether ∆E3 can be targeted to reduce nuclear REST and rescue neuronal gene expression in mouse striatal‐derived, mHtt‐expressing STHdhQ111/Q111 cells—a well‐established cellular model of HD. We designed two morpholino antisense oligos (ASOs) targeting the splice sites of Rest E3 and examined their effects on ∆E3, nuclear Rest accumulation and Rest‐controlled gene expression in STHdhQ111/Q111 cells. We found that (1) the ASOs treatment significantly induced ∆E3, reduced nuclear Rest, and rescued transcription and/or mis‐splicing of specific neuronal genes (e.g. Syn1 and Stmn2) in STHdhQ111/Q111 cells; and (2) the ASOs‐induced transcriptional regulation was dependent on ∆E3 induction and mimicked by siRNA‐mediated knock‐down of Rest expression. Our findings demonstrate modulation of nuclear REST by ∆E3 and its potential as a new therapeutic target for HD and provide new insights into environmental regulation of genome function and pathogenesis of HD. As ∆E3 is modulated by cellular signalling and linked to various types of cancer, we anticipate that ∆E3 contributes to environmentally tuned REST function and may have a broad range of clinical implications.

Low Oxygen Modulates Multiple Signaling Pathways, Increasing Self-Renewal, While Decreasing Differentiation, Senescence, and Apoptosis in Stromal MIAMI Cells.

Human bone marrow multipotent mesenchymal stromal cell (hMSC) number decreases with aging. Subpopulations of hMSCs can differentiate into cells found in bone, vasculature, cartilage, gut, and other tissues and participate in their repair. Maintaining throughout adult life such cell subpopulations should help prevent or delay the onset of age-related degenerative conditions. Low oxygen tension, the physiological environment in progenitor cell-rich regions of the bone marrow microarchitecture, stimulates the self-renewal of marrow-isolated adult multilineage inducible (MIAMI) cells and expression of Sox2, Nanog, Oct4a nuclear accumulation, Notch intracellular domain, notch target genes, neuronal transcriptional repressor element 1 (RE1)-silencing transcription factor (REST), and hypoxia-inducible factor-1 alpha (HIF-1α), and additionally, by decreasing the expression of (i) the proapoptotic proteins, apoptosis-inducing factor (AIF) and Bak, and (ii) senescence-associated p53 expression and β-galactosidase activity. Furthermore, low oxygen increases canonical Wnt pathway signaling coreceptor Lrp5 expression, and PI3K/Akt pathway activation. Lrp5 inhibition decreases self-renewal marker Sox2 mRNA, Oct4a nuclear accumulation, and cell numbers. Wortmannin-mediated PI3K/Akt pathway inhibition leads to increased osteoblastic differentiation at both low and high oxygen tension. We demonstrate that low oxygen stimulates a complex signaling network involving PI3K/Akt, Notch, and canonical Wnt pathways, which mediate the observed increase in nuclear Oct4a and REST, with simultaneous decrease in p53, AIF, and Bak. Collectively, these pathway activations contribute to increased self-renewal with concomitant decreased differentiation, cell cycle arrest, apoptosis, and/or senescence in MIAMI cells. Importantly, the PI3K/Akt pathway plays a central mechanistic role in the oxygen tension-regulated self-renewal versus osteoblastic differentiation of progenitor cells.

Dysregulation of REST‐regulated coding and non‐coding RNAs in a cellular model of Huntington's disease

Huntingtin (Htt) protein interacts with many transcriptional regulators, with widespread disruption to the transcriptome in Huntington's disease (HD) brought about by altered interactions with the mutant Htt (muHtt) protein. Repressor Element-1 Silencing Transcription Factor (REST) is a repressor whose association with Htt in the cytoplasm is disrupted in HD, leading to increased nuclear REST and concomitant repression of several neuronal-specific genes, including brain-derived neurotrophic factor (Bdnf). Here, we explored a wide set of HD dysregulated genes to identify direct REST targets whose expression is altered in a cellular model of HD but that can be rescued by knock-down of REST activity. We found many direct REST target genes encoding proteins important for nervous system development, including a cohort involved in synaptic transmission, at least two of which can be rescued at the protein level by REST knock-down. We also identified several microRNAs (miRNAs) whose aberrant repression is directly mediated by REST, including miR-137, which has not previously been shown to be a direct REST target in mouse. These data provide evidence of the contribution of inappropriate REST-mediated transcriptional repression to the widespread changes in coding and non-coding gene expression in a cellular model of HD that may affect normal neuronal function and survival.

Transformation by E1A Oncoprotein Involves Ubiquitin-Mediated Proteolysis of the Neuronal and Tumor Repressor REST in the Nucleus

The adenovirus early region 1A (E1A) protein promotes cell immortalization and transformation by mediating the activities of key cellular regulators. The repressor element 1-silencing transcription factor (REST), which is a major neuronal and tumor suppressor, was previously found mainly in the cytoplasm rather than in the nuclei of adenovirus-transformed rodent cells (22). We now demonstrate that the loss of REST in the nucleus is due to its rapid degradation by the ubiquitin-proteasome system. Only nuclear REST, but not its cytoplasmic counterpart, was ubiquitinated and degraded. REST degradation was blocked by the ubiquitination inhibitor PYR-41 and the proteasome inhibitor MG-132 but not by the nuclear export inhibitor leptomycin B. REST degradation required both of its two C-terminal degrons that are recognized by the ubiquitin ligase SCF(β-TrCP), since deletion or mutation of either degron eliminated degradation. Importantly, E1A was shown to mediate REST ubiquitination and degradation by upregulating β-TrCP. Knockdown of E1A in virus-transformed cells reduced both β-TrCP and ubiquitination of nuclear REST. In contrast, when expressed in HeLa cells, E1A enhanced the degradation of nuclear REST. Reconstitution of REST in virus-transformed cells negatively affected E1A-mediated cell proliferation and anchorage-independent growth. These data strongly indicate that E1A stimulates ubiquitination and proteolysis of REST in the nucleus, thereby abolishing the tumor suppressor functions of REST.

Rescue of gene expression by modified REST decoy oligonucleotides in a cellular model of Huntington’s disease

Transcriptional dysfunction is a prominent hallmark of Huntington's disease (HD). Several transcription factors have been implicated in the aetiology of HD progression and one of the most prominent is repressor element 1 (RE1) silencing transcription factor (REST). REST is a global repressor of neuronal gene expression and in the presence of mutant Huntingtin increased nuclear REST levels lead to elevated RE1 occupancy and a concomitant increase in target gene repression, including brain-derived neurotrophic factor. It is of great interest to devise strategies to reverse transcriptional dysregulation caused by increased nuclear REST and determine the consequences in HD. Thus far, such strategies have involved RNAi or mutant REST constructs. Decoys are double-stranded oligodeoxynucleotides corresponding to the DNA-binding element of a transcription factor and act to sequester it, thereby abrogating its transcriptional activity. Here, we report the use of a novel decoy strategy to rescue REST target gene expression in a cellular model of HD. We show that delivery of the decoy in cells expressing mutant Huntingtin leads to its specific interaction with REST, a reduction in REST occupancy of RE1s and rescue of target gene expression, including Bdnf. These data point to an alternative strategy for rebalancing the transcriptional dysregulation in HD.

Nontelomeric TRF2-REST Interaction Modulates Neuronal Gene Silencing and Fate of Tumor and Stem Cells

Removal of TRF2, a telomere shelterin protein, recapitulates key aspects of telomere attrition including the DNA-damage response and cell-cycle arrest [1]. Distinct from the response of proliferating cells to loss of TRF2 [2, 3], in rodent noncycling cells, TRF2 inhibition promotes differentiation and growth [4, 5]. However, the mechanism that couples telomere gene-silencing features [6-8] to differentiation programs has yet to be elucidated. Here we describe an extratelomeric function of TRF2 in the regulation of neuronal genes mediated by the interaction of TRF2 with repressor element 1-silencing transcription factor (REST), a master repressor of gene networks devoted to neuronal functions [9-12]. TRF2-REST complexes are readily detected by coimmunoprecipitation assays and are localized to aggregated PML-nuclear bodies in undifferentiated pluripotent human NTera2 stem cells. Inhibition of TRF2, either by a dominant-negative mutant or by RNA interference, dissociates TRF2-REST complexes resulting in ubiquitin-proteasomal degradation of REST. Consequentially, REST-targeted neural genes (L1CAM, beta3-tubulin, synaptophysin, and others) are derepressed, resulting in acquisition of neuronal phenotypes. Notably, selective damage to telomeres without affecting TRF2 levels causes neither REST degradation nor cell differentiation. Thus, in addition to protecting telomeres, TRF2 possesses a novel role in stabilization of REST thereby controlling neural tumor and stem cell fate.