A novel peptide derived from vascular endothelial growth factor prevents amyloid beta aggregation and toxicity

Amyloid-β oligomers (Aβo) are the most pathologically relevant Aβ species in Alzheimer's disease (AD), because they induce early synaptic dysfunction that leads to learning and memory impairments. In contrast, increasing VEGF (Vascular Endothelial Growth Factor) brain levels have been shown to improve learning and memory processes, and to alleviate Aβ-mediated synapse dysfunction. Here, we designed a new peptide, the blocking peptide (BP), which is derived from an Aβo-targeted domain of the VEGF protein, and investigated its effect on Aβ-associated toxicity. Using a combination of biochemical, 3D and ultrastructural imaging, and electrophysiological approaches, we demonstrated that BP strongly interacts with Aβo and blocks Aβ fibrillar aggregation process, leading to the formation of Aβ amorphous aggregates. BP further impedes the formation of structured Aβo and prevents their pathogenic binding to synapses. Importantly, acute BP treatment successfully rescues long-term potentiation (LTP) in the APP/PS1 mouse model of AD, at an age when LTP is highly impaired in hippocampal slices. Moreover, BP is also able to block the interaction between Aβo and VEGF, which suggests a dual mechanism aimed at both trapping Aβo and releasing VEGF to alleviate Aβo-induced synaptic damage. Our findings provide evidence for a neutralizing effect of the BP on Aβ aggregation process and pathogenic action, highlighting a potential new therapeutic strategy.

Correction: Ponzo et al. Nucleolin Therapeutic Targeting Decreases Pancreatic Cancer Immunosuppression. Cancers 2022, 14, 4265

In the original publication [...].

Fluorescent Polymer-AS1411-Aptamer Probe for dSTORM Super-Resolution Imaging of Endogenous Nucleolin

Nucleolin is a multifunctional protein involved in essential biological processes. To precisely localize it and unravel its different roles in cells, fluorescence imaging is a powerful tool, especially super-resolution techniques. Here, we developed polymer-aptamer probes, both small and bright, adapted to direct stochastic optical reconstruction microscopy (dSTORM). Well-defined fluorescent polymer chains bearing fluorophores (AlexaFluor647) and a reactive end group were prepared via RAFT polymerization. The reactive end-group was then used for the oriented conjugation with AS1411, a DNA aptamer that recognizes nucleolin with high affinity. Conjugation via strain-promoted alkyne/azide click chemistry (SPAAC) between dibenzylcyclooctyne-ended fluorescent polymer chains and 3'-azido-functionalized nucleic acids proved to be the most efficient approach. In vitro and in cellulo evaluations demonstrated that selective recognition for nucleolin was retained. Their brightness and small size make these polymer-aptamer probes an appealing alternative to immunofluorescence, especially for super-resolution (10-20 nm) nanoscopy. dSTORM imaging demonstrated the ability of our fluorescent polymer-aptamer probe to provide selective and super-resolved detection of cell surface nucleolin.

Alteration of ribosome function upon 5-fluorouracil treatment favors cancer cell drug-tolerance

Mechanisms of drug-tolerance remain poorly understood and have been linked to genomic but also to non-genomic processes. 5-fluorouracil (5-FU), the most widely used chemotherapy in oncology is associated with resistance. While prescribed as an inhibitor of DNA replication, 5-FU alters all RNA pathways. Here, we show that 5-FU treatment leads to the production of fluorinated ribosomes exhibiting altered translational activities. 5-FU is incorporated into ribosomal RNAs of mature ribosomes in cancer cell lines, colorectal xenografts, and human tumors. Fluorinated ribosomes appear to be functional, yet, they display a selective translational activity towards mRNAs depending on the nature of their 5'-untranslated region. As a result, we find that sustained translation of IGF-1R mRNA, which encodes one of the most potent cell survival effectors, promotes the survival of 5-FU-treated colorectal cancer cells. Altogether, our results demonstrate that "man-made" fluorinated ribosomes favor the drug-tolerant cellular phenotype by promoting translation of survival genes.

Nucleolin Aptamer N6L Reprograms the Translational Machinery and Acts Synergistically with mTORi to Inhibit Pancreatic Cancer Proliferation

Simple Summary

Pancreatic cancer is an aggressive disease characterized by its invasiveness, rapid progression, and resistance to conventional therapy. There is a need to identify new molecules to improve current therapies. The aim of this study was to analyze how the pancreatic cancer cells react to the treatment with an inhibitor of nucleolin, N6L. To this end, we analyzed how the translation was affected in the cells during the treatment. We discovered that in response to N6L, a signaling pathway called the mTOR pathway was activated and was involved in the activation of translation of a subset of mRNA that could be involved in the resistance of the cells to the treatment. Indeed, we showed that the combined action of inhibitors of the mTOR pathway with N6L synergistically inhibited the cancer cells’ proliferation. We propose that this new combination of molecules could be a novel therapeutic option for pancreatic cancer.

Abstract

We previously showed that N6L, a pseudopeptide that targets nucleolin, impairs pancreatic ductal adenocarcinoma (PDAC) growth and normalizes tumor vessels in animal models. In this study, we analyzed the translatome of PDAC cells treated with N6L to identify the pathways that were either repressed or activated. We observed a strong decrease in global protein synthesis. However, about 6% of the mRNAs were enriched in the polysomes. We identified a 5′TOP motif in many of these mRNAs and demonstrated that a chimeric RNA bearing a 5‘TOP motif was up-regulated by N6L. We demonstrated that N6L activates the mTOR pathway, which is required for the translation of these mRNAs. An inhibitory synergistic effect in PDAC cell lines, including patient-derived xenografts and tumor-derived organoids, was observed when N6L was combined with mTOR inhibitors. In conclusion, N6L reduces pancreatic cells proliferation, which then undergoes translational reprogramming through activation of the mTOR pathway. N6L and mTOR inhibitors act synergistically to inhibit the proliferation of PDAC and human PDX cell lines. This combotherapy of N6L and mTOR inhibitors could constitute a promising alternative to treat pancreatic cancer.

A novel view on an old drug, 5-fluorouracil: an unexpected RNA modifier with intriguing impact on cancer cell fate

5-Fluorouracil (5-FU) is a chemotherapeutic drug widely used to treat patients with solid tumours, such as colorectal and pancreatic cancers. Colorectal cancer (CRC) is the second leading cause of cancer-related death and half of patients experience tumour recurrence. Used for over 60 years, 5-FU was long thought to exert its cytotoxic effects by altering DNA metabolism. However, 5-FU mode of action is more complex than previously anticipated since 5-FU is an extrinsic source of RNA modifications through its ability to be incorporated into most classes of RNA. In particular, a recent report highlighted that, by its integration into the most abundant RNA, namely ribosomal RNA (rRNA), 5-FU creates fluorinated active ribosomes and induces translational reprogramming. Here, we review the historical knowledge of 5-FU mode of action and discuss progress in the field of 5-FU-induced RNA modifications. The case of rRNA, the essential component of ribosome and translational activity, and the plasticity of which was recently associated with cancer, is highlighted. We propose that translational reprogramming, induced by 5-FU integration in ribosomes, contributes to 5-FU-driven cell plasticity and ultimately to relapse.

Nucleolin Targeting by N6L Inhibits Wnt/β-Catenin Pathway Activation in Pancreatic Ductal Adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is a highly aggressive and resistant cancer with no available effective therapy. We have previously demonstrated that nucleolin targeting by N6L impairs tumor growth and normalizes tumor vessels in PDAC mouse models. Here, we investigated new pathways that are regulated by nucleolin in PDAC. We found that N6L and nucleolin interact with β-catenin. We found that the Wnt/β-catenin pathway is activated in PDAC and is necessary for tumor-derived 3D growth. N6L and nucleolin loss of function induced by siRNA inhibited Wnt pathway activation by preventing β-catenin stabilization in PDAC cells. N6L also inhibited the growth and the activation of the Wnt/β-catenin pathway in vivo in mice and in 3D cultures derived from MIA PaCa2 tumors. On the other hand, nucleolin overexpression increased β-catenin stabilization. In conclusion, in this study, we identified β-catenin as a new nucleolin interactor and suggest that the Wnt/β-catenin pathway could be a new target of the nucleolin antagonist N6L in PDAC.

Chromatin Protein PC4 Orchestrates B Cell Differentiation by Collaborating with IKAROS and IRF4

The chromatin protein positive coactivator 4 (PC4) has multiple functions, including chromatin compaction. However, its role in immune cells is largely unknown. We show that PC4 orchestrates chromatin structure and gene expression in mature B cells. B-cell-specific PC4-deficient mice show impaired production of antibody upon antigen stimulation. The PC4 complex purified from B cells contains the transcription factors (TFs) IKAROS and IRF4. IKAROS protein is reduced in PC4-deficient mature B cells, resulting in de-repression of their target genes in part by diminished interactions with gene-silencing components. Upon activation, the amount of IRF4 protein is not increased in PC4-deficient B cells, resulting in reduction of plasma cells. Importantly, IRF4 reciprocally induces PC4 expression via a super-enhancer. PC4 knockdown in human B cell lymphoma and myeloma cells reduces IKAROS protein as an anticancer drug, lenalidomide. Our findings establish PC4 as a chromatin regulator of B cells and a possible therapeutic target adjoining IKAROS in B cell malignancies.

Ribosome Biogenesis Alterations in Colorectal Cancer

Many studies have focused on understanding the regulation and functions of aberrant protein synthesis in colorectal cancer (CRC), leaving the ribosome, its main effector, relatively underappreciated in CRC. The production of functional ribosomes is initiated in the nucleolus, requires coordinated ribosomal RNA (rRNA) processing and ribosomal protein (RP) assembly, and is frequently hyperactivated to support the needs in protein synthesis essential to withstand unremitting cancer cell growth. This elevated ribosome production in cancer cells includes a strong alteration of ribosome biogenesis homeostasis that represents one of the hallmarks of cancer cells. None of the ribosome production steps escape this cancer-specific dysregulation. This review summarizes the early and late steps of ribosome biogenesis dysregulations described in CRC cell lines, intestinal organoids, CRC stem cells and mouse models, and their possible clinical implications. We highlight how this cancer-related ribosome biogenesis, both at quantitative and qualitative levels, can lead to the synthesis of ribosomes favoring the translation of mRNAs encoding hyperproliferative and survival factors. We also discuss whether cancer-related ribosome biogenesis is a mere consequence of cancer progression or is a causal factor in CRC, and how altered ribosome biogenesis pathways can represent effective targets to kill CRC cells. The association between exacerbated CRC cell growth and alteration of specific steps of ribosome biogenesis is highlighted as a key driver of tumorigenesis, providing promising perspectives for the implementation of predictive biomarkers and the development of new therapeutic drugs.

In Cellulo Evaluation of the Therapeutic Potential of NHC Platinum Compounds in Metastatic Cutaneous Melanoma

We describe here the evaluation of the cytotoxic efficacy of two platinum (II) complexes bearing an N-heterocyclic carbene (NHC) ligand, a pyridine ligand and bromide or iodide ligands on a panel of human metastatic cutaneous melanoma cell lines representing different genetic subsets including BRAF-inhibitor-resistant cell lines, namely A375, SK-MEL-28, MeWo, HMCB, A375-R, SK-MEL-5-R and 501MEL-R. Cisplatin and dacarbazine were also studied for comparison purposes. Remarkably, the iodine-labelled Pt-NHC complex strongly inhibited proliferation of all tested melanoma cells after 1-h exposure, likely due to its rapid uptake by melanoma cells. The mechanism of this inhibitory activity involves the formation of DNA double-strand breaks and apoptosis. Considering the intrinsic chemoresistance of metastatic melanoma cells of current systemic treatments, these findings are promising and could give research opportunities in the future to improve the prognosis of patients suffering from unresectable metastatic melanoma that are not eligible or that do not respond to the most effective drugs available to date, namely BRAF inhibitors and the anti-PD-1 monoclonal antibody (mAb).

AS1411-conjugated gold nanoparticles affect cell proliferation through a mechanism that seems independent of nucleolin

G-rich oligonucleotide, AS1411, has been shown to interact with nucleolin and to inhibit cancer cell proliferation and tumor growth. This antiproliferative action is increased when AS1411 is conjugated to different types of nanoparticles. However, the molecular mechanisms are not known. In this work, we show in several cell lines that optimized AS1411-conjugated gold nanoparticles (GNS-AS1411) inhibit nucleolin expression at the RNA and protein levels. We observed an alteration of the nucleolar structure with a decrease of ribosomal RNA accumulation comparable to what is observed upon nucleolin knock down. However, the expression of genes involved in cell cycle and the cell cycle blockage by GNS-AS1411 are not regulated in the same way as that in cells where nucleolin has been knocked down. These data suggest that the anti-proliferative activity of GNS-AS1411 is not the only consequence of nucleolin targeting and down-regulation.

Druggable Nucleolin Identifies Breast Tumours Associated with Poor Prognosis That Exhibit Different Biological Processes

Background: Nucleolin (NCL) is a multifunctional protein with oncogenic properties. Anti-NCL drugs show strong cytotoxic effects, including in triple-negative breast cancer (TNBC) models, and are currently being evaluated in phase II clinical trials. However, few studies have investigated the clinical value of NCL and whether NCL stratified cancer patients. Here, we have investigated for the first time the association of NCL with clinical characteristics in breast cancers independently of the different subtypes. Methods: Using two independent series (n = 216; n = 661), we evaluated the prognostic value of NCL in non-metastatic breast cancers using univariate and/or multivariate Cox-regression analyses. Results: We reported that NCL mRNA expression levels are markers of poor survivals independently of tumour size and lymph node invasion status (n = 216). In addition, an association of NCL expression levels with poor survival was observed in TNBC (n = 40, overall survival (OS) p = 0.0287, disease-free survival (DFS) p = 0.0194). Transcriptomic analyses issued from The Cancer Genome Atlas (TCGA) database (n = 661) revealed that breast tumours expressing either low or high NCL mRNA expression levels exhibit different gene expression profiles. These data suggest that tumours expressing high NCL mRNA levels are different from those expressing low NCL mRNA levels. Conclusions: NCL is an independent marker of prognosis in breast cancers. We anticipated that anti-NCL is a promising therapeutic strategy that could rapidly be evaluated in high NCL-expressing tumours to improve breast cancer management.

Correction: Energy-dependent nucleolar localization of p53 in vitro requires two discrete regions within the p53 carboxyl terminus

Following the publication of this article the authors noted that two images were duplicated in Figure 2B. The corrected figure 2B is below. The authors wish to apologize for any inconvenience caused.

Labeling of native proteins with fluorescent RAFT polymer probes: application to the detection of a cell surface protein using flow cytometry

Fluorescent RAFT polymer probes with an activated ester reactive end-group can be advantageously used to label native proteins.

MacroH2A1.1 regulates mitochondrial respiration by limiting nuclear NAD+ consumption

Histone variants are structural components of eukaryotic chromatin that can replace replication-coupled histones in the nucleosome. The histone variant macroH2A1.1 contains a macrodomain capable of binding NAD+-derived metabolites. Here we report that macroH2A1.1 is rapidly induced during myogenic differentiation through a switch in alternative splicing, and that myotubes that lack macroH2A1.1 have a defect in mitochondrial respiratory capacity. We found that the metabolite-binding macrodomain was essential for sustained optimal mitochondrial function but dispensable for gene regulation. Through direct binding, macroH2A1.1 inhibits basal poly-ADP ribose polymerase 1 (PARP-1) activity and thus reduces nuclear NAD+ consumption. The resultant accumulation of the NAD+ precursor NMN allows for maintenance of mitochondrial NAD+ pools that are critical for respiration. Our data indicate that macroH2A1.1-containing chromatin regulates mitochondrial respiration by limiting nuclear NAD+ consumption and establishing a buffer of NAD+ precursors in differentiated cells.

Multifaceted Nucleolin Protein and Its Molecular Partners in Oncogenesis

Discovered in 1973, nucleolin is one of the most abundant phosphoproteins of the nucleolus. The ability of nucleolin to be involved in many cellular processes is probably related to its structural organization and its capability to form many different interactions with other proteins. Many functions of nucleolin affect cellular processes involved in oncogenesis-for instance: in ribosome biogenesis; in DNA repair, remodeling, and genome stability; in cell division and cell survival; in chemokine and growth factor signaling pathways; in angiogenesis and lymphangiogenesis; in epithelial-mesenchymal transition; and in stemness. In this review, we will describe the different functions of nucleolin in oncogenesis through its interaction with other proteins.

Carbon Dots-AS1411 Aptamer Nanoconjugate for Ultrasensitive Spectrofluorometric Detection of Cancer Cells

In the present study, a sensitive and selective signal-on method for aptamer based spectrofluorometric detection of cancer cells is introduced. AS1411, a nucleolin aptamer, is wrapped around water-soluble carbon dots and used as a probe for the detection of several types of cancer cells. Nucleolin, is overexpressed on the surface of cancer cells. Mouse breast 4T1, human breast MCF7, and human cervical HeLa cancer cells were selected as target cells, while human foreskin fibroblast cells HFFF-PI6 served as control cells. For the sensitive and selective spectrofluorimetric detection of target cancer cells in the presence of control cells, the cells were incubated in carbon dots-aptamer solutions, the cell suspensions were subsequently centrifuged and the fluorescence intensities were measured as an analytical signal. The specific targeting of cancer cells by AS1411 aptamers causes the release of carbon dots and enhances the fluorescence intensity. A calibration curve with a dynamic range between 10–4500 4T1 cells and detectability of roughly 7 cells was obtained. In addition, no significant change in the signal was detected by modifying the amount of human foreskin fibroblast control cells. Our results demonstrate similar responses to human MCF7 breast and cervical HeLa cancer cells.

Integrated analysis of mRNA and miRNA expression in HeLa cells expressing low levels of Nucleolin

Nucleolin is an essential protein that plays important roles in the regulation of cell cycle and cell proliferation. Its expression is up regulated in many cancer cells but its molecular functions are not well characterized. Nucleolin is present in the nucleus where it regulates gene expression at the transcriptional and post-transcriptional levels. Using HeLa cells depleted in nucleolin we performed an mRNA and miRNA transcriptomics analysis to identify biological pathways involving nucleolin. Bioinformatic analysis strongly points to a role of nucleolin in lipid metabolism, and in many signaling pathways. Down regulation of nucleolin is associated with lower level of cholesterol while the amount of fatty acids is increased. This could be explained by the decreased and mis-localized expression of the transcription factor SREBP1 and the down-regulation of enzymes involved in the beta-oxidation and degradation of fatty acids. Functional classification of the miRNA-mRNA target genes revealed that deregulated miRNAs target genes involved in apoptosis, proliferation and signaling pathways. Several of these deregulated miRNAs have been shown to control lipid metabolism. This integrated transcriptomic analysis uncovers new unexpected roles for nucleolin in metabolic regulation and signaling pathways paving the way to better understand the global function of nucleolin within the cell.

MacroH2A histone variants maintain nuclear organization and heterochromatin architecture

Genetic loss-of-function studies on development, cancer and somatic cell reprogramming have suggested that the group of macroH2A histone variants might function through stabilizing the differentiated state by a yet unknown mechanism. Here, we present results demonstrating that macroH2A variants have a major function in maintaining nuclear organization and heterochromatin architecture. Specifically, we find that a substantial amount of macroH2A is associated with heterochromatic repeat sequences. We further identify macroH2A on sites of interstitial heterochromatin decorated by histone H3 trimethylated on K9 (H3K9me3). Loss of macroH2A leads to major defects in nuclear organization, including reduced nuclear circularity, disruption of nucleoli and a global loss of dense heterochromatin. Domains formed by DNA repeat sequences are disorganized, expanded and fragmented, and mildly re-expressed when depleted of macroH2A. At the molecular level, we find that macroH2A is required for the interaction of repeat sequences with the nucleostructural protein lamin B1. Taken together, our results argue that a major function of macroH2A histone variants is to link nucleosome composition to higher-order chromatin architecture.

Acidic domains differentially read histone H3 lysine 4 methylation status and are widely present in chromatin-associated proteins

Histone methylation is believed to provide binding sites for specific reader proteins, which translate histone code into biological function. Here we show that a family of acidic domain-containing proteins including nucleophosmin (NPM1), pp32, SET/TAF1β, nucleolin (NCL) and upstream binding factor (UBF) are novel H3K4me2-binding proteins. These proteins exhibit a unique pattern of interaction with methylated H3K4, as their binding is stimulated by H3K4me2 and inhibited by H3K4me1 and H3K4me3. These proteins contain one or more acidic domains consisting mainly of aspartic and/or glutamic residues that are necessary for preferential binding of H3K4me2. Furthermore, we demonstrate that the acidic domain with sufficient length alone is capable of binding H3K4me2 in vitro and in vivo. NPM1, NCL and UBF require their acidic domains for association with and transcriptional activation of rDNA genes. Interestingly, by defining acidic domain as a sequence with at least 20 acidic residues in 50 continuous amino acids, we identified 655 acidic domain-containing protein coding genes in the human genome and Gene Ontology (GO) analysis showed that many of the acidic domain proteins have chromatin-related functions. Our data suggest that acidic domain is a novel histone binding motif that can differentially read the status of H3K4 methylation and is broadly present in chromatin-associated proteins.

Expression Profiling of Ribosome Biogenesis Factors Reveals Nucleolin as a Novel Potential Marker to Predict Outcome in AML Patients

Acute myeloid leukemia (AML) is a heterogeneous disease. Prognosis is mainly influenced by patient age at diagnosis and cytogenetic alterations, two of the main factors currently used in AML patient risk stratification. However, additional criteria are required to improve the current risk classification and better adapt patient care. In neoplastic cells, ribosome biogenesis is increased to sustain the high proliferation rate and ribosome composition is altered to modulate specific gene expression driving tumorigenesis. Here, we investigated the usage of ribosome biogenesis factors as clinical markers in adult patients with AML. We showed that nucleoli, the nucleus compartments where ribosome production takes place, are modified in AML by analyzing a panel of AML and healthy donor cells using immunofluorescence staining. Using four AML series, including the TCGA dataset, altogether representing a total of about 270 samples, we showed that not all factors involved in ribosome biogenesis have clinical values although ribosome biogenesis is increased in AML. Interestingly, we identified the regulator of ribosome production nucleolin (NCL) as over-expressed in AML blasts. Moreover, we found in two series that high NCL mRNA expression level was associated with a poor overall survival, particular in elderly patients. Multivariate analyses taking into account age and cytogenetic risk indicated that NCL expression in blast cells is an independent marker of reduced survival. Our study identifies NCL as a potential novel prognostic factor in AML. Altogether, our results suggest that the ribosome biogenesis pathway may be of interest as clinical markers in AML.

Nucleolin Targeting Impairs the Progression of Pancreatic Cancer and Promotes the Normalization of Tumor Vasculature

Pancreatic cancer is a highly aggressive tumor, mostly resistant to the standard treatments. Nucleolin is overexpressed in cancers and its inhibition impairs tumor growth. Herein, we showed that nucleolin was overexpressed in human specimens of pancreatic ductal adenocarcinoma (PDAC) and that the overall survival significantly increased in patients with low levels of nucleolin. The nucleolin antagonist N6L strongly impaired the growth of primary tumors and liver metastasis in an orthotopic mouse model of PDAC (mPDAC). Similar antitumor effect of N6L has been observed in a highly angiogenic mouse model of pancreatic neuroendocrine tumor RIP-Tag2. N6L significantly inhibited both human and mouse pancreatic cell proliferation and invasion. Notably, the analysis of tumor vasculature revealed a strong increase of pericyte coverage and vessel perfusion both in mPDAC and RIP-Tag2 tumors, in parallel to an inhibition of tumor hypoxia. Nucleolin inhibition directly affected endothelial cell (EC) activation and changed a proangiogenic signature. Among the vascular activators, nucleolin inhibition significantly decreased angiopoietin-2 (Ang-2) secretion and expression in ECs, in the tumor and in the plasma of mPDAC mice. As a consequence of the observed N6L-induced tumor vessel normalization, pre-treatment with N6L efficiently improved chemotherapeutic drug delivery and increased the antitumor properties of gemcitabine in PDAC mice. In conclusion, nucleolin inhibition is a new anti-pancreatic cancer therapeutic strategy that dually blocks tumor progression and normalizes tumor vasculature, improving the delivery and efficacy of chemotherapeutic drugs. Moreover, we unveiled Ang-2 as a potential target and suitable response biomarker for N6L treatment in pancreatic cancer. Cancer Res; 76(24); 7181-93. ©2016 AACR.

First case report of a human sepsis involving a recently identified anaerobic agent: Bacteroides faecis

Up until now, Bacteroides faecis, a Gram-negative, anaerobic, non-motile, nonsporeforming rod has been principally described as a commensal microbe isolated from the feces of healthy adults. We report the first case of human Bacteroides faecis sepsis after removal of suspected post-colonic ischemia colonized epicardic electrodes. Electrodes and blood cultures both grew Gram-negative anaerobic rods but usual phenotypic methods and 16S rARN gene sequencing failed to ensure its species identification. B. faecis was finally identified using hsp60 gene sequencing. Because this species is not well-known and is difficult to identify, it may have been overlooked or misidentified in previous studies.

Transcriptional Coactivator and Chromatin Protein PC4 Is Involved in Hippocampal Neurogenesis and Spatial Memory Extinction

Although the elaborate combination of histone and non-histone protein complexes defines chromatin organization and hence regulates numerous nuclear processes, the role of chromatin organizing proteins remains unexplored at the organismal level. The highly abundant, multifunctional, chromatin-associated protein and transcriptional coactivator positive coactivator 4 (PC4/Sub1) is absolutely critical for life, because its absence leads to embryonic lethality. Here, we report results obtained with conditional PC4 knock-out (PC4(f/f) Nestin-Cre) mice where PC4 is knocked out specifically in the brain. Compared with the control (PC4(+/+) Nestin-Cre) mice, PC4(f/f) Nestin-Cre mice are smaller with decreased nocturnal activity but are fertile and show no motor dysfunction. Neurons in different areas of the brains of these mice show sensitivity to hypoxia/anoxia, and decreased adult neurogenesis was observed in the dentate gyrus. Interestingly, PC4(f/f) Nestin-Cre mice exhibit a severe deficit in spatial memory extinction, whereas acquisition and long term retention were unaffected. Gene expression analysis of the dorsal hippocampus of PC4(f/f) Nestin-Cre mice revealed dysregulated expression of several neural function-associated genes, and PC4 was consistently found to localize on the promoters of these genes, indicating that PC4 regulates their expression. These observations indicate that non-histone chromatin-associated proteins like PC4 play a significant role in neuronal plasticity.

Expression of Nucleolin Affects Microtubule Dynamics

Nucleolin is present in diverse cellular compartments and is involved in a variety of cellular processes from nucleolar structure and function to intracellular trafficking, cell adhesion and migration. Recently, nucleolin has been localized at the mature centriole where it is involved in microtubule nucleation and anchoring. Although this new function of nucleolin linked to microtubule regulation has been identified, the global effects of nucleolin on microtubule dynamics have not been addressed yet. In the present study, we analyzed the roles of nucleolin protein levels on global microtubule dynamics by tracking the EB3 microtubule plus end binding protein in live cells. We have found that during microtubule growth phases, nucleolin affects both the speed and life time of polymerization and by analyzing catastrophe events, we showed that nucleolin reduces catastrophe frequency. This new property of nucleolin was then confirmed in a cold induced microtubule depolymerization experiment in which we have found that cold resistant microtubules were totally destabilized in nucleolin depleted cells. Altogether, our data demonstrate a new function of nucleolin on microtubule stabilization, thus bringing novel insights into understanding the multifunctional properties of nucleolin in healthy and cancer cells.

Diversity of Group I and II Clostridium botulinum Strains from France Including Recently Identified Subtypes

In France, human botulism is mainly food-borne intoxication, whereas infant botulism is rare. A total of 99 group I and II Clostridium botulinum strains including 59 type A (12 historical isolates [1947-1961], 43 from France [1986-2013], 3 from other countries, and 1 collection strain), 31 type B (3 historical, 23 recent isolates, 4 from other countries, and 1 collection strain), and 9 type E (5 historical, 3 isolates, and 1 collection strain) were investigated by botulinum locus gene sequencing and multilocus sequence typing analysis. Historical C. botulinum A strains mainly belonged to subtype A1 and sequence type (ST) 1, whereas recent strains exhibited a wide genetic diversity: subtype A1 in orfX or ha locus, A1(B), A1(F), A2, A2b2, A5(B2') A5(B3'), as well as the recently identified A7 and A8 subtypes, and were distributed into 25 STs. Clostridium botulinum A1(B) was the most frequent subtype from food-borne botulism and food. Group I C. botulinum type B in France were mainly subtype B2 (14 out of 20 historical and recent strains) and were divided into 19 STs. Food-borne botulism resulting from ham consumption during the recent period was due to group II C. botulinum B4. Type E botulism is rare in France, 5 historical and 1 recent strains were subtype E3. A subtype E12 was recently identified from an unusual ham contamination. Clostridium botulinum strains from human botulism in France showed a wide genetic diversity and seems to result not from a single evolutionary lineage but from multiple and independent genetic rearrangements.

Nuclear Functions of Nucleolin through Global Proteomics and Interactomic Approaches

Nucleolin (NCL) is a major component of the cell nucleolus, which has the ability to rapidly shuttle to several other cells' compartments. NCL plays important roles in a variety of essential functions, among which are ribosome biogenesis, gene expression, and cell growth. However, the precise mechanisms underlying NCL functions are still unclear. Our study aimed to provide new information on NCL functions via the identification of its nuclear interacting partners. Using an interactomics approach, we identified 140 proteins co-purified with NCL, among which 100 of them were specifically found to be associated with NCL after RNase digestion. The functional classification of these proteins confirmed the prominent role of NCL in ribosome biogenesis and additionally revealed the possible involvement of nuclear NCL in several pre-mRNA processing pathways through its interaction with RNA helicases and proteins participating in pre-mRNA splicing, transport, or stability. NCL knockdown experiments revealed that NCL regulates the localization of EXOSC10 and the amount of ZC3HAV1, two components of the RNA exosome, further suggesting its involvement in the control of mRNA stability. Altogether, this study describes the first nuclear interactome of human NCL and provides the basis for further understanding the mechanisms underlying the essential functions of this nucleolar protein.

A penicillin- and metronidazole-resistant Clostridium botulinum strain responsible for an infant botulism case

The clinical course of a case of infant botulism was characterized by several relapses despite therapy with amoxicillin and metronidazole. Botulism was confirmed by identification of botulinum toxin and Clostridium botulinum in stools. A C. botulinum A2 strain resistant to penicillins and with heterogeneous resistance to metronidazole was isolated from stool samples up to 110 days after onset. Antibiotic susceptibility was tested by disc agar diffusion and MICs were determined by Etest. Whole genome sequencing allowed detection of a gene cluster composed of blaCBP for a novel penicillinase, blaI for a regulator, and blaR1 for a membrane-bound penicillin receptor in the chromosome of the C. botulinum isolate. The purified recombinant penicillinase was assayed. Resistance to β-lactams was in agreement with the kinetic parameters of the enzyme. In addition, the β-lactamase gene cluster was found in three C. botulinum genomes in databanks and in two of 62 genomes of our collection, all the strains belonging to group I C. botulinum. This is the first report of a C. botulinum isolate resistant to penicillins. This stresses the importance of antibiotic susceptibility testing for adequate therapy of botulism.

Rarimicrobium hominis gen. nov., sp. nov., representing the fifth genus in the phylum Synergistetes that includes human clinical isolates

Five human clinical isolates of an unknown, strictly anaerobic, slow-growing, Gram-stain-negative, rod-shaped micro-organism were subjected to a polyphasic taxonomic study. Comparative 16S rRNA gene sequence-based phylogeny showed that the isolates grouped in a clade that included members of the genera Pyramidobacter, Jonquetella, and Dethiosulfovibrio; the type strain of Pyramidobacter piscolens was the closest relative with 91.5-91.7 % 16S rRNA gene sequence similarity. The novel strains were mainly asaccharolytic and unreactive in most conventional biochemical tests. Major metabolic end products in trypticase/glucose/yeast extract broth were acetic acid and propionic acid and the major cellular fatty acids were C13 : 0 and C16 : 0, each of which could be used to differentiate the strains from P. piscolens. The DNA G+C content based on whole genome sequencing for the reference strain 22-5-S 12D6FAA was 57 mol%. Based on these data, a new genus, Rarimicrobium gen. nov., is proposed with one novel species, Rarimicrobium hominis sp. nov., named after the exclusive and rare finding of the taxon in human samples. Rarimicrobium is the fifth genus of the 14 currently characterized in the phylum Synergistetes and the third one in subdivision B that includes human isolates. The type strain of Rarimicrobium hominis is ADV70T ( = LMG 28163T = CCUG 65426T).

The roles of nucleolin subcellular localization in cancer

Nucleolin (NCL) is one of the most abundant non ribosomal protein of the nucleolus where it plays a central role in polymerase I transcription. NCL is also found outside of the nucleolus, in the nucleoplasm, cytoplasm as well as on the cell membrane. It acts in all cell compartments to control cellular homeostasis and therefore each cellular pool of NCL can play a different role in cancer development. NCL overexpression and its increased localization at the cell membrane is a common feature of several tumor cells. In cancer cells, NCL overexpression influences cell survival, proliferation and invasion through its action on different cellular pathways. In this review, we describe how the multiple functions of NCL that are associated to its multiple cellular localization can participate to the development of cancer.

A vanG-type locus in Clostridium argentinense

OBJECTIVES

The objective was to study a new vanG-type locus in Clostridium argentinense vanGCar and to determine its impact on glycopeptide susceptibility of the host.

METHODS

The whole genome of C. argentinense NCIB 10714 was sequenced using Illumina single-reads sequencing technology. The presence of vanGCar in seven C. argentinense strains was tested by PCR and its expression was tested by quantitative RT-PCR (qRT-PCR). Glycopeptide susceptibility was determined by the Etest procedure.

RESULTS

The vanGCar locus contained four genes encoding a carboxypeptidase, a d-alanine:d-serine ligase, a serine transporter and a serine racemase, and was present in the seven C. argentinense studied. An AraC-type transcriptional regulator was found upstream from the genes. C. argentinense NCIB 10714 was susceptible to vancomycin and to teicoplanin. qRT-PCR experiments revealed that vanGCar was not expressed without or with induction by a subinhibitory concentration of vancomycin.

CONCLUSIONS

The new vanGCar locus was cryptic in C. argentinense and intrinsic to this species. Emergence of vancomycin resistance in C. argentinense due to decryptification of the vanGCar gene cluster could occur.

Centrosomal nucleolin is required for microtubule network organization

Nucleolin is a pleiotropic protein involved in a variety of cellular processes. Although multipolar spindle formation has been observed after nucleolin depletion, the roles of nucleolin in centrosome regulation and functions have not been addressed. Here we report using immunofluorescence and biochemically purified centrosomes that nucleolin co-localized only with one of the centrioles during interphase which was further identified as the mature centriole. Upon nucleolin depletion, cells exhibited an amplification of immature centriole markers surrounded by irregular pericentrin staining; these structures were exempt from maturation markers and unable to nucleate microtubules. Furthermore, the microtubule network was disorganized in these cells, exhibiting frequent non-centrosomal microtubules. At the mature centriole a reduced kinetics in the centrosomal microtubule nucleation phase was observed in live silenced cells, as well as a perturbation of microtubule anchoring. Immunoprecipitation experiments showed that nucleolin belongs to protein complexes containing 2 key centrosomal proteins, γ-tubulin and ninein, involved in microtubule nucleation and anchoring steps. Altogether, our study uncovered a new role for nucleolin in restricting microtubule nucleation and anchoring at centrosomes in interphase cells.

Haemorrhagic toxin and lethal toxin from Clostridium sordellii strain vpi9048: molecular characterization and comparative analysis of substrate specificity of the large clostridial glucosylating toxins

Large clostridial glucosylating toxins (LCGTs) are produced by toxigenic strains of Clostridium difficile, Clostridium perfringens, Clostridium novyi and Clostridium sordellii. While most C. sordellii strains solely produce lethal toxin (TcsL), C. sordellii strain VPI9048 co-produces both hemorrhagic toxin (TcsH) and TcsL. Here, the sequences of TcsH-9048 and TcsL-9048 are provided, showing that both toxins retain conserved LCGT features and that TcsL and TcsH are highly related to Toxin A (TcdA) and Toxin B (TcdB) from C. difficile strain VPI10463. The substrate profile of the toxins was investigated with recombinant LCGT transferase domains (rN) and a wide panel of small GTPases. rN-TcsH-9048 and rN-TcdA-10463 glucosylated preferably Rho-GTPases but also Ras-GTPases to some extent. In this respect, rN-TcsH-9048 and rN-TcdA-10463 differ from the respective full-length TcsH-9048 and TcdA-10463, which exclusively glucosylate Rho-GTPases. rN-TcsL-9048 and full length TcsL-9048 glucosylate both Rho- and Ras-GTPases, whereas rN-TcdB-10463 and full length TcdB-10463 exclusively glucosylate Rho-GTPases. Vero cells treated with full length TcsH-9048 or TcdA-10463 also showed glucosylation of Ras, albeit to a lower extent than of Rho-GTPases. Thus, in vitro analysis of substrate spectra using recombinant transferase domains corresponding to the auto-proteolytically cleaved domains, predicts more precisely the in vivo substrates than the full length toxins. Except for TcdB-1470, all LCGTs evoked increased expression of the small GTPase RhoB, which exhibited cytoprotective activity in cells treated with TcsL isoforms, but pro-apoptotic activity in cells treated with TcdA, TcdB, and TcsH. All LCGTs induced a rapid dephosphorylation of pY118-paxillin and of pS144/141-PAK1/2 prior to actin filament depolymerization indicating that disassembly of focal adhesions is an early event leading to the disorganization of the actin cytoskeleton.

Veillonella seminalis sp. nov., a novel anaerobic Gram-stain-negative coccus from human clinical samples, and emended description of the genus Veillonella

Ten isolates of unknown, Gram-stain-negative, anaerobic cocci were recovered from human clinical samples, mainly from semen. On the basis of their phenotypic features, including morphology, main metabolic end products, gas production, nitrate reduction and decarboxylation of succinate, the strains were identified as members of the genus Veillonella. Multi-locus sequence analysis and corresponding phylogenies were based on 16S rRNA, dnaK and rpoB genes, and on the newly proposed gltA gene. The strains shared high levels of genetic sequence similarity and were related most closely to Veillonella ratti. The strains could not be differentiated from V. ratti on the basis of 16S rRNA gene sequence analysis while gltA, rpoB and dnaK gene sequences showed 85.1, 93.5 and 90.2% similarity with those of the type strain of V. ratti, respectively. Phylogenetic analyses revealed that the isolates formed a robust clade in the V. ratti-Veillonella criceti-Veillonella magna subgroup of the genus Veillonella. As observed for V. criceti, the isolates were able to ferment fructose. In contrast to other members of the genus Veillonella, the 10 strains were not able to metabolize lactate. Cellular fatty acid composition was consistent with that of other species of the genus Veillonella. From these data, the 10 isolates are considered to belong to a novel species in the genus Veillonella, for which the name Veillonella seminalis sp. nov. is proposed. The type strain is ADV 4313.2(T) ( = CIP 107810(T) = LMG 28162(T)). Veillonella strain ACS-216-V-Col6b subjected to whole genome sequencing as part as the Human Microbiome Project is another representative of V. seminalis sp. nov. An emended description of the genus Veillonella is also proposed.

Centromeric histone variant CENP-A represses acetylation-dependent chromatin transcription that is relieved by histone chaperone NPM1

Mammalian centromeric histone H3 variant, CENP-A, is involved in maintaining the functional integrity and epigenetic inheritance of the centromere. CENP-A causes transcriptional repression of centromeric chromatin through an unknown mechanism. Here, we report that reconstituted CENP-A nucleosomes are amenable to ATP-dependent SWI/SNF-mediated remodelling but are less permissive to acetylation and acetylation-dependent in vitro chromatin transcription. Remarkably, the transcriptional repression of the CENP-A chromatinized template could be relieved by the ectopic addition of histone chaperone, nucleophosmin.

A duplicated NUCLEOLIN gene with antagonistic activity is required for chromatin organization of silent 45S rDNA in Arabidopsis

In plants as well as in animals, hundreds to thousands of 45S rRNA gene copies localize in Nucleolus Organizer Regions (NORs), and the activation or repression of specific sets of rDNA depends on epigenetic mechanisms. Previously, we reported that the Arabidopsis thaliana nucleolin protein NUC1, an abundant and evolutionarily conserved nucleolar protein in eukaryotic organisms, is required for maintaining DNA methylation levels and for controlling the expression of specific rDNA variants in Arabidopsis. Interestingly, in contrast with animal or yeast cells, plants contain a second nucleolin gene. Here, we report that Arabidopsis NUC1 and NUC2 nucleolin genes are both required for plant growth and survival and that NUC2 disruption represses flowering. However, these genes seem to be functionally antagonistic. In contrast with NUC1, disruption of NUC2 induces CG hypermethylation of rDNA and NOR association with the nucleolus. Moreover, NUC2 loss of function triggers major changes in rDNA spatial organization, expression, and transgenerational stability. Our analyses indicate that silencing of specific rRNA genes is mostly determined by the active or repressed state of the NORs and that nucleolin proteins play a key role in the developmental control of this process.

Eisenbergiella tayi gen. nov., sp. nov., isolated from human blood

A catalase-positive, rod-shaped, non-proteolytic, non-motile, anaerobic bacterial strain, designated B086562T, was isolated from a blood culture of an 84-year-old male patient in Israel. According to 16S rRNA gene sequence phylogeny, this strain has no known close relatives among recognized bacteria but should be placed within the family Lachnospiraceae . The most closely related recognized bacteria were from the ‘ Clostridium clostridioforme group’: C. clostridioforme (92.4 %) and Clostridium bolteae (92.3 %). The isolate produced butyrate, lactate, acetate and succinate as major metabolic end products. The major fatty acids were C16 : 0 and C18 : 1 cis 9 DMA and the DNA G+C content was 46.0 mol%. On the basis of the phenotypic properties and phylogenetic distinctiveness, the blood isolate represents a novel species of a new genus in the family Lachnospiraceae , for which the name Eisenbergiella tayi gen. nov., sp. nov. is proposed. The type strain of Eisenbergiella tayi is B086562T ( = LMG 27400T = DSM 26961T = ATCC BAA-2558T).

macroH2A1 histone variant represses rDNA transcription

The regulation of ribosomal DNA transcription is an important step for the control of cell growth. Epigenetic marks such as DNA methylation and posttranslational modifications of canonical histones have been involved in this regulation, but much less is known about the role of histone variants. In this work, we show that the histone variant macroH2A1 is present on the promoter of methylated rDNA genes. The inhibition of the expression of macroH2A1 in human HeLa and HepG2 cells and in a mouse ES cell line resulted in an up to 5-fold increase of pre-rRNA levels. This increased accumulation of pre-rRNA is accompanied by an increase of the loading of RNA polymerase I and UBF on the rDNA without any changes in the number of active rDNA genes. The inhibition of RNA polymerase I transcription by actinomycin D or by knocking down nucleolin, induces the recruitment of macroH2A1 on the rDNA and the relocalization of macroH2A1 in the nucleolus. Interestingly, the inhibition of rDNA transcription induced by nucleolin depletion is alleviated by the inactivation of macroH2A1. These results demonstrate that macroH2A1 is a new factor involved in the regulation of rDNA transcription.

p53 acts as a safeguard of translational control by regulating fibrillarin and rRNA methylation in cancer

Ribosomes are specialized entities that participate in regulation of gene expression through their rRNAs carrying ribozyme activity. Ribosome biogenesis is overactivated in p53-inactivated cancer cells, although involvement of p53 on ribosome quality is unknown. Here, we show that p53 represses expression of the rRNA methyl-transferase fibrillarin (FBL) by binding directly to FBL. High levels of FBL are accompanied by modifications of the rRNA methylation pattern, impairment of translational fidelity, and an increase of internal ribosome entry site (IRES)-dependent translation initiation of key cancer genes. FBL overexpression contributes to tumorigenesis and is associated with poor survival in patients with breast cancer. Thus, p53 acts as a safeguard of protein synthesis by regulating FBL and the subsequent quality and intrinsic activity of ribosomes.

Characterization of the enzymatic activity of Clostridium perfringens TpeL

TpeL is a toxin produced by Clostridium perfringens which belongs to the large clostridial glucosylating toxin family. It was shown that TpeL modifies Ras using UDP-glucose or UDP-N-acetylglucosamine as cosubstrates (Guttenberg et al., 2012; Nagahama et al., 2011). We confirmed that TpeL preferentially glucosaminates the three isoforms of Ras (cH-Ras, N-Ras, and K-Ras) from UDP-N-acetylglucosamine and to a lower extent Rap1a and R-Ras3, and very weakly Rac1. In contrast to previous report, we observed that Ral was not a substrate of TpeL. In addition, we confirmed by in vitro glucosylation and mass spectrometry that TpeL modifies cH-Ras at Thr35.

Characterization of nucleolin K88 acetylation defines a new pool of nucleolin colocalizing with pre-mRNA splicing factors

Nucleolin is a multifunctional protein that carries several post-translational modifications. We characterized nucleolin acetylation and developed antibodies specific to nucleolin K88 acetylation. Using this antibody we show that nucleolin is acetylated in vivo and is not localized in the nucleoli, but instead is distributed throughout the nucleoplasm. Immunofluorescence studies indicate that acetylated nucleolin is co-localized with the splicing factor SC35 and partially with Y12. Acetylated nucleolin is expressed in all tested proliferating cell types. Our findings show that acetylation defines a new pool of nucleolin which support a role for nucleolin in the regulation of mRNA maturation and transcription by RNA polymerase II.

Chromatin structure and organization: the relation with gene expression during development and disease

The elementary level of chromatin fiber, namely the nucleofilament, is known to undergo a hierarchical compaction leading to local chromatin loops, then chromatin domains and ultimately chromosome territories. These successive folding levels rely on the formation of chromatin loops ranging from few kb to some Mb. In addition to a packaging and structural role, the high-order organization of genomes functionally impacts on gene expression program. This review summarises to which extent each level of chromatin compaction does affect gene regulation. In addition, we point out the structural and functional changes observed in diseases. Emphasis will be mainly placed on the large-scale organization of the chromatin.

First case of intra-abdominal infection with Clostridium disporicum

We describe a case of post-operative intra-abdominal infection with Clostridium disporicum, a gram-positive anaerobic rod rarely isolated in clinical specimens. Its typical doubled-spored form, when present, facilitates its recognition. Phenotype-based identification methods used here were not reliable and a 16S rRNA sequence analysis was needed.

Interaction of nucleolin with ribosomal RNA genes and its role in RNA polymerase I transcription

Nucleolin is a multi-functional nucleolar protein that is required for ribosomal RNA gene (rRNA) transcription in vivo, but the mechanism by which nucleolin modulates RNA polymerase I (RNAPI) transcription is not well understood. Nucleolin depletion results in an increase in the heterochromatin mark H3K9me2 and a decrease in H4K12Ac and H3K4me3 euchromatin histone marks in rRNA genes. ChIP-seq experiments identified an enrichment of nucleolin in the ribosomal DNA (rDNA) coding and promoter region. Nucleolin is preferentially associated with unmethylated rRNA genes and its depletion leads to the accumulation of RNAPI at the beginning of the transcription unit and a decrease in UBF along the coding and promoter regions. Nucleolin is able to affect the binding of transcription termination factor-1 on the promoter-proximal terminator T0, thus inhibiting the recruitment of TIP5 and HDAC1 and the establishment of a repressive heterochromatin state. These results reveal the importance of nucleolin for the maintenance of the euchromatin state and transcription elongation of rDNA.

Clostridium celerecrescens, often misidentified as "Clostridium clostridioforme group," is involved in rare human infection cases

Misidentification of rare Clostridium species often originated from the environment as clinically relevant species is problematic. A strain isolated from a traumatic leg wound first identified as C. clostridioforme was finally identified as the rare Clostridium celerecrescens. Two similar misidentifications are reported in the literature. In order to help the phenotypic differentiation of C. celerecrescens from the close species of the "C. clostridioforme group", an identification table and differential susceptibilities to 4 selected antibiotics are proposed. Once a clinical isolate is referred to this group, identification should be definitively confirmed by unambiguous methods such as 16s rDNA sequencing.

3D chromatin conformation correlates with replication timing and is conserved in resting cells

Although chromatin folding is known to be of functional importance to control the gene expression program, less is known regarding its interplay with DNA replication. Here, using Circular Chromatin Conformation Capture combined with high-throughput sequencing, we identified megabase-sized self-interacting domains in the nucleus of a human lymphoblastoid cell line, as well as in cycling and resting peripheral blood mononuclear cells (PBMC). Strikingly, the boundaries of those domains coincide with early-initiation zones in every cell types. Preferential interactions have been observed between the consecutive early-initiation zones, but also between those separated by several tens of megabases. Thus, the 3D conformation of chromatin is strongly correlated with the replication timing along the whole chromosome. We furthermore provide direct clues that, in addition to the timing value per se, the shape of the timing profile at a given locus defines its set of genomic contacts. As this timing-related scheme of chromatin organization exists in lymphoblastoid cells, resting and cycling PBMC, this indicates that it is maintained several weeks or months after the previous S-phase. Lastly, our work highlights that the major chromatin changes accompanying PBMC entry into cell cycle occur while keeping largely unchanged the long-range chromatin contacts.

Nucleolin interacts with US11 protein of herpes simplex virus 1 and is involved in its trafficking

Herpes simplex virus type 1 (HSV-1) infection induces profound nucleolar modifications at the functional and organizational levels, including nucleolar invasion by several viral proteins. One of these proteins is US11, which exhibits several different functions and displays both cytoplasmic localization and clear nucleolar localization very similar to that of the major multifunctional nucleolar protein nucleolin. To determine whether US11 interacts with nucleolin, we purified US11 protein partners by coimmunoprecipitations using a tagged protein, Flag-US11. From extracts of cells expressing Flag-US11 protein, we copurified a protein of about 100 kDa that was further identified as nucleolin. In vitro studies have demonstrated that nucleolin interacts with US11 and that the C-terminal domain of US11, which is required for US11 nucleolar accumulation, is sufficient for interaction with nucleolin. This association was confirmed in HSV-1-infected cells. We found an increase in the nucleolar accumulation of US11 in nucleolin-depleted cells, thereby revealing that nucleolin could play a role in US11 nucleocytoplasmic trafficking through one-way directional transport out of the nucleolus. Since nucleolin is required for HSV-1 nuclear egress, the interaction of US11 with nucleolin may participate in the outcome of infection.