Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Nucleolin”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 145 records · Page 8Linked to original sources
PubMed2001

Identification of nucleolin as a glucocorticoid receptor interacting protein.

The glucocorticoid receptor (GR) is a ligand-induced transcription factor which modulates the transcriptional activity of target genes. Full transcriptional activity of GR is achieved with the help of accessory proteins that are able to interact with GR. We have identified a 95-kDa protein by a blotting technique which utilizes a radioactively labeled DNA-bound GR to detect proteins that bind to this complex. Biochemical purification of this protein followed by protein microsequencing resulted in the identification of human nucleolin. In addition we could show that a GR-deletion mutant localizes to the nucleolus, where nucleolin is one of the most abundant proteins. The binding of nucleolin to this deletion mutant was demonstrated by GST-pull-down experiments. We suggest a biological role of nucleolin in binding of GR in the nucleolus.

Animals↗
PubMed2000

Nucleolin as the earliest target molecule of autoantibodies produced in MRL/lpr lupus-prone mice.

To elucidate the autoantigen against which autoantibodies are produced in the earliest phase of the disease process of systemic lupus erythematosus (SLE), serum samples were collected individually and serially from 10 NZB/NZW F1 and 10 MRL/lpr mice. Using immunoblots with mouse thymoma cell (EL-4) lysates as substrates, all mice were found to generate autoantibody against an either 150-kDa, 110-kDa, 75-kDa, or 55-kDa molecule in as early as 4 weeks. Anti-DNA antibodies occurred almost at the same time or after those against these four molecules. The number of antigens reactive with autoantibodies in immunoblots increased gradually with age. Antibodies against histone molecules were produced after 8 weeks of age. Among the four antigens, the 110-kDa molecule was identified as nucleolin, which is an abundant nucleolar phosphoprotein. Nucleolin binds DNA, RNA, and nucleic acid-binding proteins such as histone H1. Nucleolin is a target of granzyme A of cytotoxic T cells, and autoantibodies against it are found in sera from patients with SLE as well as from those with various viral infections. These results indicate that nucleolin is one of the immunodominant molecules that break down self-tolerance and initiate autoantibody-spreading in a mouse model of SLE.

Aging↗
PubMed1992

Autoantibodies to nucleolin cross-react with histone H1 in systemic lupus erythematosus.

IgM autoantibodies to nucleolin and histone H1 are strongly associated in the serum of patients with systemic lupus erythematosus. IgM eluted from immobilized nucleolin specifically stained histone H1 blotted to nitrocellulose; conversely, IgM eluates prepared from immobilized histone H1 stained nucleolin blots. We conclude that the linkage of anti-nucleolin and anti-histone H1 autoantibodies in SLE is due, at least in part, to immunologic cross-reactivity between these two autoantigens, which share certain similar structural features.

Adult↗
PubMed1997

NopA64, a novel nucleolar phosphoprotein from proliferating onion cells, sharing immunological determinants with mammalian nucleolin.

Five major soluble nuclear proteins associated with cell proliferation were identified in Allium cepa L. root cells. One of them, of 64 kDa, was revealed by Western blotting with anti-mammalian nucleolin antibodies. A polyclonal antibody raised against this protein, which we have named NopA64, localised it in the nucleolus as well as in nuclear coiled bodies. Together with NopA64, the antibody also revealed a smaller form, called NopA61. Both proteins were present in the soluble ribonucleoprotein fraction and in the nuclear matrix of proliferating cells, but NopA61 was the only form revealed in differentiated cells. NopA64 contained epitopes also present in other plants, in mammalian nucleolin and in its yeast homologue, gar2. In mammals, the highest homology was with 50-kDa nucleolin fragments containing the RNA-binding motifs and the glycine-arginine-rich (GAR) domain. NopA64 was moderately phosphorylated in vitro by exogenous casein kinase II and cdc2 kinase, whereas NopA61 was highly phosphorylated by casein kinase II. Furthermore, NopA61 was the only band detected after dephosphorylation as well as after endoproteolysis of NopA64. This protein could be one of the various functional homologues of mammalian nucleolin in plant cells.

Allium↗
PubMed1991

Nucleolin promotes secondary structure in ribosomal RNA.

The effect of nucleolin on the secondary structure of RNA was studied using circular dichroism (CD). Nucleolin caused decreases in the main positive bands and shifts to higher wavelengths in the CD spectra of synthetic polynucleotides such as poly(G) and poly(A) indicating helix destabilizing activity. In contrast, nucleolin effected increases in signal and shifts to lower wavelengths of the peaks of CD spectra of ribosomal RNA, suggesting enhancement of secondary structure. Another major nucleolar RNA binding protein, B23, had helix destabilizing activity but did not enhance RNA secondary structure. It is proposed that nucleolin promotes formation of secondary structure in preribosomal RNA during the early stages of ribosome biogenesis.

Animals↗
PubMed1988

Structure of the mouse nucleolin gene. The complete sequence reveals that each RNA binding domain is encoded by two independent exons.

Nucleolin is a multifunctional nucleolar protein involved in the synthesis, packaging and maturation of pre-rRNA in eukaryotic cells. We describe the molecular organization and complete sequence of the mouse nucleolin gene, the first higher eukaryotic gene encoding a protein that is both an RNA binding protein involved in rRNA processing and a specific nucleolar protein. The nucleolin gene extends over 9000 base-pairs and is split into 14 exons that encode the 706 amino acid residues of the protein. The promoter sequence is G + C-rich (67% G + C) with four G/C boxes, it lacks bona fide TATA and CAAT boxes and shows capping site heterogeneity. The existence of pyrimidine-rich motifs, similar to those found in the promoter of ribosomal protein genes, could be relevant to the co-regulation of genes whose products are involved in ribosome biogenesis. Nucleolin contains four RNA binding domains, each about 80 amino acid residues long, which include the 11-residue core ribonucleoprotein consensus motif. Each domain is encoded by two exons, with an intervening sequence interrupting the conserved core motif at roughly the same amino acid position. This latter result suggests that the RNA binding domains are composed of two independent subdomains, whose functions remain to be determined.

Amino Acid Sequence↗
PubMed2005

The Gly-Arg-rich C-terminal domain of pea nucleolin is a DNA helicase that catalytically translocates in the 5'- to 3'-direction.

Nucleolin is a major nucleolar phosphoprotein of exponentially growing eukaryotic cells. Here we report the cloning, purification, and characterization of the C-terminal glycine/arginine-rich (GAR) domain of pea nucleolin. The purified recombinant protein (17 kDa) shows ATP-/Mg(2+)-dependent DNA helicase and ssDNA-/Mg(2+)-dependent ATPase activities. The enzyme unwinds DNA in the 5'- to 3'-direction, which is the first report in plant for this directional activity. It unwinds forked/non-forked DNA with equal efficiency. The anti-nucleolin antibodies immunodepleted the activities of the enzyme. The DNA interacting ligands nogalamycin, daunorubicin, actinomycin C1, and ethidium bromide were inhibitory to DNA unwinding (with K(i) values of 0.40, 2.21, 8.0, and 9.0 microM, respectively) and ATPase (with K(i) values of 0.43, 1.65, 4.6, and 7.0 microM, respectively) activities of the enzyme. This study confirms that the unwinding and ATPase activities of pea nucleolin resided in the GAR domain. This study should make important contribution to our better understanding of DNA transaction in plants, mechanism of DNA unwinding, and the mechanism by which these ligands can disturb genome integrity.

Adenosine Triphosphatases↗
PubMed2005

Regulation of p53 translation and induction after DNA damage by ribosomal protein L26 and nucleolin.

Increases in p53 protein levels after DNA damage have largely been attributed to an increase in the half-life of p53 protein. Here we demonstrate that increased translation of p53 mRNA is also a critical step in the induction of p53 protein in irradiated cells. Ribosomal protein L26 (RPL26) and nucleolin were found to bind to the 5' untranslated region (UTR) of p53 mRNA and to control p53 translation and induction after DNA damage. RPL26 preferentially binds to the 5'UTR after DNA damage, and its overexpression enhances association of p53 mRNA with heavier polysomes, increases the rate of p53 translation, induces G1 cell-cycle arrest, and augments irradiation-induced apoptosis. Opposite effects were seen when RPL26 expression was inhibited. In contrast, nucleolin overexpression suppresses p53 translation and induction after DNA damage, whereas nucleolin downregulation promotes p53 expression. These findings demonstrate the importance of increased translation of p53 in DNA-damage responses and suggest critical roles for RPL26 and nucleolin in affecting p53 induction.

5' Untranslated Regions↗
PubMed2003

An increased expression of nucleolin is associated with a physiological nucleolar segregation.

Nucleolar segregation is the most striking cellular phenotypic feature of cold-acclimatized carp and depicts the cyclical reprogramming that the physiology of the fish undergoes between summer and winter, where a clear differential expression of some nucleolar related genes occurs. We characterized carp nucleolin, a nucleolar protein involved in multiple steps of ribosome biogenesis, and evaluated its expression upon fish acclimatization. We show that the carp cDNA deduced amino acid sequence exhibits the same tripartite structural organization found in other species. Nevertheless, we observed that nucleolin mRNA expression was strongly induced in the cold-adapted carp as was the nuclear protein content, assessed by immunocytochemistry in liver sections. The physiological up-regulation of nucleolin in the cold-acclimatized carp, where rRNA transcription and processing are depressed concomitantly with the nucleolus segregation, is consistent with the notion that nucleolin plays a fundamental role in repressing rRNA synthesis.

Acclimatization↗
PubMed2003

Centaurin-alpha 1 associates in vitro and in vivo with nucleolin.

Centaurin-alpha(1) was originally described as a binding partner for phosphoinositides. In spite of the presence of a putative ADP-ribosylation factor (ARF) GTPase-activating protein (GAP) domain, no ARF-GAP activity has been attributed to centaurin-alpha(1) so far. Thus the function of this protein remains to be determined. In order to better understand its intracellular role, we aimed to identify centaurin-alpha(1) partners. Using affinity chromatography followed by mass spectrometry analysis, we identified several potential centaurin-alpha(1) protein partners. Nucleolin, a nucleolar protein involved in ribosome biosynthesis, was the main centaurin-alpha(1) interacting protein. The interaction between centaurin-alpha(1) and nucleolin was confirmed by Western blot analysis and GST pull down assays. Moreover, we have shown that ectopically expressed centaurin-alpha(1) associates in vivo with endogenous nucleolin in human embryonic kidney 293 cells. In addition, the association between nucleolin and centaurin-alpha(1) was disrupted by RNAse treatment, indicating that RNA integrity was necessary for their binding. This suggested that centaurin-alpha(1) was part of a ribonucleoprotein complex.

Adaptor Proteins, Signal Transducing↗
PubMed1990

A protein partially expressed on the surface of HepG2 cells that binds lipoproteins specifically is nucleolin.

Nucleolin, a major nucleolar protein of rapidly growing eukaryotic cells, has been thought to be predominantly if not exclusively located in the nucleolus. Recent data however [Borer, R.A., Lehner, C.F., Eppenberger, H.M., & Nigg, N.A. (1989) Cell 56, 379-390] suggest that the protein shuttles constantly between the nucleus and cytoplasm. Ligand blotting studies of whole cell extracts of HepG2 cells identified, in addition to the LDL receptor, another LDL binding protein of Mr 109,000. The 109-kDa protein was partially purified by HPLC and, like the LDL receptor, bound apoB- and apoE-containing lipoproteins but not HDL. However, unlike the LDL receptor, the 109-kDa protein bound lipoproteins in the presence of EDTA and reducing agents, had a lower affinity for lipoproteins than the LDL receptor, and did not react with two antibodies raised against the LDL receptor. The protein sequences of three separate peptides derived from the partially purified 109-kDa species were determined and were identical except for one residue to three separate regions of the published sequence of nucleolin. On immunoblot analysis the 109-kDa protein reacted with a nucleolin-specific antibody, and purified nucleolin reacted both with anti-109-kDa antibody and with LDL. When intact HepG2 cells were treated with Pronase before harvest, there was a 46% decrease in 109-kDa protein while recovery of actin, an intracellular protein, was unaffected. When intact HepG2 cells were surface iodinated and the proteins subjected to HPLC fractionation, the 109-kDa protein was found to be iodinated.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1998

Nucleolin promotes homologous DNA pairing in vitro.

We purified to near homogeneity a previously identified 100 kDa mammalian homologous DNA pairing protein. The purified 100 kDa protein also catalyzed high levels of cell-free homologous DNA recombination activity. This ATP-dependent activity was capable of forming conservative recombinant products between two circular, double-stranded DNA molecules. We were unable to detect any DNA polymerase, DNA ligase, or 5' or 3' exonuclease activity associated with this purified material. The purified 100 kDa protein bound silver nitrate as well as a monoclonal antibody specific for nucleolin. A recombinant protein comprised of the Escherichia coli maltos-ebinding protein fused to the carboxyl-terminal two-thirds of human nucleolin possessed homologous DNA pairing activity. These data indicate that the 100 kDa homologous DNA pairing protein is nucleolin. The observation that nucleolin can carry out homologous DNA strand pairing in vitro raises the prospect that it may function similarly in vivo.

Base Pairing↗
PubMed2006

Nucleolin is a histone chaperone with FACT-like activity and assists remodeling of nucleosomes.

Remodeling machines play an essential role in the control of gene expression, but how their activity is regulated is not known. Here we report that the nuclear protein nucleolin possesses a histone chaperone activity and that this factor greatly enhances the activity of the chromatin remodeling machineries SWI/SNF and ACF. Interestingly, nucleolin is able to induce the remodeling by SWI/SNF of macroH2A, but not of H2ABbd nucleosomes, which are otherwise resistant to remodeling. This new histone chaperone promotes the destabilization of the histone octamer, helping the dissociation of a H2A-H2B dimer, and stimulates the SWI/SNF-mediated transfer of H2A-H2B dimers. Furthermore, nucleolin facilitates transcription through the nucleosome, which is reminiscent of the activity of the FACT complex. This work defines new functions for histone chaperones in chromatin remodeling and regulation of transcription and explains how nucleolin could act on transcription.

Animals↗
PubMed2003

Bidirectional DNA unwinding by a ternary complex of T antigen, nucleolin and topoisomerase I.

The simian virus 40 large tumour-antigen (T antigen) DNA helicase is a hexameric structure; it has been proposed that, in viral DNA replication, two of these hexamers are combined to form a bipartite holoenzyme that acts concurrently at both forks of a replication bubble. In a search for structural components of this helicase complex, we have identified nucleolin as a specific binding protein for the T-antigen hexamer. We show that nucleolin, in co-operation with human topoisomerase I, mediates the cohesion of the T-antigen helicase holoenzyme during plasmid unwinding. Our results provide biochemical evidence for a direct role of nucleolin in DNA replication, in addition to its known function in ribosome biogenesis. The data presented here suggest that nucleolin enables the formation of a functional 'helicase-swivelase' complex at the replication fork.

Amino Acid Sequence↗
PubMed1996

Identification of a nucleolin binding site in human topoisomerase I.

DNA topoisomerase I (topo I) is involved in the regulation of DNA supercoiling, gene transcription, and rDNA recombination. However, little is known about interactions between topo I and other nuclear proteins. We used affinity chromatography with a topo I fusion protein to screen U-937 leukemic cell extracts and have identified nucleolin as a topo I-binding protein. Coimmunoprecipitation and other studies demonstrate that the interaction between topo I and nucleolin is direct. Furthermore, deletion analyses have identified the 166-210-amino acid region of topo I as sufficient for the interaction with nucleolin. Since nucleolin has been implicated in nuclear transport and in a variety of transcriptional processes, the interaction with topo I may relate to the cellular localization of topo I or to the known role of this topoisomerase in transcription.

Amino Acid Sequence↗
PubMed2000

Intracellular redistribution of nucleolin upon interaction with the CD3epsilon chain of the T cell receptor complex.

T cell activation through the antigen receptor (TCR) involves the cytoplasmic tails of the CD3 subunits CD3gamma, CD3delta, CD3epsilon, and CD3zeta. Whereas the biological significance of the cytoplasmic tails of these molecules is suggested, in part, by their evolutionarily conserved sequences, their interactions with signal transduction molecules are not completely understood. We used affinity chromatography columns of glutathione S-transferase fused to the CD3epsilon cytoplasmic tail to isolate proteins that specifically interact with this subunit. In this way, we identified the shuttling protein nucleolin as a specific CD3epsilon-interacting molecule. Using competition studies and affinity chromatography on peptide columns, we were able to identify a central proline-rich sequence as the nucleolin-interacting sequence in CD3epsilon. Transfection in COS cells of wild type CD3epsilon, but not of nonbinding mutants of CD3epsilon, resulted in redistribution of nucleolin from the nucleus and nucleoli to the cytoplasm. This property was transferred to a CD8 protein chimera by appending the cytoplasmic tail of CD3epsilon. We also found that nucleolin associated with the TCR complex. This association was increased upon TCR engagement, suggesting that the CD3epsilon/nucleolin interaction may have a role in T cell activation.

Amino Acid Sequence↗
PubMed2004

Nucleolin interacts with telomerase.

Telomerase is a specialized reverse transcriptase composed of core RNA and protein subunits which plays essential roles in maintaining telomeres in actively dividing cells. Recent work indicates that telomerase shuttles between subcellular compartments during assembly and in response to specific stimuli. In particular, telomerase colocalizes with nucleoli in normal human fibroblasts. Here, we show that nucleolin, a major nucleolar phosphoprotein, interacts with telomerase and alters its subcellular localization. Nucleolin binds the human telomerase reverse transcriptase subunit (hTERT) through interactions with its RNA binding domain 4 and carboxyl-terminal RGG domain, and this binding also involves the telomerase RNA subunit hTERC. The protein-protein interaction between nucleolin and hTERT is critical for the nucleolar localization of hTERT. These findings indicate that interaction of hTERT and nucleolin participates in the dynamic intracellular localization of telomerase complex.

Catalytic Domain↗
PubMed1998

Nucleolin: a multifunctional major nucleolar phosphoprotein.

Nucleolin is a major protein of exponentially growing eukaryotic cells where it is present in abundance at the heart of the nucleolus. It is highly conserved during evolution. Nucleolin contains a specific bipartite nuclear localization signal sequence and possesses a number of unusual structural features. It has unique tripartite structure and each domain performs a specific function by interacting with DNA or RNA or proteins. Nucleolin exhibits intrinsic self-cleaving, DNA helicase, RNA helicase and DNA-dependent ATPase activities. Nucleolin also acts as a sequence-specific RNA binding protein, an autoantigen, and as the component of a B cell specific transcription factor. Its phosphorylation by cdc2, CK2, and PKC-zeta modulate some of its activities. This multifunctional protein has been implicated to be involved directly or indirectly in many metabolic processes such as ribosome biogenesis (which includes rDNA transcription, pre-rRNA synthesis, rRNA processing, ribosomal assembly and maturation), cytokinesis, nucleogenesis, cell proliferation and growth, cytoplasmic-nucleolar transport of ribosomal components, transcriptional repression, replication, signal transduction, inducing chromatin decondensation and many more (see text). In plants it is developmentally, cell-cycle, and light regulated. The regulation of all these functions of a single protein seems to be a challenging puzzle.

Animals↗