Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “nuclear localization”

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 451 records · Page 25Linked to original sources
PubMed2000

Characterization of the nuclear localization signal in the DNA helicase responsible for Bloom syndrome.

Bloom syndrome (BS) is a rare genetic disorder characterized by small body size, photosensitivity, immunodeficiency and a high predisposition to various types of cancer. BLM was identified as the causative gene for BS. The BLM protein is homologous to DNA helicase and has two basic amino acid clusters in its C-terminal region. Previously, we reported that the distal arm of these basic amino acids clusters in the BLM protein functioned as the nuclear localization signal (NLS) of the protein. In this study, we generated plasmid constructs for expression of enhanced green fluorescent protein (EGFP) fused with various BLM protein variants having a mutation with deletions or substitutions in the basic amino acid and analyzed the subcellular localization of the expressed proteins. The EGFP-fused protein containing the basic amino acid cluster region proximal to the C-terminus of BLM helicase was localized exclusively in the nucleus. However, the EGFP-BLM proteins that lacked either Arg1344 or Lys1346 distributed in both the cytoplasm and the nucleus equally. Deletion of Arg1347 also resulted in localization in both the nucleus and cytoplasm, and substitution of Arg1344, Lys1346, Arg1347 or Arg1348 with non-basic amino acids reduced the nuclear localization of BLM protein. Mouse BLM protein which also migrate to the nucleus has two basic amino acid clusters in the C-terminus and the basic amino acids (Lys1346-Pro1347-Lys1348-Arg1349-Arg1350) proximal to the C-terminus are conserved between mouse and human. These findings suggest that the Arg1344-Ser1345-Lys1346-Arg1347 sequence at the C-terminus of the human BLM protein is essential for nuclear localization of this protein.

Adenosine Triphosphatases↗
PubMed1998

Identification and functional characterization of a novel nuclear localization signal present in the yeast Nab2 poly(A)+ RNA binding protein.

The nuclear import of proteins bearing a basic nuclear localization signal (NLS) is dependent on karyopherin alpha/importin alpha, which acts as the NLS receptor, and karyopherin beta1/importin beta, which binds karyopherin alpha and mediates the nuclear import of the resultant ternary complex. Recently, a second nuclear import pathway that allows the rapid reentry into the nucleus of proteins that participate in the nuclear export of mature mRNAs has been identified. In mammalian cells, a single NLS specific for this alternate pathway, the M9 NLS of heterogeneous nuclear ribonucleoprotein A1 (hnRNPA1), has been described. The M9 NLS binds a transport factor related to karyopherin beta1, termed karyopherin beta2 or transportin, and does not require a karyopherin alpha-like adapter protein. A yeast homolog of karyopherin beta2, termed Kap104p, has also been described and proposed to play a role in the nuclear import of a yeast hnRNP-like protein termed Nab2p. Here, we define a Nab2p sequence that binds to Kap104p and that functions as an NLS in both human and yeast cells despite lacking any evident similarity to basic or M9 NLSs. Using an in vitro nuclear import assay, we demonstrate that Kap104p can direct the import into isolated human cell nuclei of a substrate containing a wild-type, but not a defective mutant, Nab2p NLS. In contrast, other NLSs, including the M9 NLS, could not function as substrates for Kap104p. Surprisingly, this in vitro assay also revealed that human karyopherin beta1, but not the Kap104p homolog karyopherin beta2, could direct the efficient nuclear import of a Nab2p NLS substrate in vitro in the absence of karyopherin alpha. These data therefore identify a novel NLS sequence, active in both yeast and mammalian cells, that is functionally distinct from both basic and M9 NLS sequences.

Amino Acid Sequence↗
PubMed1994

Competition between nuclear localization and secretory signals determines the subcellular fate of a single CUG-initiated form of FGF3.

The presumed open reading frame for mouse FGF3, starting at the most 5' AUG codon, predicts a hydrophobic N-terminus characteristic of a signal peptide for secretion. However, in reticulocyte lysates and transfected COS-1 cells, the full-length Fgf-3 cDNA is translated almost exclusively from an upstream CUG codon. The resultant products are distributed in both the nucleus and the secretory pathway, implying that the single CUG-initiated form of FGF3 has dual fates. By analysing a series of deletion and replacement mutants and by linking parts of FGF3 to a heterologous protein, we show that secretion is mediated by cleavage adjacent to the previously defined signal peptide, whereas nuclear localization is determined primarily by a classical but relatively weak bipartite motif. In the context of FGF3, nuclear localization also requires the N-terminal sequences which lie upstream of the signal peptide. Thus, the subcellular fate of FGF3 is determined by the competing effects of signals for secretion and nuclear localization within the same protein, rather than by alternative initiation or processing.

Amino Acid Sequence↗
PubMed2002

Role of prodomain in importin-mediated nuclear localization and activation of caspase-2.

Caspase-2 is unique among mammalian caspases because it localizes to the nucleus in a prodomain-dependent manner. The caspase-2 prodomain also regulates caspase-2 activity via a caspase recruitment domain that mediates oligomerization of procaspase-2 molecules and their subsequent autoactivation. In this study we sought to map specific functional regions in the caspase-2 prodomain that regulate its nuclear transport and also its activation. Our data indicate that caspase-2 contains a classical nuclear localization signal (NLS) at the C terminus of the prodomain which is recognized by the importin alpha/beta heterodimer. The mutation of a conserved Lys residue in the NLS abolishes nuclear localization of caspase-2 and binding to the importin alpha/beta heterodimer. Although caspase-2 is imported into the nucleus, mutants lacking the NLS were still capable of inducing apoptosis upon overexpression in transfected cells. We define a region in the prodomain that regulates the ability of caspase-2 to form dot- and filament-like structures when ectopically expressed, which in turn promotes cell killing. Our data provides a mechanism for caspase-2 nuclear import and demonstrate that association of procaspase-2 into higher order structures, rather than its nuclear localization, is required for caspase-2 activation and its ability to induce apoptosis.

3T3 Cells↗
PubMed2004

A novel nuclear localization signal in the human single-minded proteins SIM1 and SIM2.

Human Single-minded 1 (SIM1) and SIM2 genes were found as homologs of Drosophila sim gene which plays a key role in the midline cell lineage of the central nervous system. SIM proteins belong to a family of transcription factors, called bHLH/PAS. Here we examined the intracellular localization of SIM proteins using the expression constructs of whole SIM2 or SIM1 protein fused with enhanced green fluorescent protein (EGFP). The transient expression analysis revealed the nuclear localization of SIM proteins in the cultured cells. To identify the nuclear localization signal, we made expression constructs of EGFP-fusion protein consisting of various portions of SIM proteins. Transfection assay showed the presence of NLS activity in the small region of 23 and 21 amino acid residues at the central part of SIM2 and SIM1 proteins, respectively. Further analysis with amino acid substitution of this small region of SIM2 protein revealed the critical role of five amino acid residues (Arg367, Lys373, Pro385, Tyr386, and Gln389) in NLS activity. The consensus sequence of RKxxKx[K/R]xxxxKxKxRxxPY was estimated as a presumptive NLS in SIM proteins from various species. Thus, the NLS consisting of a cluster of basic amino acids with Pro and Tyr at the C-terminal end is novel and well conserved in the SIM proteins during evolution.

Amino Acid Motifs↗
PubMed2004

Characterization of a nuclear localization signal in the C-terminus of the adeno-associated virus Rep68/78 proteins.

Adeno-associated virus (AAV) replicates in the nucleus of infected cells, and therefore multiple nuclear import events are required for productive infection. We analyzed nuclear import of the viral Rep proteins and characterized a nuclear localization signal (NLS) in the C-terminus. We demonstrate that basic residues in this region constitute an NLS that is transferable and mediates interaction with the nuclear import receptor importin alpha in vitro. Mutant Rep proteins are predominantly cytoplasmic and are severely compromised for interactions with importin alpha, but retain their enzymatic functions in vitro. Interestingly, mutations of the NLS had significantly less effect on importin alpha interaction and replication in the context of Rep78 than when incorporated into the Rep68 protein. Together, our results demonstrate that a bipartite NLS exists in the shared part of Rep68 and Rep78, and suggest that an alternate entry mechanism may also contribute to nuclear localization of the Rep78 protein.

Cell Line↗
PubMed2005

Nuclear localization of the Nipah virus W protein allows for inhibition of both virus- and toll-like receptor 3-triggered signaling pathways.

The Nipah virus V and W proteins, which are encoded by the P gene via RNA editing, have a common N-terminal domain but unique C-terminal domains. They localize to the cytoplasm and nucleus, respectively, and have both been shown to function as inhibitors of JAK/STAT signaling. Here we report that V and W proteins also block virus activation of the beta interferon (IFN-beta) promoter and the IFN regulatory factor 3 (IRF3)-responsive IFN-stimulated gene 54 promoter. Surprisingly, only W protein shows strong inhibition of promoter activation in response to stimulation of Toll-like receptor 3 (TLR3) by extracellular double-stranded RNA. This activity is dependent on the nuclear localization of W protein. Within the unique C-terminal domain of W protein, we have identified a nuclear localization signal (NLS) that requires basic residues at positions 439, 440, and 442. This NLS is responsible for mediating the preferential interaction of W protein with karyopherin-alpha 3 and karyopherin-alpha 4. Nuclear localization of W protein therefore enables it to target both virus and TLR3 pathways, whereas the cytoplasmic V protein is restricted to inhibiting the virus pathway. We propose that this discrepancy is in part due to the V protein being less able to block signaling in response to the kinase, TBK-1, whereas both V and W can prevent promoter activation in response to IKKepsilon. We demonstrate that, when the TLR3 pathway is stimulated, the levels of phosphorylated IRF3 are reduced in the presence of W protein but not V protein, confirming the differential effects of these proteins and illustrating that W protein-mediated inhibition is due to a loss of active IRF3.

Amino Acid Sequence↗
PubMed1997

Induction of S-phase entry by E2F transcription factors depends on their nuclear localization.

The E2F transcription factors are essential for regulating the correct timing of activation of several genes whose products are implicated in cell proliferation and DNA replication. The E2Fs are targets for negative regulation by the retinoblastoma protein family, which includes pRB, p107, and p130, and they are in a pathway that is frequently found altered in human cancers. There are five members of the E2F family, and they can be divided into two functional subgroups. Whereas, upon overexpression, E2F-1, -2, and -3 induce S phase in quiescent fibroblasts and override G1 arrests mediated by the p16INK4A tumor suppressor protein or neutralizing antibodies to cyclin D1, E2F-4 and -5 do not. Using E2F-1 and E2F-4 as representatives of the two subgroups, we showed here, by constructing a set of chimeric proteins, that the amino terminus of E2F-1 is sufficient to confer S-phase-inducing potential as well as the ability to efficiently transactivate an E2F-responsive promoter to E2F-4. We found that the E2F-1 amino terminus directs chimeric proteins to the nucleus. Surprisingly, a short nuclear localization signal derived from simian virus 40 large T antigen could perfectly substitute for the presence of the E2F-1 amino terminus in these assays. Thus, nuclearly localized E2F-4, when overexpressed, displayed biological activities similar to those of E2F-1. Furthermore, we showed that nuclear localization of endogenous E2F-4 is cell cycle regulated, with E2F-4 being nuclear in the G0 and early G1 phases and mainly cytoplasmic after the pRB family members have become phosphorylated. We propose a novel mechanism for the regulation of E2F-dependent transcription in which E2F-4 regulates transcription only from G0 until mid- to late G1 phase whereas E2F-1 is active in late G1 and S phases, until it is inactivated by cyclin A-dependent kinase in late S phase.

Animals↗
PubMed2006

A novel nuclear-localized protein with special adenylate kinase properties from Caenorhabditis elegans.

The adrenal gland protein AD-004 like protein (ADLP) from Caenorhabditis elegans was cloned and expressed in Escherichia coli. Enzyme assays showed that ADLP has special adenylate kinase (AK) properties, with ATP and dATP as the preferred phosphate donors. In contrast to all other AK isoforms, AMP and dAMP were the preferred substrates of ADLP; CMP, TMP and shikimate acid were also good substrates. Subcellular localization studies showed a predominant nuclear localization for this protein, which is different from AK1-AK5, but similar to that of human AK6. These results suggest that ADLP is more likely a member of the AK6 family. Furthermore, RNAi experiments targeting ADLP were conducted and showed that RNAi treatment resulted in the suppression of worm growth.

Adenylate Kinase↗
PubMedDate not supplied

Coupling of nuclear localization signals to plasmid DNA and specific interaction of the conjugates with importin alpha.

The nuclear localization signal (NLS) of the SV40 large T antigen efficiently induces nuclear targeting of proteins. We have developed a chemical strategy for covalent coupling of NLS peptides to plasmid DNA. A p-azido-tetrafluoro-benzyl-NLS peptide conjugate was synthesized. This conjugate was used to covalently associate NLS peptides to plasmid DNA by photoactivation. Reporter gene was expressed after transfection of the plasmid-NLS conjugates in NIH 3T3 cells. The conjugates interacted specifically with the NLS-receptor importin alpha, but plasmid-NLS conjugates were not detected in the nucleus, by fluorescence microscopy, after cytoplasmic microinjection.

3T3 Cells↗
PubMed2005

Insertion/deletion polymorphism in the BRCA2 nuclear localization signal.

Mutations in human BRCA2 confer an increased risk of female breast cancer. In this study, we found a novel insertion/deletion polymorphism (10204insAAA causing amino acid change M3332IK) in canine BRCA2, which is located in the putative second nuclear localization signal (NLS2) and C-terminal Rad51-binding region. The nuclear localization of the insAAA C-terminus was more efficient than localization of the delAAA sequence when NLS1 was mutated. Strong, comparable Rad51 binding was observed for both the insAAA and delAAA C-termini. Dogs with the insertion/deletion polymorphism will provide a new model for studying the function of BRCA2.

Alleles↗
PubMed2001

Nuclear localization signals in the Xenopus FGF embryonic early response 1 protein.

Xenopus early response 1 (XER1) is a fibroblast growth factor-inducible transcription factor whose developmentally regulated nuclear localization is thought to be important in the control of cell differentation during embryonic development [Luchman et al., Mech. Dev. 80 (1999) 111-114]. Analysis of the XER1 amino acid sequence revealed four regions which contain potential nuclear localization sequences (NLSs). Using mutant XER1 proteins and portions of XER1 fused to green fluorescent protein (GFP) transfected into NIH 3T3 cells, we have determined that only one of these, NLS4, located near the carboxy-terminus of XER1, is necessary and sufficient for targeting exclusively to the nucleus. Of the other three predicted NLS sequences, only NLS1, consisting of the sequence (138)RPRRCK(143) was shown to function as a cryptic, weak NLS. NLS4 contains a core region consisting of the sequence (463)RPIKRQRMD(471) which is similar to the core NLS directing the human c-MYC protein to the nucleus. The core sequence is flanked by a predicted cdc2/protein kinase A phosphorylation motif, however mutation of the serine(472) to alanine or aspartic acid had no detectable effect on accumulation of GFP-XER1 fusion proteins in the nucleus, demonstrating that this putative phosphorylation site plays no role in regulating nuclear transport.

3T3 Cells↗
PubMed2006

Identification of a nuclear localization signal in the retinitis pigmentosa-mutated RP26 protein, ceramide kinase-like protein.

Retinitis pigmentosa (RP) is a genetically heterogeneous disease characterized by degeneration of the retina. A mutation in a new ceramide kinase (CERK) homologous gene, named CERK-like protein (CERKL), was found to cause autosomal recessive retinitis pigmentosa (RP26). Here, we show a point mutation of one of two putative nuclear localization signal (NLS) sequences inhibited the nuclear localization of the protein. Furthermore, the tetra-GFP-tagged NLS, which cannot passively enter the nucleus, was observed not only in the nucleus but also in the nucleolus. Our results provide the first evidence of the active nuclear import of CERKL and suggest that the identified NLS might be responsible for nucleolar retention of the protein. As recent studies have shown other RP-related proteins are localized in the nucleus or the nucleolus, our identification of NLS in CERKL suggests that CERKL likely plays important roles for retinal functions in the nucleus and the nucleolus.

Active Transport, Cell Nucleus↗
PubMed1999

Nuclear localization of human immunodeficiency virus type 1 integrase expressed as a fusion protein with green fluorescent protein.

Lentiviruses in general and the human immunodeficiency virus type 1 (HIV-1) in particular have the ability to integrate their genome stably into the chromosome of nondividing cells. Integration of HIV cDNA is mediated by the viral integrase (IN). Apart from its catalytic activity, this enzyme seems to play an important role in the transport of the HIV preintegration complex into the nucleus of nondividing cells. We studied the karyophilic properties of IN by constructing an N-terminal fusion protein of HIV-1 integrase and green fluorescent protein (GFP-IN). Transient expression of GFP-IN in various mammalian cell lines was demonstrated by fluorescence microscopy, flow cytometry, and Western blotting. Although wild-type GFP was localized throughout the cell, GFP-IN was localized predominantly in the nucleus. Nuclear localization of GFP-IN was also obtained after transient transfection of the cells arrested in the G1/S phase of the cell cycle. These results provide compelling evidence for the karyophilic properties of the HIV-1 integrase.

Cell Division↗
PubMed2004

Human heparanase nuclear localization and enzymatic activity.

In previous studies, we have demonstrated that human heparanase (endo-beta-D-glucuronidase) is localized primarily in a perinuclear pattern within lysosomes and late endosomes, and occasionally may be surface associated and secreted. The presence of two potential nuclear localization sequences in human heparanase, led us to investigate heparanase translocation into the nucleus and subsequent degradation of nuclear heparan sulfate. Applying cell fractionation, Western blot analysis, determination of heparanase activity and confocal microscopy, we identified heparanase within the nuclei of human glioma and breast carcinoma cells and estimated its amount to be about 7% of the cytosolic enzyme. Our results indicate that nuclear heparanase colocalizes with nuclear heparan sulfate and is enzymaticaly active. Moreover, following uptake of latent 65 kDa heparanase by cells that do not express the enzyme, an active 50 kDa heparanase was detected in the cell nucleus, capable of degrading both nuclear and extracellular matrix-derived heparan sulfate. Immunohistochemical examination of human squamous cell carcinoma specimens revealed a prominent granular staining of heparanase within the nuclei of the epithelial tumor cells vs no nuclear staining in the adjacent stromal cells. Taken together, it appears that heparanase is translocated into the cell nucleus where it may degrade the nuclear heparan sulfate and thereby affect nuclear functions that are thought to be regulated by heparan sulfate. Nuclear localization of heparanase suggests that the enzyme may fulfill nontraditional functions (ie, regulation of gene expression and signal transduction) apart of its well-documented involvement in cancer metastasis, angiogenesis and inflammation.

Active Transport, Cell Nucleus↗
PubMed2000

Zn finger and nuclear localization of transcription factor Sp1.

Transcription factor Sp1 is located in the nucleus of a mammalian cell and importantly related to expression of many cellular genes. In order to elucidate the nuclear localization mechanism of Sp1, various truncated fragments of Sp1 were fused to green fluorescent protein (GFP) and expressed in HeLa cell. The results show significance of the DNA binding region, especially, zinc finger (Zn finger) domain for nuclear localization of Sp1 in HeLa cell.

Binding Sites↗
PubMed2007

Bipartite nuclear localization signal of matrin 3 is essential for vertebrate cells.

Matrin 3, a nuclear matrix protein has potential (1) to withhold promiscuously edited RNAs within the nucleus in cooperation with p54(nrb) and PSF, (2) to mediate NMDA-induced neuronal death, and (3) to modulate promoter activity of genes proximal to matrix/scaffold attachment region (MAR/SAR). We identified a bipartite nuclear localization signal (NLS) of chicken matrin 3 (cmatr3) at residues 583-602. By expressing green fluorescent protein (GFP) fused to the NLS mutant in chicken DT40 cells, we showed an essential role of the NLS for cell proliferation. Furthermore, we showed that both clusters of basic amino acids and a linker of the bipartite NLS were essential and sufficient for the nuclear import of GFP. Exogenous cmatr3 rescued the HeLa cells where human matrin 3 was suppressed by RNA interference, but cmatr3 containing deletions at either of the basic amino acid clusters or the linker could not.

Active Transport, Cell Nucleus↗
PubMed1992

Characterization of a novel nuclear localization signal in the HTLV-I tax transactivator protein.

The Tax trans-activator protein of the type I human T-cell leukemia virus is expressed predominantly in the nuclei of cells. However, this viral trans-activator is distinguished from most other nuclear proteins by the absence of a short highly basic nuclear localization signal. Previous mutational analyses of the tax gene revealed that many of the missense mutations involving the amino terminus of Tax resulted in a predominantly cytoplasmic pattern of expression. We now report that the amino terminal 48 residues of Tax comprise a functional nuclear localization signal as demonstrated by the ability of this region to retarget expression of a large cytoplasmic protein to the nucleus.

Amino Acid Sequence↗