PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “Nuclear Localization Signals”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

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

At least 379 records · Page 21Linked to original sources
PubMed2004

Dual role of the adenovirus pVI C terminus as a nuclear localization signal and activator of the viral protease.

Adenain, the protease produced by adenovirus, is regulated by formation of a heterodimer with an 11 aa peptide derived from the C terminus of another adenoviral protein, pVI. Here, the role of the basic motif KRRR, which is conserved in pVI sequences from human adenovirus serotypes, was investigated. It was shown that this motif is less important than the N- or C-terminal regions in the formation of the adenain-peptide heterodimer and in the activity of the subsequent complex. This motif, however, acted as a nuclear localization signal that was capable of targeting heterologous proteins to the nucleus, resulting in a distinctive intranuclear distribution consisting of discrete foci, which is similar to that found for pVI during adenovirus infection.

Adenoviruses, Human↗
PubMed1994

The maize abscisic acid-responsive protein Rab17 is located in the nucleus and interacts with nuclear localization signals.

The maize abscisic acid (ABA)-responsive rab17 mRNA and Rab17 protein distribution in maize embryo tissues was investigated by in situ hybridization and immunocytochemistry. rab17 mRNA and Rab17 protein were found in all cells of embryo tissues. Synthesis of rab17 mRNA occurred initially in the embryo axis. As maturation progressed, rab17 mRNA was detectable in the scutellum and accumulated in axis cells and provascular tissues. However, the response to exogenous ABA differed in various embryo cell types. The Rab17 protein was located in the nucleus and in the cytoplasm, and qualitative differences in the phosphorylation states of the protein were found between the two subcellular compartments. Based on the similar domain arrangements of Rab17 and a nuclear localization signal (NLS) binding phosphoprotein, Nopp140, interaction of Rab17 with NLS peptides was studied. We found specific binding of Rab17 to the wild-type NLS of the SV40 T antigen but not to an import incompetent mutant peptide. Moreover, binding of the NLS peptide to Rab17 was found to be dependent upon phosphorylation. These results suggest that Rab17 may play a role in nuclear protein transport.

Abscisic Acid↗
PubMed1998

Isolation and characterization of a human gene containing a nuclear localization signal from the critical region for velo-cardio-facial syndrome on 22q11.

Velo-cardio-facial syndrome (VCFS) and DiGeorge syndrome are congenital disorders characterized by craniofacial anomalies, conotruncal heart defects, immune deficiencies, and learning disabilities. Both diseases are associated with similar hemizygous 22q11 deletions, indicating that haploinsufficiency of a gene(s) in 22q11 is responsible for their etiology. We describe here a new gene called NLVCF, which maps to the critical region for VCFS on 22q11 between the genes HIRA and UFD1L. NLVCF encodes a putative protein of 206 amino acids. The coding region encompasses four exons that span a genomic interval of 3.4 kb. Coding sequence analysis revealed that NLVCF is a novel gene that contains two consensus sequences for nuclear localization signals. The Nlvcf mouse homolog is 75% identical in amino acid sequence and maps to the orthologous region on mouse chromosome 16. The human NLVCF transcript is 1.3 kb in size and is expressed at varying levels in many fetal and adult tissues. Whole-mount in situ hybridization showed that Nlvcf is expressed in most structures of 9.5-dpc mouse embryos, with especially high expression in the head as well as in the first and second pharyngeal arches. NLVCF and HIRA are divergently transcribed, and their start codons lie approximately 1 kb apart in both humans and mice. Interestingly, the two genes exhibit a similar expression pattern in mouse embryos, suggesting that they may share common regulatory elements. The pattern of expression of NLVCF and its localization in the critical region suggest that NLVCF may contribute to the etiology of VCFS.

Amino Acid Sequence↗
PubMed2005

Repressor domain and nuclear localization signal of the murine Hoxa-11 protein are located in the homeodomain: no evidence for role of poly alanine stretches in transcriptional repression.

Hoxa-11 is a member of the homeodomain class of transcription factors, which play important roles in metazoan development. Hoxa-11 is particularly interesting because it is involved in a major mammalian innovation, uterus development and gestation. We are interested in the molecular changes underlying this evolutionary innovation. Although phenotypes resulting from loss of functions are well investigated (e.g., female sterility), little is known about the domains contributing to Hoxa-11 protein function. We therefore mapped the domains mediating two essential transcription factor functions, nuclear localization and transcriptional activity in the mouse Hoxa-11 protein. Our results show that the mammal-specific alanine repeat does not contribute to repressor activity, as has been hypothesized based on amino acid composition and analogy with other repressor domains. Interestingly, both the repressor domain as well as the nuclear localization signal (NLS) are located within the homeodomain, adding to the growing evidence that the homeodomain is a multifunctional domain which fulfills essential transcription factor functions beyond DNA binding. It is proposed that the high degree of conservation of the homeodomain is due to the multiple functional constraints that result from the various conserved functions accommodated in the homeodomain.

Alanine↗
PubMed2000

Calcium/calmodulin-dependent protein kinase II containing a nuclear localizing signal is altered in retinal neurons exposed to N-methyl-D-aspartate.

This study investigated N-methyl-D-aspartate (NMDA) mediated cell death and its possible regulation by calcium/calmodulin-dependent protein kinase II (CaMKII) in the adult rat retina. To investigate cell death, the terminal deoxyribonucleotidyltransferase (TdT)-mediated biotin-16-dUTP nick-end labelling (TUNEL) method was used to detect fragmented DNA in fixed tissue sections of rat retina. The TUNEL assay confirmed that apoptosis occurs in the inner nuclear layer (INL) and ganglion cell layer (GCL) following NMDA injection. The level of antibody binding to CaMKII-alpha, the activity of CaMKII, and the mRNA level for the alpha(B) subunit of CaMKII were found to be elevated for short time periods (30 min, 2 h) after a single intravitreal injection of NMDA. In contrast to this, there was a decrease in CaMKII activity and in the CaMKII-alpha(B) mRNA levels at longer time periods (24 h) following injection of NMDA. These effects were specific for the mRNA for the alpha(B) subunit, an alternatively spliced product of the CaMKII-alpha gene, that contains a nuclear localizing signal (NLS) known to target this protein to the nucleus. It is suggested that regulated expression of CaMKII-alpha(B) could be involved in the NMDA-mediated cell death in retinal neurons.

Animals↗
PubMed2005

Processivity factor of KSHV contains a nuclear localization signal and binding domains for transporting viral DNA polymerase into the nucleus.

Kaposi's sarcoma-associated human herpesvirus (KSHV) encodes a processivity factor (PF-8, ORF59) that forms homodimers and binds to viral DNA polymerase (Pol-8, ORF9). PF-8 is essential for stabilizing Pol-8 on template DNA so that Pol-8 can incorporate nucleotides continuously. Here, the intracellular interaction of these two viral proteins was examined by confocal immunofluorescence microscopy. When individually expressed, PF-8 was observed exclusively in the nucleus, whereas Pol-8 was found only in the cytoplasm. However, when co-expressed, Pol-8 was co-translocated with PF-8 into the nucleus. Mutational analysis revealed that PF-8 contains a nuclear localization signal (NLS) as well as domains located at the N-terminus and the C-proximal regions that are required for Pol-8 binding. This study suggests that the mechanism that enables PF-8 to transport Pol-8 into the nucleus is the first critical step required for Pol-8 and PF-8 to function processively in KSHV DNA synthesis.

Amino Acid Sequence↗
PubMed1997

Two potent nuclear localization signals in the gut-enriched Krüppel-like factor define a subfamily of closely related Krüppel proteins.

The gut-enriched Krüppel-like factor (GKLF) is a newly identified transcription factor that contains three C2H2 Krüppel-type zinc fingers. Previous immunocytochemical studies indicate that GKLF is exclusively localized to the nucleus. To identify the nuclear localization signal (NLS) within GKLF, cDNA constructs with various deletions in the coding region of GKLF were generated and analyzed by indirect immunofluorescence in transfected COS-1 cells. In addition, constructs fusing regions representing putative NLSs of GKLF to green fluorescent protein (GFP) were generated and examined by fluorescence microscopy in similarly transfected cells. The results indicate that GKLF contains two potent, independent NLSs: one within the zinc fingers and the other in a cluster of basic amino acids (called 5' basic region) immediately preceding the first zinc finger. In comparison, putative NLSs within the zinc fingers and the 5' basic region of a related Krüppel protein, zif268/Egr-1, are relatively less efficient in their ability to translocate GFP into the nucleus. A search in the protein sequence data base revealed that despite the existence of numerous Krüppel proteins, only two, the lung Krüppel-like factor (LKLF) and the erythroid Krüppel-like factor (EKLF), exhibit similar NLSs to those of GKLF. These findings indicate that GKLF, LKLF, and EKLF are members of a subfamily of closely related Krüppel proteins.

Amino Acid Sequence↗
PubMed1996

The cytostatic function of c-Abl is controlled by multiple nuclear localization signals and requires the p53 and Rb tumor suppressor gene products.

c-Abl is a non-receptor protein-tyrosine kinase lacking a clear physiological role. A clue to its normal function is suggested by overexpression of Abl in fibroblasts, which leads to inhibition of cell growth. This effect requires tyrosine kinase activity and the Abl C-terminus. c-Abl is localized to the cell nucleus, where it can bind DNA, and interacts with the retinoblastoma protein, a potential mediator of the growth-inhibitory effect. Nuclear localization of Abl can be directed by a pentalysine nuclear localization signal in the Abl C-terminus. Here, we have identified two additional basic motifs in the Abl C-terminus, either of which can function independently of the pentalysine signal to localize Abl to the nucleus. Using a quantitative transfection assay, we show that both c-Abl and transforming Abl proteins inhibit entry into S phase and this effect is absolutely dependent on nuclear localization. Further, we demonstrate that the Abl cytostatic effect requires both the Rb and p53 tumor suppressor gene products. These results indicate that Abl inhibits cell proliferation by interacting with central elements of the cell cycle control apparatus in the nucleus, and suggest a direct connection between p53 and Rb in this growth-inhibitory pathway.

3T3 Cells↗
PubMed2000

Two novel proteins, PopB, which has functional nuclear localization signals, and PopC, which has a large leucine-rich repeat domain, are secreted through the hrp-secretion apparatus of Ralstonia solanacearum.

The Ralstonia solanacearum hrp gene cluster codes for components of a type III secretion pathway necessary for the secretion of PopA1, a hypersensitive response-like elicitor protein. In the present study, we show that several other Hrp-secreted proteins can be detected by growing wild-type bacteria in minimal medium in the presence of Congo red. Two of these proteins, PopB and PopC, are encoded by genes located downstream of popA and constitute an operon with popA. popABC mutants retain the wild-type ability to cause disease in hosts and to elicit the hypersensitive response on non-hosts. Expression of the popABC operon is controlled by the hrpB regulatory gene and is induced upon co-culture with Arabidopsis cell suspensions. This plant cell-specific induction depends on PrhA, a putative receptor for plant specific signal(s). The transcription of the popABC operon is not modified by the addition of Congo red to the growth medium and the intracellular pools of PopB and PopC are very similar in the absence or presence of Congo red. Preliminary data suggest that Congo red stabilizes secreted proteins in the extracellular medium. PopB is a 173-amino-acid-basic protein that contains a functional bipartite nuclear localization signal. PopC is a 1024-amino-acid protein that carries 22 tandem leucine-rich repeats (LRR). The LRR domain of this protein forms a consensus that perfectly matches the predicted eukaryotic cytoplasmic LRR consensus. We propose that PopB and PopC may be translocated into plant cells via the Hrp pathway.

Amino Acid Motifs↗
PubMed1994

Nuclear localization signals in the core protein of hepatitis C virus.

The core protein of the hepatitis C virus is derived from the N-terminal 191 amino acids of the viral polyprotein by proteolytic cleavage. In the current study, subcellular localizations of the HCV core and its beta-galactosidase fusion proteins in transfected cells were examined by indirect immunofluorescence and cytochemical staining. The core protein was located predominantly in the cytoplasm 6 days after a plasmid encoding the full-length core protein had been introduced into mammalian cells. A hydrophobic domain in the C-terminal region of the core protein may block the efficiency of nuclear transport, since a beta-galactosidase fusion protein that contains HCV core protein lacking the C-terminal 66-amino-acid was located within the nuclei of mammalian cells 24 hours posttransfection. Three independent nuclear localization signals were further identified in the N-terminal region of the HCV core protein.

Animals↗
PubMed2005

Regulation of phytochrome B nuclear localization through light-dependent unmasking of nuclear-localization signals.

Phytochromes are red and far-red photoreceptors that regulate plant growth and development in response to environmental light cues. Phytochromes exist in two photo-interconvertible conformational states: an inactive Pr form and an active Pfr form. The alteration of phytochromes' subcellular location functions as a major regulatory mechanism of their biological activities. Whereas phytochromes in the Pr form localize in the cytoplasm, phytochromes in the Pfr form accumulate in the nucleus, where they interact with transcription factors to regulate gene expression. The molecular details of the regulation of phytochrome translocation by light are poorly understood. Using Arabidopsis phyB as a model, we demonstrate that the C-terminal PAS-related domain (PRD) is both necessary and sufficient for phyB nuclear import and that the entire C terminus is required for nuclear-body (NB) localization. We also show that phyB's N-terminal bilin lyase domain (BLD) and PHY domain interact directly with the PRD in a light-dependent manner. In vivo localization studies indicate that BLD-PHY is sufficient to regulate phyB's nuclear accumulation. For phyB nuclear localization, our results suggest a molecular mechanism in which the nuclear-localization signal in the PRD is masked by interactions with phyB's chromophore-attachment domains and unmasked by light-dependent conformational changes.

Arabidopsis↗
PubMed2000

Identification of two novel zinc finger modules and nuclear localization signal in rat spermatidal protein TP2 by site-directed mutagenesis.

Spermatidal protein TP2, which appears transiently during stages 12-16 of mammalian spermiogenesis, is a DNA condensing zinc metalloprotein with a preference to GC-rich DNA. We have carried out a detailed site-directed mutagenesis analysis of rat spermatidal protein TP2 to delineate the amino acid residues involved in coordination with two atoms of zinc. Two zinc fingers modules have been identified involving 4 histidine and 4 cysteine residues, respectively. The modular structure of the two zinc fingers identified in TP2 define a new class of zinc finger proteins that do not fall into any of the known classes of zinc fingers. Transfection experiments with COS-7 cells using wild type and the two zinc finger pocket mutants have shown that TP2 preferentially localizes to nucleolus. The nuclear localization signal in TP2 was identified to be (87)GKVSKRKAV(95) present in the C-terminal third of TP2 as a part of an extended NoLS sequence.

Amino Acid Sequence↗
PubMed1991

The functionally active IE2 immediate-early regulatory protein of human cytomegalovirus is an 80-kilodalton polypeptide that contains two distinct activator domains and a duplicated nuclear localization signal.

The IE2 region of the human cytomegalovirus (CMV) strain Towne major immediate-early (MIE) gene encodes a transcriptional transactivator that stimulates expression from a variety of heterologous target promoters but specifically down-regulates its own promoter. By immunofluorescence and Western immunoblot analysis with monospecific peptide antisera, we found that human CMV MIE exon 5 encodes four overlapping polypeptides, two present at immediate-early times (80 and 55 kDa) and two others detected only at late times after infection (55 and 40 kDa). However, only the 80-kDa version (579 amino acids), which is derived from the small upstream exons 2 and 3 fused to the intact exon 5 region, was functionally active in both transactivation and autoregulation as assessed by cotransfection experiments. These results confirm the corrected assignment of the coding capacity of the exon 5 region based on amino acid homology with the equivalent IE2 protein from simian CMV (Colburn). In transient DNA transfection assays, IE2 expression plasmids also produced a predominant full-length 80-kDa protein, which was localized in a distinctive reticular pattern in the nucleus. Two short basic nuclear localization signals in IE2 were identified by deletion analysis and by conversion of a test cytoplasmic herpes simplex virus protein into a form that localized in the nucleus after insertion of either of these two human CMV motifs. Functional assays with MIE region plasmids containing deletions or truncations in exon 5 revealed that both transactivation and autoregulation required several distinct domains within the COOH half of the IE2 protein, whereas a region between codons 99 and 194 could be discarded. Three segments at the NH2 end of the protein between codons 1 to 85, 86 to 98, and 195 to 290 were also essential for transactivation but played no role in autoregulation. Finally, in domain swap experiments, GAL4-fusion proteins containing either an NH2-terminal 51-amino-acid domain from exon 3 (codons 25 to 85) or the COOH-terminal 33-amino-acid domain from exon 5 (codons 544 to 579) identified two distinct activator domains from IE2, both of which have acidic characteristics.

Amino Acid Sequence↗
PubMed1999

Definition of a major p53 binding site on Ad2E1B58K protein and a possible nuclear localization signal on the Ad12E1B54K protein.

Previous studies have established that adenovirus 2/5 early region 1B (Ad E1B) 58K protein binds p53 strongly and co-localizes with it to cytoplasmic dense bodies whilst the homologous Ad12E1B54K protein binds only weakly and co-localizes primarily to the nucleus in Ad12E1 transformed cells. We have used these properties of the E1B proteins from different viral serotypes to map the p53 binding site on the Ad2/5 protein. A set of chimaeric genes was constructed containing different proportions of the Ad12 and Ad2E1B DNA. These, together with Ad12E1A and E1B19K DNA, were transfected into baby rat kidney cells and transformed lines isolated. From an examination of the properties of these Ad12/Ad2E1B fusion proteins in co-immunoprecipitation and subcellular localization experiments it has been concluded that the p53 binding site on Ad2E1B58K protein lies between amino acids 216 and 235 and that the homologous region on Ad12E1B54K protein also binds p53. In addition, a unique nuclear localization signal is located on Ad12E1B54K between residues 228 and 239. We suggest that primary structure differences in these regions of the Ad2 and Ad12E1B proteins are responsible for the different subcellular localizations in AdE1 transformants.

Adenoviridae↗
PubMed2002

Identification of the nuclear localization signal of p21(cip1) and consequences of its mutation on cell proliferation.

Overexpression of p21(cip1) induces cell cycle arrest. Although this ability has been correlated with its nuclear localization, the evidence is not conclusive. The mutants that were used to inhibit its nuclear translocation could no longer bind to several proteins known to interact with the last 25 amino acids of p21(cip1). Here we used point mutation analysis and fusion of the proteins to DsRed to identify which amino acids are essential for the nuclear localization of p21(cip1). We conclude that amino acids RKR(140-142) are essential for nuclear translocation of p21(cip1). While wild-type DsRed-p21 induces cell cycle arrest in 95% of transfected cells, overexpression of cytoplasmatic p21AAA(140-142) arrested only 20% of transfected cells. We conclude that cytoplasmatic p21, with no deletion in the C-terminal region, had a much lower capacity to arrest the cell cycle.

3T3 Cells↗
PubMed1987

Pentapeptide nuclear localization signal in adenovirus E1a.

The adenovirus E1a gene products are nuclear proteins important in transcriptional control of viral functions during infection. By producing normal E1a proteins and derivatives of E1a in bacteria and microinjecting these proteins into cultured cells, we were able to examine their ability to localize to the nucleus. We showed that a short peptide sequence at the carboxyl terminus of E1a is necessary for the rapid (30-min) nuclear localization of that protein. Additionally, we showed that just the last five amino acids of E1a are sufficient to direct nuclear accumulation of a heterologous protein, Escherichia coli galactokinase, with the same kinetics as native E1a. The mechanism by which this pentamer mediates rapid nuclear localization was examined by testing the ability of a galactokinase derivative which has no signal pentamer to exit the nucleus, as well as to enter it. Because neither free entry nor exit was detected, the effect of the signal is unlikely to be through increased nuclear retention of freely diffusible proteins but rather by enhancement of entry into the nucleus.

Adenoviridae↗
PubMed1994

Negative charge at the casein kinase II site flanking the nuclear localization signal of the SV40 large T-antigen is mechanistically important for enhanced nuclear import.

Nuclear import of SV40 large T-antigen (T-ag) is completely dependent on the T-ag nuclear localization sequence (amino acids 126-132), but the rate of nuclear import is greatly increased by the additional presence of the N-terminal flanking sequence (amino acids 111-125), which includes a site for casein kinase II (CKII) (Ser111/112). The role of this site was investigated by site-directed mutagenesis and analysis of the effects on phosphorylation and on nuclear import at the single cell level using microinjection and quantitative fluorescent techniques. Removal of the CKII site either by substitution of S111/112 by nonphosphorylatable amino acid residues, or mutation of the Asp-Asp-Glu113/115 CKII recognition sequence to Asn-Asn-Gln, resulted in nuclear import rates less than 4% wild type, demonstrating that the CKII site was responsible for the enhancement of nuclear import conferred by T-ag amino acids 111-125. The substitution of Asp for Ser112, the serine preferentially phosphorylated by purified CKII, enhanced nuclear import to about 45% maximal wild type rates. It is concluded that negative charge at the CKII site, normally provided by phosphorylation, is mechanistically important for nuclear transport enhancement. There was no evidence or a direct role for phosphatases or dephosphorylation in the transport process.

Amino Acid Sequence↗