scholarly journals Role of Nuclear Pools of Aminoacyl-tRNA Synthetases in tRNA Nuclear Export

2001 ◽  
Vol 12 (5) ◽  
pp. 1381-1392 ◽  
Author(s):  
Abul K. Azad ◽  
David R. Stanford ◽  
Srimonti Sarkar ◽  
Anita K. Hopper
Keyword(s):  
Nuclear Localization ◽  
Nuclear Export ◽  
Trna Synthetase ◽  
Nuclear Localization Sequence ◽  
Sequence Alignments ◽  
Trna Aminoacylation ◽  
Trna Synthetases ◽  
Aminoacyl Trna Synthetases ◽  
Localization Sequence ◽  
Nuclear Location

Reports of nuclear tRNA aminoacylation and its role in tRNA nuclear export ( Lund and Dahlberg, 1998 ; Sarkar et al., 1999 ; Grosshans et al., 2000a ) have led to the prediction that there should be nuclear pools of aminoacyl-tRNA synthetases. We report that in budding yeast there are nuclear pools of tyrosyl-tRNA synthetase, Tys1p. By sequence alignments we predicted a Tys1p nuclear localization sequence and showed it to be sufficient for nuclear location of a passenger protein. Mutations of this nuclear localization sequence in endogenous Tys1p reduce nuclear Tys1p pools, indicating that the motif is also important for nucleus location. The mutations do not significantly affect catalytic activity, but they do cause defects in export of tRNAs to the cytosol. Despite export defects, the cells are viable, indicating that nuclear tRNA aminoacylation is not required for all tRNA nuclear export paths. Because the tRNA nuclear exportin, Los1p, is also unessential, we tested whether tRNA aminoacylation and Los1p operate in alternative tRNA nuclear export paths. No genetic interactions between aminoacyl-tRNA synthetases and Los1p were detected, indicating that tRNA nuclear aminoacylation and Los1p operate in the same export pathway or there are more than two pathways for tRNA nuclear export.

scholarly journals Regulation of mRNA export through API5 and nuclear FGF2 interaction

2020 ◽  
Vol 48 (11) ◽  
pp. 6340-6352 ◽  
Author(s):  
Seoung Min Bong ◽  
Seung-Hyun Bae ◽  
Bomin Song ◽  
HyeRan Gwak ◽  
Seung-Won Yang ◽  
...  
Keyword(s):  
Nuclear Localization ◽  
Nuclear Export ◽  
Mrna Export ◽  
Structural Basis ◽  
Nuclear Localization Sequence ◽  
Physical Interaction ◽  
Dynamic Regulation ◽  
Localization Sequence ◽  
Localization Signal ◽  
Apoptosis Inhibitor

Abstract API5 (APoptosis Inhibitor 5) and nuclear FGF2 (Fibroblast Growth Factor 2) are upregulated in various human cancers and are correlated with poor prognosis. Although their physical interaction has been identified, the function related to the resulting complex is unknown. Here, we determined the crystal structure of the API5–FGF2 complex and identified critical residues driving the protein interaction. These findings provided a structural basis for the nuclear localization of the FGF2 isoform lacking a canonical nuclear localization signal and identified a cryptic nuclear localization sequence in FGF2. The interaction between API5 and FGF2 was important for mRNA nuclear export through both the TREX and eIF4E/LRPPRC mRNA export complexes, thus regulating the export of bulk mRNA and specific mRNAs containing eIF4E sensitivity elements, such as c-MYC and cyclin D1. These data show the newly identified molecular function of API5 and nuclear FGF2, and provide a clue to understanding the dynamic regulation of mRNA export.

Relationship between the function and the location of G1 cyclins inS. cerevisiae

2001 ◽  
Vol 114 (24) ◽  
pp. 4599-4611 ◽  
Author(s):  
Nicholas P. Edgington ◽  
Bruce Futcher
Keyword(s):  
Nuclear Localization ◽  
Cellular Localization ◽  
Subcellular Location ◽  
Nuclear Localization Sequence ◽  
Cyclin Dependent Kinase ◽  
Cyclin Dependent Kinases ◽  
G1 Cyclins ◽  
C Terminus ◽  
Localization Sequence ◽  
Nuclear Location

The Saccharomyces cerevisiae cyclin-dependent kinase Cdc28 forms complexes with nine different cyclins to promote cell division. These nine cyclin-Cdc28 complexes have different roles, but share the same catalytic subunit; thus, it is not clear how substrate specificity is achieved. One possible mechanism is specific sub-cellular localization of specific complexes. We investigated the location of two G1 cyclins using fractionation and microscopy. In addition, we developed ‘forced localization’ cassettes, which direct proteins to particular locations, to test the importance of localization. Cln2 was found in both nucleus and cytoplasm. A substrate of Cln2, Sic1, was also in both compartments. Cytoplasmic Cln2 was concentrated at sites of polarized growth. Forced localization showed that some functions of Cln2 required a cytoplasmic location, while other functions required a nuclear location. In addition, one function apparently required shuttling between the two compartments. The G1 cyclin Cln3 required nuclear localization. An autonomous, nuclear localization sequence was found near the C-terminus of Cln3. Our data supports the hypothesis that Cln2 and Cln3 have distinct functions and locations, and the specificity of cyclin-dependent kinases is mediated in part by subcellular location.

Oxidative stress-induced modifications of histidyl-tRNA synthetase affect its tRNA aminoacylation activity but not its immunoreactivity

2011 ◽  
Vol 89 (6) ◽  
pp. 545-553 ◽  
Author(s):  
Sander H.J. van Dooren ◽  
Reinout Raijmakers ◽  
Helma Pluk ◽  
Angelique M.C. Lokate ◽  
Tom S. Koemans ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Cell Death ◽  
Immunological Tolerance ◽  
Trna Synthetase ◽  
Oxidative Modification ◽  
Jurkat Cells ◽  
Tryptophan Residue ◽  
Trna Aminoacylation ◽  
Trna Synthetases ◽  
Aminoacyl Trna Synthetases

The aminoacyl-tRNA synthetases are ubiquitously expressed enzymes that catalyze the esterification of amino acids to their cognate tRNAs. Autoantibodies against several aminoacyl-tRNA synthetases are found in autoimmune polymyositis and dermatomyositis patients. Because necrosis is often found in skeletal muscle biopsies of these patients, we hypothesized that cell-death-induced protein modifications may help in breaking immunological tolerance. Since cell death is associated with oxidative stress, the effect of oxidative stress on the main myositis-specific autoantibody target Jo-1 (histidyl-tRNA synthetase; HisRS) was studied in detail. The exposure of Jurkat cells to hydrogen peroxide resulted in the detection of several oxidized methionines and one oxidized tryptophan residue in the HisRS protein, as demonstrated by mass spectrometry. Unexpectedly, the tRNA aminoacylation activity of HisRS appeared to be increased upon oxidative modification. The analysis of myositis patient sera did not lead to the detection of autoantibodies that are specifically reactive with the modified HisRS protein. The results of this study demonstrate that the Jo-1/HisRS autoantigen is modified under oxidative stress conditions. The consequences of these modifications for the function of HisRS and its autoantigenicity are discussed.

Antagonistic effects of NES and NLS motifs determine S. cerevisiae Rna1p subcellular distribution

1999 ◽  
Vol 112 (3) ◽  
pp. 339-347 ◽  
Author(s):  
W. Feng ◽  
A.L. Benko ◽  
J.H. Lee ◽  
D.R. Stanford ◽  
A.K. Hopper
Keyword(s):  
Nuclear Membrane ◽  
Nuclear Export ◽  
Nuclear Localization Sequence ◽  
Gtpase Activating Protein ◽  
Gtp Hydrolysis ◽  
Nuclear Interior ◽  
Localization Sequence ◽  
Nuclear Location ◽  
Ran Gtp ◽  
Gtpase Ran

Nucleus/cytosol exchange requires a GTPase, Ran. In yeast Rna1p is the GTPase activating protein for Ran (RanGAP) and Prp20p is the Ran GDP/GTP exchange factor (GEF). RanGAP is primarily cytosolic and GEF is nuclear. Their subcellular distributions led to the prediction that Ran-GTP hydrolysis takes place solely in the cytosol and GDP/GTP exchange solely in the nucleus. Current models propose that the Ran-GTP/Ran-GDP gradient across the nuclear membrane determines the direction of exchange. We provide three lines of evidence that Rna1p enters and leaves the nuclear interior. (1) Rna1p possesses leucine-rich nuclear export sequences (NES) that are able to relocate a passenger karyophilic protein to the cytosol; alterations of consensus residues re-establish nuclear location. (2) Rna1p possesses other sequences that function as a novel nuclear localization sequence able to deliver a passenger cytosolic protein to the nucleus. (3) Endogenous Rna1p location is dependent upon Xpo1p/Crm1p, the yeast exportin for leucine-rich NES-containing proteins. The data support the hypothesis that Rna1p exists on both sides of the nuclear membrane, perhaps regulating the Ran-GTP/Ran-GDP gradient, participating in a complete RanGTPase nuclear cycle or serving a novel function.

scholarly journals G Protein-Coupled Receptor Kinase 5 Contains a DNA-Binding Nuclear Localization Sequence

2004 ◽  
Vol 24 (23) ◽  
pp. 10169-10179 ◽  
Author(s):  
Laura R. Johnson ◽  
Mark G. H. Scott ◽  
Julie A. Pitcher
Keyword(s):  
Dna Binding ◽  
G Protein ◽  
Nuclear Localization ◽  
Nuclear Export ◽  
Calcium Ionophore ◽  
Nuclear Localization Sequence ◽  
G Protein Coupled Receptor ◽  
Gpcr Activation ◽  
Localization Sequence ◽  
G Protein Coupled

ABSTRACT G protein-coupled receptor kinases (GRKs) mediate desensitization of agonist-occupied G protein-coupled receptors (GPCRs). Here we report that GRK5 contains a DNA-binding nuclear localization sequence (NLS) and that its nuclear localization is regulated by GPCR activation, results that suggest potential nuclear functions for GRK5. As assessed by fluorescence confocal microscopy, transfected and endogenous GRK5 is present in the nuclei of HEp2 cells. Mutation of basic residues in the catalytic domain of GRK5 (between amino acids 388 and 395) results in the nuclear exclusion of the mutant enzyme (GRK5Δ NLS), demonstrating that GRK5 contains a functional NLS. The nuclear localization of GRK5 is subject to dynamic regulation. Calcium ionophore treatment or activation of Gq-coupled muscarinic-M3 receptors promotes the nuclear export of the kinase in a Ca2+/calmodulin (Ca2+/CaM)-dependent fashion. Ca2+/CaM binding to the N-terminal CaM binding site of GRK5 mediates this effect. Furthermore, GRK5, but not GRK5Δ NLS or GRK2, binds specifically and directly to DNA in vitro. Consistent with their presence in the nuclei of transfected cells, all the GRK4, but not GRK2, subfamily members contain putative NLSs. These results suggest that the GRK4 subfamily of GRKs may play a signaling role in the nucleus and that GRK4 and GRK2 subfamily members perform divergent cellular functions.

scholarly journals Nucleocytoplasmic Shuttling of Pak5 Regulates Its Antiapoptotic Properties

2006 ◽  
Vol 26 (8) ◽  
pp. 3215-3230 ◽  
Author(s):  
Sophie Cotteret ◽  
Jonathan Chernoff
Keyword(s):  
Cell Survival ◽  
Nuclear Localization ◽  
Nuclear Export ◽  
Small Gtpase ◽  
Nuclear Localization Sequence ◽  
Mutant Form ◽  
Leptomycin B ◽  
Localization Sequence ◽  
Activate Cell ◽  
P21 Activated Kinase

ABSTRACT p21-activated kinase 5 (Pak5) is an effector for the small GTPase Cdc42, known to activate cell survival signaling pathways. Previously, we have shown that Pak5 localizes primarily to mitochondria. To study the relationship between Pak5 localization and its effects on apoptosis, we identified three N-terminal regions that regulate the localization of this kinase: a mitochondrial targeting sequence, a nuclear export sequence, and a nuclear localization sequence. When the first two sequences are deleted, Pak5 is retained in the nucleus and no longer protects cells from apoptosis. Moreover, blockade of nuclear export with leptomycin B causes endogenous Pak5 to accumulate in the nucleus. Additionally, the removal of the N-terminal nuclear localization sequence abolishes Pak5 translocation to the nucleus. Finally, we show that reduction of endogenous Pak5 expression in neuroblastoma and neural stem cells increases their sensitivity to apoptosis and that this effect is reversed upon reexpression of wild-type Pak5 but not of a mutant form of Pak5 that cannot localize to mitochondria. These results show that Pak5 shuttles from mitochondria to the nucleus and that the mitochondrial localization of Pak5 is vital to its effects on cell survival.

scholarly journals Loss of IκBα-Mediated Control over Nuclear Import and DNA Binding Enables Oncogenic Activation of c-Rel

1998 ◽  
Vol 18 (9) ◽  
pp. 5445-5456 ◽  
Author(s):  
Shrikesh Sachdev ◽  
Mark Hannink
Keyword(s):  
Dna Binding ◽  
Nuclear Localization ◽  
Nuclear Import ◽  
Nuclear Export ◽  
Specific Inhibitor ◽  
Nuclear Localization Sequence ◽  
Treatment Results ◽  
Leptomycin B ◽  
Localization Sequence ◽  
Nuclear Shuttling

ABSTRACT The IκBα protein is able both to inhibit nuclear import of Rel/NF-κB proteins and to mediate the export of Rel/NF-κB proteins from the nucleus. We now demonstrate that the c-Rel–IκBα complex is stably retained in the cytoplasm in the presence of leptomycin B, a specific inhibitor of Crm1-mediated nuclear export. In contrast, leptomycin B treatment results in the rapid and complete relocalization of the v-Rel–IκBα complex from the cytoplasm to the nucleus. IκBα also mediates the rapid nuclear shuttling of v-Rel in an interspecies heterokaryon assay. Thus, continuous nuclear export is required for cytoplasmic retention of the v-Rel–IκBα complex. Furthermore, although IκBα is able to mask the c-Rel-derived nuclear localization sequence (NLS), IκBα is unable to mask the v-Rel-derived NLS in the context of the v-Rel–IκBα complex. Taken together, our results demonstrate that IκBα is unable to inhibit nuclear import of v-Rel. We have identified two amino acid differences between c-Rel and v-Rel (Y286S and L302P) which link the failure of IκBα to inhibit nuclear import and DNA binding of a mutant c-Rel protein to oncogenesis. Our results support a model in which loss of IκBα-mediated control over c-Rel leads to oncogenic activation of c-Rel.

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