scholarly journals The checkpoint-dependent nuclear accumulation of Rho1p exchange factor Rgf1p is important for tolerance to chronic replication stress

2014 ◽  
Vol 25 (7) ◽  
pp. 1137-1150 ◽  
Author(s):  
Sofía Muñoz ◽  
Elvira Manjón ◽  
Patricia García ◽  
Per Sunnerhagen ◽  
Yolanda Sánchez
Keyword(s):  
Rho Gtpases ◽  
Nuclear Export ◽  
Replication Stress ◽  
Nuclear Accumulation ◽  
Nuclear Localization Sequence ◽  
General Interest ◽  
Nucleotide Exchange ◽  
Replication Checkpoint ◽  
Exchange Factor ◽  
Localization Sequence

Guanine nucleotide exchange factors control many aspects of cell morphogenesis by turning on Rho-GTPases. The fission yeast exchange factor Rgf1p (Rho gef1) specifically regulates Rho1p during polarized growth and localizes to cortical sites. Here we report that Rgf1p is relocalized to the cell nucleus during the stalled replication caused by hydroxyurea (HU). Import to the nucleus is mediated by a nuclear localization sequence at the N-terminus of Rgf1p, whereas release into the cytoplasm requires two leucine-rich nuclear export sequences at the C-terminus. Moreover, Rgf1p nuclear accumulation during replication arrest depends on the 14-3-3 chaperone Rad24p and the DNA replication checkpoint kinase Cds1p. Both proteins control the nuclear accumulation of Rgf1p by inhibition of its nuclear export. A mutant, Rgf1p-9A, that substitutes nine serine potential phosphorylation Cds1p sites for alanine fails to accumulate in the nucleus in response to replication stress, and this correlates with a severe defect in survival in the presence of HU. In conclusion, we propose that the regulation of Rgf1p could be part of the mechanism by which Cds1p and Rad24p promote survival in the presence of chronic replication stress. It will be of general interest to understand whether the same is true for homologues of Rgf1p in budding yeast and higher eukaryotes.

scholarly journals Complex Formation with Monomeric α-Tubulin and Importin 13 Fosters c-Jun Protein Stability and Is Required for c-Jun’s Nuclear Translocation and Activity

Cancers ◽  
2019 ◽  
Vol 11 (11) ◽  
pp. 1806
Author(s):  
Melanie Kappelmann-Fenzl ◽  
Silke Kuphal ◽  
Rosemarie Krupar ◽  
Dirk Schadendorf ◽  
Viktor Umansky ◽  
...  
Keyword(s):  
Complex Formation ◽  
Protein Stability ◽  
Nuclear Translocation ◽  
Nuclear Accumulation ◽  
Nuclear Localization Sequence ◽  
Microtubule Network ◽  
Localization Sequence ◽  
Dynamic Structures ◽  
Main Regulator ◽  
Factor C

Microtubules are highly dynamic structures, which consist of α- and β-tubulin heterodimers. They are essential for a number of cellular processes, including intracellular trafficking and mitosis. Tubulin-binding chemotherapeutics are used to treat different types of tumors, including malignant melanoma. The transcription factor c-Jun is a central driver of melanoma development and progression. Here, we identify the microtubule network as a main regulator of c-Jun activity. Monomeric α-tubulin fosters c-Jun protein stability by protein–protein interaction. In addition, this complex formation is necessary for c-Jun’s nuclear localization sequence binding to importin 13, and consequent nuclear import and activity of c-Jun. A reduction in monomeric α-tubulin levels by treatment with the chemotherapeutic paclitaxel resulted in a decline in the nuclear accumulation of c-Jun in melanoma cells in an experimental murine model and in patients’ tissues. These findings add important knowledge to the mechanism of the action of microtubule-targeting drugs and indicate the newly discovered regulation of c-Jun by the microtubule cytoskeleton as a novel therapeutic target for melanoma and potentially also other types of cancer.

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.

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 Gef1p, a New Guanine Nucleotide Exchange Factor for Cdc42p, Regulates Polarity inSchizosaccharomyces pombe

2003 ◽  
Vol 14 (1) ◽  
pp. 313-323 ◽  
Author(s):  
Pedro M. Coll ◽  
Yadira Trillo ◽  
Amagoia Ametzazurra ◽  
Pilar Perez
Keyword(s):  
Cell Morphology ◽  
Rho Gtpases ◽  
Genetic Interaction ◽  
Guanine Nucleotide Exchange Factor ◽  
Guanine Nucleotide ◽  
Nucleotide Exchange ◽  
Exchange Factor ◽  
Guanine Nucleotide Exchange ◽  
Nucleotide Exchange Factor

Schizosaccharomyces pombe cdc42+regulates cell morphology and polarization of the actin cytoskeleton. Scd1p/Ral1p is the only described guanine nucleotide exchange factor (GEF) for Cdc42p in S. pombe. We have identified a new GEF, named Gef1p, specifically regulating Cdc42p. Gef1p binds to inactive Cdc42p but not to other Rho GTPases in two-hybrid assays. Overexpression of gef1+increases specifically the GTP-bound Cdc42p, and Gef1p is capable of stimulating guanine nucleotide exchange of Cdc42p in vitro. Overexpression ofgef1+causes changes in cell morphology similar to those caused by overexpression of the constitutively active cdc42G12V allele. Gef1p localizes to the septum. gef1+deletion is viable but causes a mild cell elongation and defects in bipolar growth and septum formation, suggesting a role for Gef1p in the control of cell polarity and cytokinesis. The double mutant gef1Δ scd1Δ is not viable, indicating that they share an essential function as Cdc42p activators. However, both deletion and overexpression of either gef1+orscd1+causes different morphological phenotypes, which suggest different functions. Genetic evidence revealed a link between Gef1p and the signaling pathway of Shk1/Orb2p and Orb6p. In contrast, no genetic interaction between Gef1p and Shk2p-Mkh1p pathway was observed.

Fragile X family members have important and non-overlapping functions

2011 ◽  
Vol 2 (5) ◽  
pp. 343-352 ◽  
Author(s):  
Claudia Winograd ◽  
Stephanie Ceman
Keyword(s):  
Nuclear Export ◽  
Rna Binding ◽  
Rna Binding Proteins ◽  
Fragile X ◽  
Family Members ◽  
Nuclear Localization Sequence ◽  
Interaction Domain ◽  
Protein Protein Interaction ◽  
Localization Sequence ◽  
Protein Functional Domains

AbstractThe fragile X family of genes encodes a small family of RNA binding proteins including FMRP, FXR1P and FXR2P that were identified in the 1990s. All three members are encoded by 17 exons and show alternative splicing at the 3′ ends of their respective transcripts. They share significant homology in the protein functional domains, including the Tudor domains, the nuclear localization sequence, a protein-protein interaction domain, the KH1 and KH2 domains and the nuclear export sequence. Fragile X family members are found throughout the animal kingdom, although all three members are not consistently present in species outside of mammals: only two family members are present in the avian species examined, Gallus gallus and Taeniopygia guttata, and in the frog Xenopus tropicalis. Although present in many tissues, the functions of the fragile X family members differ, which are particularly evident in knockout studies performed in animals. The fragile X family members play roles in normal neuronal function and in the case of FXR1, in muscle function.

scholarly journals Differential activation and function of Rho GTPases during Salmonella–host cell interactions

2006 ◽  
Vol 175 (3) ◽  
pp. 453-463 ◽  
Author(s):  
Jayesh C. Patel ◽  
Jorge E. Galán
Keyword(s):  
Rho Gtpases ◽  
Food Poisoning ◽  
Bacterial Pathogen ◽  
Cellular Responses ◽  
Host Cells ◽  
Nucleotide Exchange ◽  
Exchange Factor ◽  
Rho Family Gtpases ◽  
Rho Family ◽  
And Function

Salmonella enterica, the cause of food poisoning and typhoid fever, has evolved sophisticated mechanisms to modulate Rho family guanosine triphosphatases (GTPases) to mediate specific cellular responses such as actin remodeling, macropinocytosis, and nuclear responses. These responses are largely the result of the activity of a set of bacterial proteins (SopE, SopE2, and SopB) that, upon delivery into host cells via a type III secretion system, activate specific Rho family GTPases either directly (SopE and SopE2) or indirectly (SopB) through the stimulation of an endogenous exchange factor. We show that different Rho family GTPases play a distinct role in Salmonella-induced cellular responses. In addition, we report that SopB stimulates cellular responses by activating SH3-containing guanine nucleotide exchange factor (SGEF), an exchange factor for RhoG, which we found plays a central role in the actin cytoskeleton remodeling stimulated by Salmonella. These results reveal a remarkable level of complexity in the manipulation of Rho family GTPases by a bacterial pathogen.

scholarly journals Analysis of mutations in the putative nuclear localization sequence of interleukin-1β

1991 ◽  
Vol 280 (1) ◽  
pp. 111-116 ◽  
Author(s):  
S Grenfell ◽  
N Smithers ◽  
S Witham ◽  
A Shaw ◽  
P Graber ◽  
...  
Keyword(s):  
Nuclear Localization ◽  
Interleukin 1 ◽  
Simian Virus 40 ◽  
T Antigen ◽  
Nuclear Accumulation ◽  
Nuclear Localization Sequence ◽  
Target Cells ◽  
Wild Type ◽  
Receptor Mediated Endocytosis ◽  
Localization Sequence

Previous studies have shown that, after receptor-mediated endocytosis, interleukin-1 alpha (IL1 alpha) and interleukin-1 beta (IL1 beta) are translocated to the nucleus, where they appear to accumulate. It has been suggested that nuclear translocation may be involved in the biological responsiveness of target cells to IL1 stimulation. The human IL1 beta molecule contains a seven-amino-acid sequence (-Pro208-Lys-Lys-Lys-Met-Glu-Lys-) that shows some sequence identity with the nuclear localization sequence of the simian-virus-40 large T-antigen. The effects of point mutations within this putative nuclear localization sequence on IL1 beta binding, receptor-mediated endocytosis and biological activity have been characterized. Mutants M49 (Lys210→Ala), M50 (Lys211→Ala) and M51 (Pro208→Ala) all retained the ability to bind to the IL1 receptor, albeit with lower affinity than the wild-type molecules. However, mutants M49, M50 and M51 showed greater biological potency than wild-type IL1 alpha or IL1 beta, as measured by the induction of IL2 secretion. However, receptor-mediated endocytosis and nuclear accumulation of M50 were comparable with those in the wild-type. These observations suggest that the putative nuclear localization sequence may play an important role in the generation of biological responses to IL1 stimulation, even though it may not influence internalization of the ligand.

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