scholarly journals Essential Role of Nuclear Localization for Yeast Ulp2 SUMO Protease Function

2009 ◽  
Vol 20 (8) ◽  
pp. 2196-2206 ◽  
Author(s):  
Mary B. Kroetz ◽  
Dan Su ◽  
Mark Hochstrasser
Keyword(s):  
Nuclear Localization ◽  
Nuclear Protein ◽  
Catalytic Domain ◽  
Yeast Growth ◽  
Nuclear Targeting ◽  
Sumo Protease ◽  
Sumo Proteases ◽  
Localization Signal

The SUMO protein is covalently attached to many different substrates throughout the cell. This modification is rapidly reversed by SUMO proteases. The Saccharomyces cerevisiae SUMO protease Ulp2 is a nuclear protein required for chromosome stability and cell cycle restart after checkpoint arrest. Ulp2 is related to the human SENP6 protease, also a nuclear protein. All members of the Ulp2/SENP6 family of SUMO proteases have large but poorly conserved N-terminal domains (NTDs) adjacent to the catalytic domain. Ulp2 also has a long C-terminal domain (CTD). We show that CTD deletion has modest effects on yeast growth, but poly-SUMO conjugates accumulate. In contrast, the NTD is essential for Ulp2 function and is required for nuclear targeting. Two short, widely separated sequences within the NTD confer nuclear localization. Efficient Ulp2 import into the nucleus requires the β-importin Kap95, which functions on classical nuclear-localization signal (NLS)-bearing substrates. Remarkably, replacement of the entire >400-residue NTD by a heterologous NLS results in near-normal Ulp2 function. These data demonstrate that nuclear localization of Ulp2 is crucial in vivo, yet only small segments of the NTD provide the key functional elements, explaining the minimal sequence conservation of the NTDs in the Ulp2/SENP6 family of enzymes.

The role of nucleoplasmin in chromatin assembly and disassembly

1993 ◽  
Vol 339 (1289) ◽  
pp. 263-269 ◽  
Keyword(s):  
Nuclear Protein ◽  
Sperm Chromatin ◽  
Signal Presentation ◽  
Localization Signal ◽  
Heat Shock Cognate Protein ◽  
Chromatin Assembly And Disassembly ◽  
Cognate Protein

Nucleoplasmin is the most abundant nuclear protein in Xenopus oocytes and eggs. The term ‘molecular chaperone’ was coined to describe its role in the assembly of the nucleosome subunits of chromatin. Although histones and DNA can self-assemble into nucleosomes, nucleoplasmin can facilitate this process in vitro by competing against non-specific charge interactions. In vivo nucleoplasmin binds histones H2A and H2B and transfers them to DNA. Another acidic nuclear protein, N l, binds and transfers histones H3 and H4. Nucleoplasmin has at least one other role in modulating chromatin structure in Xenopus eggs. It is required for the first stage of sperm chromatin decondensation. It binds and removes sperm basic proteins and replaces them by histones H2A and H2B, again forming nucleosomes, and resulting in decondensation of the compacted sperm chromatin. In addition we propose that the properties of the nuclear localization signal of nucleoplasmin can be explained by a model in which heat shock cognate protein hsc70 has a chaperone role in signal presentation during nuclear transport.

scholarly journals Alternative splicing introduces a nuclear localization signal that targets multifunctional CaM kinase to the nucleus.

1994 ◽  
Vol 126 (4) ◽  
pp. 839-852 ◽  
Author(s):  
M Srinivasan ◽  
C F Edman ◽  
H Schulman
Keyword(s):  
Alternative Splicing ◽  
Nuclear Localization ◽  
Nuclear Localization Signal ◽  
Variable Domain ◽  
Site Directed Mutagenesis ◽  
Cam Kinase ◽  
Nuclear Targeting ◽  
Intracellular Targeting ◽  
Localization Signal

Intracellular targeting may enable protein kinases with broad substrate-specificities, such as multifunctional Ca2+/calmodulin-dependent protein kinase (CaM kinase) to achieve a selectivity of action in vivo. We have examined the intracellular targeting of three delta-CaM kinase isoforms. The delta B-CaM kinase isoform is targeted to the nucleus in transfected cells while the delta A- and delta C-CaM kinase isoforms are cytosolic/cytoskeletal. A chimeric construct of alpha-CaM kinase containing the delta B-CaM kinase variable domain is rerouted to the nucleus while the native alpha-CaM kinase and chimeras of alpha-CaM kinase which contain the delta A- or delta C-CaM kinase variable domains are retained in the cytoplasm. Using site-directed mutagenesis, we have defined a nuclear localization signal (NLS) within an 11-amino acid sequence, likely inserted by alternative splicing, in the variable domain of delta B-CaM kinase. Isoform-specific nuclear targeting of CaM kinase is probably a key mechanism in the selective regulation of nuclear functions by CaM kinase. CaM kinase is a multimer that can be composed of several isoforms. We find that when cells express two different isoforms of CaM kinase, cellular targeting is determined by the ratio of the isoforms. When an excess of the cytoplasmic isoform of CaM kinase is coexpressed along with the nuclear isoform, both isoforms are localized in the cytoplasm. Conversely an excess of the nuclear isoform can reroute the cytoplasmic isoform to the nucleus. The nuclear isoform likely coassembles with the cytosolic isoform, to form a heteromultimeric holoenzyme which is transported into the nucleus. These experiments demonstrate isoform-specific targeting of CaM kinase and indicate that such targeting can be modified by the expression of multiple isoforms of the enzyme.

scholarly journals Coordinate Nuclear Targeting of the FANCD2 and FANCI Proteins via a FANCD2 Nuclear Localization Signal

PLoS ONE ◽  
2013 ◽  
Vol 8 (11) ◽  
pp. e81387 ◽  
Author(s):  
Rebecca A. Boisvert ◽  
Meghan A. Rego ◽  
Paul A. Azzinaro ◽  
Maurizio Mauro ◽  
Niall G. Howlett
Keyword(s):  
Nuclear Localization ◽  
Nuclear Localization Signal ◽  
Nuclear Targeting ◽  
Localization Signal

scholarly journals Recruitment and the Role of Nuclear Localization in Polyglutamine-mediated Aggregation

1998 ◽  
Vol 143 (6) ◽  
pp. 1457-1470 ◽  
Author(s):  
Matthew K. Perez ◽  
Henry L. Paulson ◽  
Sagun J. Pendse ◽  
Sarah J. Saionz ◽  
Nancy M. Bonini ◽  
...  
Keyword(s):  
Nuclear Localization ◽  
Green Fluorescence Protein ◽  
Spinocerebellar Ataxia Type ◽  
Spinocerebellar Ataxia Type 3 ◽  
Eyes Absent ◽  
Disease Protein ◽  
Glutamine Repeat ◽  
Type 3

The inherited neurodegenerative diseases caused by an expanded glutamine repeat share the pathologic feature of intranuclear aggregates or inclusions (NI). Here in cell-based studies of the spinocerebellar ataxia type-3 disease protein, ataxin-3, we address two issues central to aggregation: the role of polyglutamine in recruiting proteins into NI and the role of nuclear localization in promoting aggregation. We demonstrate that full-length ataxin-3 is readily recruited from the cytoplasm into NI seeded either by a pathologic ataxin-3 fragment or by a second unrelated glutamine-repeat disease protein, ataxin-1. Experiments with green fluorescence protein/polyglutamine fusion proteins show that a glutamine repeat is sufficient to recruit an otherwise irrelevant protein into NI, and studies of human disease tissue and a Drosophila transgenic model provide evidence that specific glutamine-repeat–containing proteins, including TATA-binding protein and Eyes Absent protein, are recruited into NI in vivo. Finally, we show that nuclear localization promotes aggregation: an ataxin-3 fragment containing a nonpathologic repeat of 27 glutamines forms inclusions only when targeted to the nucleus. Our findings establish the importance of the polyglutamine domain in mediating recruitment and suggest that pathogenesis may be linked in part to the sequestering of glutamine-containing cellular proteins. In addition, we demonstrate that the nuclear environment may be critical for seeding polyglutamine aggregates.

scholarly journals BCL3 encodes a nuclear protein which can alter the subcellular location of NF-kappa B proteins.

1994 ◽  
Vol 14 (6) ◽  
pp. 3915-3926 ◽  
Author(s):  
Q Zhang ◽  
J A Didonato ◽  
M Karin ◽  
T W McKeithan
Keyword(s):  
Nuclear Localization Signal ◽  
Nuclear Protein ◽  
Subcellular Location ◽  
Lymphocytic Leukemia ◽  
Wild Type ◽  
Nf Kappa B ◽  
Subnuclear Localization ◽  
I Kappa B Alpha ◽  
Localization Signal

BCL3 is a candidate proto-oncogene involved in the recurring translocation t(14;19) found in some patients with chronic lymphocytic leukemia. BCL3 protein acts as an I kappa B in that it can specifically inhibit the DNA binding of NF-kappa B factors. Here, we demonstrate that BCL3 is predominantly a nuclear protein and provide evidence that its N terminus is necessary to direct the protein into the nucleus. In contrast to I kappa B alpha (MAD3), BCL3 does not cause NF-kappa B p50 to be retained in the cytoplasm; instead, in cotransfection assays, it alters the subnuclear localization of p50. The two proteins colocalize, suggesting that they interact in vivo. Further immunofluorescence experiments showed that a mutant p50, lacking a nuclear localization signal and restricted to the cytoplasm, is brought into the nucleus in the presence of BCL3. Correspondingly, a wild-type p50 directs into the nucleus a truncated BCL3, which, when transfected alone, is found in the cytoplasm. We tested whether BCL3 could overcome the cytoplasmic retention of p50 by I kappa B alpha. Results from triple cotransfection experiments with BCL3, I kappa B alpha, and p50 implied that BCL3 can successfully compete with I kappa B alpha and bring p50 into the nucleus; thus, localization of NF-kappa B factors may be affected by differential expression of I kappa B proteins. These novel properties of BCL3 protein further establish BCL3 as a distinctive member of the I kappa B family.

scholarly journals Regulated nuclear import of the Drosophila rel protein dorsal: structure-function analysis.

1996 ◽  
Vol 16 (3) ◽  
pp. 1103-1114 ◽  
Author(s):  
S Govind ◽  
E Drier ◽  
L H Huang ◽  
R Steward
Keyword(s):  
Amino Acids ◽  
Structure Function ◽  
Nuclear Localization ◽  
Nuclear Import ◽  
Function Analysis ◽  
Drosophila Embryo ◽  
Nuclear Targeting ◽  
Homology Region ◽  
Early Drosophila Embryo

The formation of a gradient of nuclear Dorsal protein in the early Drosophila embryo is the last step in a maternally encoded dorsal-ventral signal transduction pathway. This gradient is formed in response to a ventral signal, which leads to the dissociation of cytoplasmic Dorsal from the I kappa B homolog Cactus. Free Dorsal is then targeted to the nucleus. Dorsal is a Rel-family transcription factor. Signal-dependent nuclear localization characterizes the regulation of Rel proteins. In order to identify regions of Dorsal that are essential for its homodimerization, nuclear targeting, and interaction with Cactus, we have performed an in vivo structure-function analysis. Our results show that all these functions are carried out by regions within the conserved Rel-homology region of Dorsal. The C-terminal divergent half of Dorsal is dispensable for its selective nuclear import. A basic stretch of 6 amino acids at the C terminus of the Rel-homology region is necessary for nuclear localization. This nuclear localization signal is not required for Cactus binding. Removal of the N-terminal 40 amino acids abolished the nuclear import of Dorsal, uncovering a potentially novel function for this highly conserved region.

scholarly journals Cse1p Is Involved in Export of Yeast Importin α from the Nucleus

1998 ◽  
Vol 18 (11) ◽  
pp. 6805-6815 ◽  
Author(s):  
Jens Solsbacher ◽  
Patrick Maurer ◽  
F. Ralf Bischoff ◽  
Gabriel Schlenstedt
Keyword(s):  
Nuclear Export ◽  
Fluorescent Protein ◽  
Nuclear Pore ◽  
Wild Type ◽  
Importin Α ◽  
Localization Signal ◽  
Green Fluorescent ◽  
Mutant Cells

ABSTRACT Proteins bearing a nuclear localization signal (NLS) are targeted to the nucleus by the heterodimeric transporter importin. Importin α binds to the NLS and to importin β, which carries it through the nuclear pore complex (NPC). Importin disassembles in the nucleus, evidently by binding of RanGTP to importin β. The importin subunits are exported separately. We investigated the role of Cse1p, theSaccharomyces cerevisiae homologue of human CAS, in nuclear export of Srp1p (yeast importin α). Cse1p is located predominantly in the nucleus but also is present in the cytoplasm and at the NPC. We analyzed the in vivo localization of the importin subunits fused to the green fluorescent protein in wild-type and cse1-1 mutant cells. Srp1p but not importin β accumulated in nuclei ofcse1-1 mutants, which are defective in NLS import but not defective in NLS-independent import pathways. Purified Cse1p binds with high affinity to Srp1p only in the presence of RanGTP. The complex is dissociated by the cytoplasmic RanGTP-binding protein Yrb1p. Combined with the in vivo results, this suggests that a complex containing Srp1p, Cse1p, and RanGTP is exported from the nucleus and is subsequently disassembled in the cytoplasm by Yrb1p. The formation of the trimeric Srp1p-Cse1p-RanGTP complex is inhibited by NLS peptides, indicating that only NLS-free Srp1p will be exported to the cytoplasm.

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