scholarly journals BIM1Encodes a Microtubule-binding Protein in Yeast

1997 ◽  
Vol 8 (12) ◽  
pp. 2677-2691 ◽  
Author(s):  
Katja Schwartz ◽  
Kristy Richards ◽  
David Botstein
Keyword(s):  
Fluorescent Protein ◽  
Synthetic Lethality ◽  
Binding Protein ◽  
Human Colon ◽  
Wild Type ◽  
Human Colon Cancer ◽  
Microtubule Binding ◽  
Green Fluorescent ◽  
Two Hybrid

A previously uncharacterized yeast gene (YER016w) that we have named BIM1 (binding to microtubules) was obtained from a two-hybrid screen of a yeast cDNA library using as bait the entire coding sequence of TUB1 (encoding α-tubulin). Deletion of BIM1 results in a strong bilateral karyogamy defect, hypersensitivity to benomyl, and aberrant spindle behavior, all phenotypes associated with mutations affecting microtubules in yeast, and inviability at extreme temperatures (i.e., ≥37°C or ≤14°C). Overexpression of BIM1 in wild-type cells is lethal. A fusion of Bim1p with green fluorescent protein that complements the bim1Δ phenotypes allows visualization in vivo of both intranuclear spindles and extranuclear microtubules in otherwise wild-type cells. A bim1deletion displays synthetic lethality with deletion alleles ofbik1, num1, and bub3 as well as a limited subset of tub1 conditional-lethal alleles. A systematic study of 51 tub1 alleles suggests a correlation between specific failure to interact with Bim1p in the two-hybrid assay and synthetic lethality with thebim1Δ allele. The sequence of BIM1shows substantial similarity to sequences from organisms across the evolutionary spectrum. One of the human homologues, EB1, has been reported previously as binding APC, itself a microtubule-binding protein and the product of a gene implicated in the etiology of human colon cancer.

scholarly journals Mechanism of Aurora-B Degradation and Its Dependency on Intact KEN and A-Boxes: Identification of an Aneuploidy-Promoting Property

2005 ◽  
Vol 25 (12) ◽  
pp. 4977-4992 ◽  
Author(s):  
Hao G. Nguyen ◽  
Dharmaraj Chinnappan ◽  
Takeshi Urano ◽  
Katya Ravid
Keyword(s):  
Chromosome Segregation ◽  
Fluorescent Protein ◽  
Point Mutations ◽  
Degradation Pathway ◽  
Aurora B ◽  
Stable Form ◽  
Wild Type ◽  
Green Fluorescent ◽  
Critical Regions

ABSTRACT The kinase Aurora-B, a regulator of chromosome segregation and cytokinesis, is highly expressed in a variety of tumors. During the cell cycle, the level of this protein is tightly controlled, and its deregulated abundance is suspected to contribute to aneuploidy. Here, we provide evidence that Aurora-B is a short-lived protein degraded by the proteasome via the anaphase-promoting cyclosome complex (APC/c) pathway. Aurora-B interacts with the APC/c through the Cdc27 subunit, Aurora-B is ubiquitinated, and its level is increased upon treatment with inhibitors of the proteasome. Aurora-B binds in vivo to the degradation-targeting proteins Cdh1 and Cdc20, the overexpression of which accelerates Aurora-B degradation. Using deletions or point mutations of the five putative degradation signals in Aurora-B, we show that degradation of this protein does not depend on its D-boxes (RXXL), but it does require intact KEN boxes and A-boxes (QRVL) located within the first 65 amino acids. Cells transfected with wild-type or A-box-mutated or KEN box-mutated Aurora-B fused to green fluorescent protein display the protein localized to the chromosomes and then to the midzone during mitosis, but the mutated forms are detected at greater intensities. Hence, we identified the degradation pathway for Aurora-B as well as critical regions for its clearance. Intriguingly, overexpression of a stable form of Aurora-B alone induces aneuploidy and anchorage-independent growth.

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.

scholarly journals Bim1p/Yeb1p Mediates the Kar9p-dependent Cortical Attachment of Cytoplasmic Microtubules

2000 ◽  
Vol 11 (9) ◽  
pp. 2949-2959 ◽  
Author(s):  
Rita K. Miller ◽  
Soo-Chen Cheng ◽  
Mark D. Rose
Keyword(s):  
Fluorescent Protein ◽  
Binding Protein ◽  
Spindle Pole Body ◽  
Attachment Site ◽  
Spindle Pole ◽  
Cell Cortex ◽  
Microtubule Binding ◽  
Pole Body ◽  
Cytoplasmic Microtubules ◽  
Two Hybrid

In Saccharomyces cerevisiae, positioning of the mitotic spindle depends on the interaction of cytoplasmic microtubules with the cell cortex. In this process, cortical Kar9p in the bud acts as a link between the actin and microtubule cytoskeletons. To identify Kar9p-interacting proteins, a two-hybrid screen was conducted with the use of full-length Kar9p as bait, and three genes were identified: BIM1, STU2, andKAR9 itself. STU2 encodes a component of the spindle pole body. Bim1p is the yeast homologue of the human microtubule-binding protein EB1, which is a binding partner to the adenomatous polyposis coli protein involved in colon cancer. Eighty-nine amino acids within the third quarter of Bim1p was sufficient to confer interaction with Kar9p. The two-hybrid interactions were confirmed with the use of coimmunoprecipitation experiments. Genetic analysis placed Bim1p in the Kar9p pathway for nuclear migration. Bim1p was not required for Kar9p's cortical or spindle pole body localization. However, deletion ofBIM1 eliminated Kar9p localization along cytoplasmic microtubules. Furthermore, in the bim1 mutants, the cytoplasmic microtubules no longer intersected the cortical dot of Green Fluorescent Protein–Kar9p. These experiments demonstrate that the interaction of cytoplasmic microtubules with the Kar9p cortical attachment site requires the microtubule-binding protein Bim1p.

scholarly journals SLAM (CD150)-Independent Measles Virus Entry as Revealed by Recombinant Virus Expressing Green Fluorescent Protein

2002 ◽  
Vol 76 (13) ◽  
pp. 6743-6749 ◽  
Author(s):  
Koji Hashimoto ◽  
Nobuyuki Ono ◽  
Hironobu Tatsuo ◽  
Hiroko Minagawa ◽  
Makoto Takeda ◽  
...  
Keyword(s):  
Green Fluorescent Protein ◽  
Measles Virus ◽  
Fluorescent Protein ◽  
Infected Individual ◽  
Lymphocyte Activation ◽  
Wild Type ◽  
Low Efficiency ◽  
Histopathological Studies ◽  
Green Fluorescent

ABSTRACT Wild-type measles virus (MV) strains use human signaling lymphocyte activation molecule (SLAM) as a cellular receptor, while vaccine strains such as the Edmonston strain can use both SLAM and CD46 as receptors. Although the expression of SLAM is restricted to cells of the immune system (lymphocytes, dendritic cells, and monocytes), histopathological studies with humans and experimentally infected monkeys have shown that MV also infects SLAM-negative cells, including epithelial, endothelial, and neuronal cells. In an attempt to explain these findings, we produced the enhanced green fluorescent protein (EGFP)-expressing recombinant MV (IC323-EGFP) based on the wild-type IC-B strain. IC323-EGFP showed almost the same growth kinetics as the parental recombinant MV and produced large syncytia exhibiting green autofluorescence in SLAM-positive cells. Interestingly, all SLAM-negative cell lines examined also showed green autofluorescence after infection with IC323-EGFP, although the virus hardly spread from the originally infected individual cells and thus did not induce syncytia. When the number of EGFP-expressing cells after infection was taken as an indicator, the infectivities of IC323-EGFP for SLAM-negative cells were 2 to 3 logs lower than those for SLAM-positive cells. Anti-MV hemagglutinin antibody or fusion block peptide, but not anti-CD46 antibody, blocked IC323-EGFP infection of SLAM-negative cells. This infection occurred under conditions in which entry via endocytosis was inhibited. These results indicate that MV can infect a variety of cells, albeit with a low efficiency, by using an as yet unidentified receptor(s) other than SLAM or CD46, in part explaining the observed MV infection of SLAM-negative cells in vivo.

scholarly journals Yeast Nucleoporins Involved in Passive Nuclear Envelope Permeability

2000 ◽  
Vol 149 (5) ◽  
pp. 1027-1038 ◽  
Author(s):  
Nataliya Shulga ◽  
Nima Mosammaparast ◽  
Richard Wozniak ◽  
David S. Goldfarb
Keyword(s):  
Nuclear Envelope ◽  
Fluorescent Protein ◽  
Nuclear Pore ◽  
Wild Type ◽  
Transport Channel ◽  
Diffusion Channel ◽  
Gfp Reporter ◽  
Green Fluorescent ◽  
Gfp Reporters

The vertebrate nuclear pore complex (NPC) harbors an ∼10-nm diameter diffusion channel that is large enough to admit 50-kD polypeptides. We have analyzed the permeability properties of the Saccharomyces cerevisiae nuclear envelope (NE) using import (NLS) and export (NES) signal-containing green fluorescent protein (GFP) reporters. Compared with wild-type, passive export rates of a classical karyopherin/importin (Kap) Kap60p/Kap95p-targeted NLS-GFP reporter (cNLS-GFP) were significantly faster in nup188-Δ and nup170-Δ cells. Similar results were obtained using two other NLS-GFP reporters, containing either the Kap104p-targeted Nab2p NLS (rgNLS) or the Kap121p-targeted Pho4p NLS (pNLS). Elevated levels of Hsp70 stimulated cNLS-GFP import, but had no effect on the import of rgNLS-GFP. Thus, the role of Hsp70 in NLS-directed import may be NLS- or targeting pathway-specific. Equilibrium sieving limits for the diffusion channel were assessed in vivo using NES-GFP reporters of 36–126 kD and were found to be greater than wild-type in nup188-Δ and nup170-Δ cells. We propose that Nup170p and Nup188p are involved in establishing the functional resting diameter of the NPC's central transport channel.

scholarly journals Functional Display of an α2 Integrin-Specific Motif (RKK) on the Surface of Baculovirus Particles

2005 ◽  
Vol 4 (4) ◽  
pp. 437-445 ◽  
Author(s):  
Reetta Riikonen ◽  
Heli Matilainen ◽  
Nina Rajala ◽  
Olli Pentikäinen ◽  
Mark Johnson ◽  
...  
Keyword(s):  
Envelope Protein ◽  
Mammalian Cells ◽  
Fluorescent Protein ◽  
Recombinant Baculovirus ◽  
Autographa Californica ◽  
Wild Type ◽  
Receptor Binding Site ◽  
Mammalian Cell Lines ◽  
Green Fluorescent

The use of baculovirus vectors shows promise as a tool for gene delivery into mammalian cells. These insect viruses have been shown to transduce a variety of mammalian cell lines, and gene transfer has also been demonstrated in vivo. In this study, we generated two recombinant baculovirus vectors displaying an integrin-specific motif, RKK, as a part of two different loops of the green fluorescent protein (GFP) fused with the major envelope protein gp64 of Autographa californica M nucleopolyhedrovirus. By enzyme linked immunosorbent assays, these viruses were shown to bind a peptide representing the receptor binding site of an α2 integrin, the α2I-domain. However, the interaction was not strong enough to overcome binding of wild type gp64 to the unknown cellular receptor(s) on the surface of α2 integrin-expressing cells (CHO-α2β1) or enhance the viral uptake. After treatment of these cells with phospholipase C, internalization of all viruses was blocked or decreased significantly. However, one of the RKK displaying viruses, AcGFP(K)gp64, was still able to internalize into CHO-α2β1 cells, although at a lower level as compared to non-treated cells. This may indicate the possible utilization of a PLC independent alternative route via, in this case, the α2β1 integrin.

scholarly journals A Novel In Vivo Assay Reveals Inhibition of Ribosomal Nuclear Export in Ran-Cycle and Nucleoporin Mutants

1999 ◽  
Vol 144 (3) ◽  
pp. 389-401 ◽  
Author(s):  
Ed Hurt ◽  
Stefan Hannus ◽  
Birgit Schmelzl ◽  
Denise Lau ◽  
David Tollervey ◽  
...  
Keyword(s):  
Nuclear Export ◽  
Fluorescent Protein ◽  
Dominant Negative ◽  
Nuclear Accumulation ◽  
Wild Type ◽  
Ribosomal Subunits ◽  
In Vivo Assay ◽  
Green Fluorescent ◽  
Transport Factors

To identify components involved in the nuclear export of ribosomes in yeast, we developed an in vivo assay exploiting a green fluorescent protein (GFP)-tagged version of ribosomal protein L25. After its import into the nucleolus, L25-GFP assembles with 60S ribosomal subunits that are subsequently exported into the cytoplasm. In wild-type cells, GFP-labeled ribosomes are only detected by fluorescence in the cytoplasm. However, thermosensitive rna1-1 (Ran-GAP), prp20-1 (Ran-GEF), and nucleoporin nup49 and nsp1 mutants are impaired in ribosomal export as revealed by nuclear accumulation of L25-GFP. Furthermore, overexpression of dominant-negative RanGTP (Gsp1-G21V) and the tRNA exportin Los1p inhibits ribosomal export. The pattern of subnuclear accumulation of L25-GFP observed in different mutants is not identical, suggesting that transport can be blocked at different steps. Thus, nuclear export of ribosomes requires the nuclear/cytoplasmic Ran-cycle and distinct nucleoporins. This assay can be used to identify soluble transport factors required for nuclear exit of ribosomes.

scholarly journals Patterning and growth control in vivo by an engineered GFP gradient

Science ◽  
2020 ◽  
Vol 370 (6514) ◽  
pp. 321-327 ◽  
Author(s):  
Kristina S. Stapornwongkul ◽  
Marc de Gennes ◽  
Luca Cocconi ◽  
Guillaume Salbreux ◽  
Jean-Paul Vincent
Keyword(s):  
Fluorescent Protein ◽  
Growth Control ◽  
Positional Information ◽  
Morphogen Gradient ◽  
Length Scale ◽  
Wild Type ◽  
Morphogen Gradients ◽  
Gradient Formation ◽  
Green Fluorescent

Morphogen gradients provide positional information during development. To uncover the minimal requirements for morphogen gradient formation, we have engineered a synthetic morphogen in Drosophila wing primordia. We show that an inert protein, green fluorescent protein (GFP), can form a detectable diffusion-based gradient in the presence of surface-associated anti-GFP nanobodies, which modulate the gradient by trapping the ligand and limiting leakage from the tissue. We next fused anti-GFP nanobodies to the receptors of Dpp, a natural morphogen, to render them responsive to extracellular GFP. In the presence of these engineered receptors, GFP could replace Dpp to organize patterning and growth in vivo. Concomitant expression of glycosylphosphatidylinositol (GPI)–anchored nonsignaling receptors further improved patterning, to near–wild-type quality. Theoretical arguments suggest that GPI anchorage could be important for these receptors to expand the gradient length scale while at the same time reducing leakage.

scholarly journals Analysis of MAP 4 function in living cells using green fluorescent protein (GFP) chimeras.

1995 ◽  
Vol 130 (3) ◽  
pp. 639-650 ◽  
Author(s):  
K R Olson ◽  
J R McIntosh ◽  
J B Olmsted
Keyword(s):  
Green Fluorescent Protein ◽  
Fluorescent Protein ◽  
Microtubule Organization ◽  
Microtubule Binding ◽  
Binding Characteristics ◽  
Basic Domain ◽  
In Vivo Analysis ◽  
Projection Domain ◽  
Green Fluorescent

MAP 4 is a ubiquitous microtubule-associated protein thought to play a role in the polymerization and stability of microtubules in interphase and mitotic cells. We have analyzed the behavior of protein domains of MAP 4 in vivo using chimeras constructed from these polypeptides and the green fluorescent protein (GFP). GFP-MAP 4 localizes to microtubules; this is confirmed by colocalization of GFP-MAP 4 with microtubules that have incorporated microinjected rhodamine-tubulin, and by loss of localized fluorescence after treatment of cells with anti-microtubule agents. Different subdomains of MAP 4 have distinct effects on microtubule organization and dynamics. The entire basic domain of MAP 4 reorganizes microtubules into bundles and stabilizes these arrays against depolymerization with nocodazole. Within the basic domain, the PGGG repeats, which are conserved with MAP 2 and tau, have a weak affinity for microtubules and are dispensable for microtubule binding, whereas the MAP 4-unique PSP region can function independently in binding. The projection domain shows no microtubule localization, but does modulate the association of various binding subdomains with microtubules. The acidic carboxy terminus of MAP 4 strongly affects the microtubule binding characteristics of the other domains, despite constituting less than 6% of the protein. These data show that MAP 4 association with microtubules is modulated by sequences both within and outside the basic domain. Further, our work demonstrates that GFP chimeras will allow an in vivo analysis of the effects of MAPs and their variants on microtubule dynamics in real time.

scholarly journals E-MAP-115 (ensconsin) associates dynamically with microtubules in vivo and is not a physiological modulator of microtubule dynamics

1999 ◽  
Vol 112 (23) ◽  
pp. 4243-4255 ◽  
Author(s):  
K. Faire ◽  
C.M. Waterman-Storer ◽  
D. Gruber ◽  
D. Masson ◽  
E.D. Salmon ◽  
...  
Keyword(s):  
Fluorescent Protein ◽  
Time Lapse ◽  
Microtubule Dynamics ◽  
Polymerization Reaction ◽  
Physiological Level ◽  
Microtubule Binding ◽  
Binding Function ◽  
Associated Proteins ◽  
Green Fluorescent

Microtubule-associated proteins (MAPs) have been hypothesized to regulate microtubule dynamics and/or functions. To test hypotheses concerning E-MAP-115 (ensconsin) function, we prepared stable cell lines expressing conjugates in which the full-length MAP (Ensc) or its microtubule-binding domain (EMTB) was conjugated to one or more green fluorescent protein (GFP) molecules. Because both distribution and microtubule-binding properties of GFP-Ensc, GFP-EMTB, and 2x, 3x, or 4xGFP-EMTB chimeras all appeared to be identical to those of endogenous E-MAP-115 (ensconsin), we used the 2xGFP-EMTB molecule as a reporter for the behavior and microtubule-binding function of endogenous MAP. Dual wavelength time-lapse fluorescence imaging of 2xGFP-EMTB in cells microinjected with labeled tubulin revealed that this GFP-MAP chimera associated with the lattice of all microtubules immediately upon polymerization and dissociated concomitant with depolymerization, suggesting that dynamics of MAP:microtubule interactions were at least as rapid as tubulin:microtubule dynamics in the polymerization reaction. Presence of both GFP-EMTB chimeras and endogenous E-MAP-115 (ensconsin) along apparently all cellular microtubules at all cell cycle stages suggested that the MAP might function in modulating stability or dynamics of microtubules, a capability shown previously in transiently transfected cells. Although cells with extremely high expression levels of GFP-EMTB chimera exhibited stabilized microtubules, cells expressing four to ten times the physiological level of endogenous MAP exhibited microtubule dynamics indistinguishable from those of untransfected cells. This result shows that E-MAP-115 (ensconsin) is unlikely to function as a microtubule stabilizer in vivo. Instead, this MAP most likely serves to modulate microtubule functions or interactions with other cytoskeletal elements.

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