The nuclear envelope and the organization of the pore complexes

Scheer, Ulrich; Dabauvalle, Marie-Christine; Merkert, Hilde; Benevente, Ricardo

doi:10.1016/0309-1651(88)90083-5

Cited by 54 publications

(45 citation statements)

References 38 publications

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“…The nudear envelope consists 01' the double-layered nudear membrane, the lamina d08cly apposed to the nue-O/fiJ/'il1l requcsts to: M,-C Daoauvalle lcoplasmie face 01' the inner nudear membrane ami numerous pore eomplexes traversing the perinuclear cisterna (for reeent reviews see Gerace and Burke 1988;Kessel 1988;Scheer et al 1988). During mitosis 01' higher eukaryotie eells the nuclear envclope and henee the eompartmentalization barrier between nucleus and cytoplasm transiently breaks down (" open mitosis ").…”

Section: Introductionmentioning

confidence: 99%

“…The in vitro assembled nuclear envelopes are structural and functional reproductions of the natural nuclear envelope: they are composed of an inner and outer membrane, a lamina layer underlying the inner nuclear membrane and numerous pore complexes (Newmeyer et al 1986a;Newport 1987;Lohka 1988;Newmeyer and Forbes 1988;Sheehan et al 1988; for morphological aspects of the native nuclear envelope of Xenopus 00-cytes see Scheer et al 1988). In addition, the in vitro reconstituted nuclei mimic the behaviour of normal nuclei in that they also transport karyophilic proteins through the pore complexes in a signal sequence and energy dependent manner (Newmeyer et al 1986 b;Newmeyer and Forbes 1988).…”

Section: Introductionmentioning

confidence: 99%

“…Recently a group ofpore complex glycoproteins with cytoplasmically or nucleoplasmically exposed O-linked N-acetylglucosamine (GlcNAc) residues has been identified (Davis and Blobel 1987;Hanover et al 1987;Holt et al 1987;Park et al 1987;Snow et al 1987;Scheer et al 1988; for review see Hart et al 1989). Members of this glycoprotein family are located within the pore channel proper and appear to be part of the pore transport machinery since nuclear protein uptake is inhibited by wheat germ agglutinin (WGA), a lectin which binds to their GlcNAc sugar moieties.…”

Section: Introductionmentioning

confidence: 99%

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Identification of a soluble precursor complex essential for nuclear pore assembly in vitro

1990

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Abstract. We analysed the soluble form in which the nudear pore complex protein p68 is stored in Xenopus /acpis eggs and its involvement in pore complex assembly processes, We have shown previously that p68, which is the major wheat germ agglutinin (WGA)-binding glycoprotein 01' nudear pore complexes from Xcnopus 00-cytes, is located in the pore channel and partieipates in mediated transport 01' karyophilic proteins. Using a monodonal antibody direeted against p68 (PlI) we re11l0ved this protein from XCIlOPUS egg extract by immunoadsorption, On addition 01' lambda DNA the immunodepleted extraet supported reconstitution ofnudei which were surrounded by a continuous double-membrane envdope but lacked pore complexes and were unable to import karyophilic pro teins such as nudeoplasmin or lamin L m , Essentially identical results were obtained with extract depleted 01' WGA-binding proteins. Our finding that both the anti-p68 antibody and WGA efficiently removed components from the extraet neeessary lor pore complex assembly but did not interfere with nudear membrane formation demonstrates that these processes are independent 01' each other. Analysis 01' the immunoprecipitate on silver-stained SDS-polyaerylamide gels indicated that the antibody adsorbed other proteins besides p68, notably two high molecular weight components. By sucrose gradient centrifugation and gel Illtration we showed that p68 together with associated protein(s) forms a stable, approximately globular eomplex with an M, 01' 254,000, a Stokes radius 01' 5.2 nm and a sedimentation coelTicient 01' 11.3 S. Our tinding that p68 occurs in the form 01' larger maeromolecular assemblies offers an explanation for the distinetly punctale immunofluorescence pattern observed in the eytoplasm 01' mitotic cells after staining with antibodies to p68.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Identification of a soluble precursor complex essential for nuclear pore assembly in vitro

1990

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“…Since WGA binds to a whole set of pore complex proteins with cytoplasmically or nucleoplasmically exposed O-linked GlcNAc moieties (Davis and Blobel 1987;Finlay et al 1987;Hanover et al 1987;Snow et al 1987 ;Scheer et al 1988; for review see , these studies could not identify the particular glycoprotein(s) involved in the translocation step. Recently, however, a monoclonal antibody reacting with a single pore complex-associated glycoprotein of Mr 68000 has been shown to inhibit nuclear protein uptake after microinjection into Xenopus oocytes (Dabauvalle et al 1988 a). This result suggested a crucial role of this major glycoprotein, which is located in the pore channel proper, for nuclear protein transport (Dabauvalle et al 1988 a ; see also Featherstone et al 1988).…”

Section: Introductionmentioning

confidence: 99%

Functional role of newly formed pore complexes in postmitotic nuclear reorganization

et al. 1989

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Abstract. Many nuclear proteins are released into the cytoplasm at prometaphase and are transported back into the daughter nuclei at the end of mitosis. To determine the role of this reentry in nuclear remodelling during early interphase, we experimentally manipulated nuclear protein uptake in dividing cells. Recently we and others have shown that signal-dependent, pore complex-mediated uptake of nuclear protein is blocked in living cells on microinjection of the lectin wheat germ agglutinin (WGA), or of antibodies such as PI1 that are directed against WGA-binding pore complex glycoproteins. In the present study, we microinjected mitotic PtK z cells with WGA or antibody PIt and followed nuclear reorganization of the daughter cells by immunofluorescence and electron microscopy. The inhibitory effect on nuclear protein uptake was monitored by co-injection of the karyophilic protein nucleoplasmin. When injected by itself early in mitosis, nucleoplasmin became sequestered into the daughter nuclei as they entered telophase. In contrast, nucleoplasmin was excluded from the daughter nuclei in the presence of WGA or antibody PI1 . Although PtK z cells with blocked nuclear protein uptake completed cytokinesis, their nuclei showed a telophaselike organization characterized by highly condensed chromatin surrounded by a nuclear envelope containing a few pore complexes. These findings suggest that pore complexes become functional as early as telophase, in close coincidence with nuclear envelope reformation. They further indicate that the extensive structural rearrangement of the nucleus during the telophase-G1 transition is dependent on the influx of karyophilic proteins from the cytoplasm through the pore complexes, and is not due solely to chromosome-associated components.

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“…While we used protein-free bacteriophage lambda DNA which, upon incubation in the egg extract is first assembled into nucleosomes and then into chromatin before it can serve as a template for nuclear envelope assembly [23], Finlay and Forbes [14] added demembranated sperm nuclei. Since it is well known that solubilization of nuclear membranes leaves behind a lamina-pore complex supramolecular structure (for examples see [26]), it is unclear whether the pore complexes described in this work are in fact newly assembled structures.Our results demonstrate that assembly of a continuous double-membrane nuclear envelope does not require concomitant pore complex formation. Hence they do not support the recently proposed "prepore model" which postulates that nascent pore complexes first have to bind to the chromatin surface in order to provide anchoring sites for nuclear membrane vesicles [28].…”

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confidence: 98%

Assembly of nuclear pore complexes in Xenopus egg extract

Dabauvalle

Scheer

1991

Biology of the Cell

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The nuclear pore complex: structural, functional and dynamic aspectsIn eukaryotic cells, chromatin is enclosed by a doublelayered membrane system, the nuclear envelope, which segregates the nuclear genome and its transcriptional apparatus from the cytoplasm. Major structural elements of the nuclear envelope include inner and outer nuclear membrane, a lamina composed of a network of intermediate filament-related proteins underlying the inner nuclear membrane and numerous pore complexes traversing the perinuclear cisterna (for recent reviews see [15,26)). Pore complexes provide plasmatic channels through the nuclear membrane barrier for nucleocytoplasmic exchange of proteins and RNA/RNP [13]. It is now well established that proteins destined for the nucleus (karyophilic proteins) must possess a specific localization signal sequence for their selective transport through the pore complexes (for recent review see [29)). By high resolution mapping of such karyophilic proteins en route through the pore center, localization of antibodies against specific pore complex constituents using immunogold electron microscopy, application of image processing techniques and quantitative electron microscopy, considerable progress has been made in the understanding of the functional organization of pore complexes at the molecular level (eg [1, 25)).A family of pore complex glycoproteins with cytoplasmically or nucleoplasmic ally exposed O-linked Nacetylglucosamine (GlcNAc) residues, whose members are located within the pore channel proper, appear to be part of the pore transport machinery. Thus, wheat germ agglutinin (WGA; a lectin which binds to terminal GlcNAcmoieties) as well as monoclonal antibodies against GlcNAc-modified pore proteins ("nucleoporins") have been shown to inhibit nuclear uptake of karyophilic proteins both in vivo and in vitro (for review see [29)).Due to the selective import of karyophilic proteins and exclusion of karyophobic proteins, the nuclear compartment has a protein composition that is markedly different from that of the cytoplasm (for details see [8,9)). However, during the "open" mitosis of higher eukaryotic cells this nucleocytoplasmic compartmentalization breaks down concomitantly with the disassembly of the nuclear envelope. The specific molecular environment within the postmitotic daughter nuclei is then progressively restored after reformation of the nuclear envelope by selective uptake of those nuclear proteins that became distributed throughout the cytoplasm during mitosis. The newly formed pore complexes play an essential part in this remigration of nuclear proteins. When pore-mediated transport is inhibited by microinjection of WGA or a porespecific monoclonal antibody (directed aginst p68; see below), daughter nuclei become enclosed by a nuclear envelope with pore complexes but yet remain arrested in a telophase-like situation, ie are unable to enlarge, to decondense their chromosomes and to reform nucleoli [5,6].The rapid and efficient assembly of functional pore complexes is thus of fundam...

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The nuclear envelope and the organization of the pore complexes

Cited by 54 publications

References 38 publications

Identification of a soluble precursor complex essential for nuclear pore assembly in vitro

Identification of a soluble precursor complex essential for nuclear pore assembly in vitro

Functional role of newly formed pore complexes in postmitotic nuclear reorganization

Assembly of nuclear pore complexes in Xenopus egg extract

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