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PubMed1983

Nuclear structure: determination of the fate of the nuclear envelope in Drosophila during mitosis using monoclonal antibodies.

Libraries of monoclonal antibody against nuclear proteins of Drosophila melanogaster have been established recently to investigate nuclear structure and function. Some of the antibodies have been characterized as being directed against the nuclear envelope. Further studies detailed in this paper describe the fate of the nuclear envelope during mitosis. Indirect immunofluorescence staining of whole developing Drosophila embryos has been used as a system in which nuclear events can be studied both synchronously and in a longitudinal gradient of mitotic structures. The results show a pattern of breakdown and reconstruction of the nuclear envelope in which the antigen is always present in particulate structures. In addition, the processes of antigen rearrangement are shown to be spatially determined throughout mitosis.

Animals↗
PubMed2003

Profile and clinical significance of anti-nuclear envelope antibodies found in patients with primary biliary cirrhosis: a multicenter study.

Primary biliary cirrhosis (PBC) sera contain antibodies which recognize various nuclear envelope proteins of which antibody against gp210 has been proven to be diagnostic for disease. In contrast, the clinical significance of another nuclear envelope antibody, anti-p62 antibody has not been well investigated. In the present study, we have analyzed anti-nuclear envelope antibodies by indirect immunofluorescence and immunoblot using rat liver nuclear envelope proteins and wheat germ agglutinin-bound fraction. Test sera were obtained from 175 patients with PBC and from 120 controls. Anti-gp210, anti-lamina associated polypeptide 2, anti-lamin B receptor, and anti-p62 complex antibodies were detected with a frequency of 26% (46 of 175), 6% (11 of 175), 9% (16 of 175), and 13% (15 of 115), respectively. The confirmation of Scheuer's stage IV was made with a frequency of 27% (4 of 15) in PBC patients with anti-p62 complex antibody, in contrast to only 2% (2 of 100) in PBC patients without anti-p62 complex antibody. This difference was found to be statistically significant. The presence of anti-p62 complex antibody may be related with the progressive or advanced state of PBC.

Animals↗
PubMed1996

Characterization of p92, karyopherin beta, co-purified with N-acetylglucosamine-bearing nucleoporins from rat liver nuclear envelopes.

A 92k protein (p92) was purified from the wheat germ agglutinin-Sepharose (WGA-Sepharose) bound fraction of a rat liver nuclear envelope salt-extract by DEAE-5PW and hydroxyapatite HPLCs. Partial amino acid sequence analysis of p92 revealed that it is karyopherin beta, which was found recently in the cytosolic fraction. It was shown using anti-p92 antiserum that the protein is present in the nuclear envelope and cytosolic fractions, in almost the same amounts, but not in other subcellular fractions of rat liver. p92 bound to N-acetylglucosamine bearing nucleoporins (GNPs) on WGA-Sepharose, but not directly to WGA. The amount of p92 found in the rat liver nuclear envelope fraction corresponded to about 10% of the nuclear pore complex in mass, and to as much as 140 mol of p92 per mol of nuclear pore complex. Hydrodynamic analysis of the purified p92 suggested that the molecule is present as a monomer and that it is a rod-shaped molecule. The interaction of p92 and GNPs seemed to be hydrophobic and ionic. Based on these results, the participation of nuclear envelope p92 in protein nuclear transport is discussed.

Acetylglucosamine↗
PubMed2001

Lamins in disease: why do ubiquitously expressed nuclear envelope proteins give rise to tissue-specific disease phenotypes?

The nuclear lamina is a filamentous structure composed of lamins that supports the inner nuclear membrane. Several integral membrane proteins including emerin, LBR, LAP1 and LAP2 bind to nuclear lamins in vitro and can influence lamin function and dynamics in vivo. Results from various studies suggest that lamins function in DNA replication and nuclear envelope assembly and determine the size and shape of the nuclear envelope. In addition, lamins also bind chromatin and certain DNA sequences, and might influence chromosome position. Recent evidence has revealed that mutations in A-type lamins give rise to a range of rare, but dominant, genetic disorders, including Emery-Dreifuss muscular dystrophy, dilated cardiomyopathy with conduction-system disease and Dunnigan-type familial partial lipodystrophy. An examination of how lamins A/C, emerin and other integral membrane proteins interact at the INM provides the basis for a novel model for how mutations that promote disease phenotypes are likely to influence these interactions and therefore cause cellular pathology through a combination of weakness of the lamina or altered gene expression.

Animals↗
PubMed1981

Nuclear envelope of the seminal-vesicle epithelium.

The nuclear envelope of seminal-vesicle epithelium was isolated by a procedure involving enzymic digestion with deoxyribonuclease I, sonication in the presence of 0.34 M-sodium citrate, and centrifugation through sucrose density gradients. The mass of envelope DNA was only 0.8% of that of envelope protein, and by transmission electron microscopy the envelope was 98-99% pure. We showed that the envelope possess a protein kinase activity which is uninfluenced by cyclic nucleotides. Both lysine-rich histone and dephosphophosvitin as substrates gave a greater specific activity than did envelope protein itself. Optimum requirements with respect to Na+, Mg2+, pH and ATP were established for each substrate, and the influence of other factors on enzyme activity was investigated. Data, obtained mainly with the use of lysine-rich histone, are presented which indicate that nuclear envelope from intact and 96 h-castrated guinea pigs may have equal protein kinase activities and, in separate experiments, equal phosphoprotein phosphatase activities. Clarification of these initial observations must await identification of the natural substrates or the envelope's phosphorylation-dephosphorylation reactions.

Animals↗
PubMed1990

Breakdown of the sperm nuclear envelope is a prerequisite for male pronucleus formation: direct evidence from the gynogenetic crucian carp Carassius auratus langsdorfii.

The gynogenetic fish, Carassius auratus langsdorfii (the ginbuna, a crucian carp), provides an interesting model for the study of the mechanisms controlling male pronucleus formation. When the sperm nucleus of a different subspecies (C. a. cuvieri) is incorporated into the gynogenetic egg, the nuclear envelope of the spermatozoon is not broken down, and the pronucleus fails to develop, although dispersion of the sperm chromatin occurs to some extent within the space limited by the nuclear envelope. When spermatozoa without plasma membranes and nuclear envelopes were microinjected into mature activated eggs, the sperm nuclei underwent chromatin dispersion, nuclear envelope formation, DNA synthesis, and transformation into male pronuclei. These results indicate that the failure of the male pronucleus to form in ginbuna is primarily due to the failure of sperm nuclear envelope breakdown. We conclude that sperm nuclear envelope breakdown is an indispensable step for the development of the male pronucleus.

Animals↗
PubMed1997

Sperm nuclear envelope: breakdown of intrinsic envelope and de novo formation in hamster oocytes or eggs.

During fertilisation of a fully mature oocyte, the sperm intrinsic nuclear envelope (SINE) disappears soon after sperm-oocyte fusion. A new nuclear envelope appears around the decondensed sperm chromatin when the oocyte reaches telophase II. Whether the SINE persists or rapidly disappears after sperm entry into immature oocytes or fertilised eggs has been controversial. Nuclear envelopes have been demonstrated around the sperm chromatin, which cannot be decondensed within the ooplasm of these oocytes or eggs, but whether these envelopes are persisting SINEs or newly formed envelopes has been a point of dispute. To resolve this issue, the fate of the SINEs of hamster sperm nuclei was traced after incorporation into immature oocytes at the germinal vesicle stage (GV oocytes) or fertilised eggs at the pronuclear stage (PN eggs). The SINEs disappeared quickly within these oocytes or eggs, like those within maturing or mature oocytes, suggesting that the envelopes around the sperm chromatin must be newly formed after SINE breakdown. To obtain further evidence, a detergent-treated, SINE-free sperm nucleus was injected into a PN egg. A new envelope appeared around the still-condensed or partially decondensed sperm chromatin within 3 h after injection. Thus, disassembly of the SINE within ooplasm, unlike that of nuclear envelopes of other cells at prophase, is independent of the cell cycle stage of the oocyte or egg, whereas the ability of the ooplasm to assemble the new envelope is restricted to certain periods of the cycle, i.e. early prophase and telophase during meiosis and interphase, periods when active M-phase promoting factor (MPF) is absent from the ooplasm.

Animals↗
PubMed1982

Binding of dihydrotestosterone to a nuclear-envelope fraction from the male rat liver.

Intact nuclear 'ghosts' containing small amounts of DNA were obtained from rat liver. Incubation of radiolabelled dihydrotestosterone with isolated nuclear-envelope fraction from male rat liver resulted in specific binding of the dihydrotestosterone to the membranes. Optimal binding occurred at 20 degrees C after 20h incubation. Storage for 2 weeks at -80 degrees C resulted in little loss of specific binding. Scatchard analysis revealed a class of binding sites with a KD of 23.2 nM. Pronase and heat treatment destroyed the binding site. Androgens and glucocorticoids competed for labelled dihydrotestosterone binding to the ghosts, whereas oestrogens did not compete. Castration 24h before preparation of ghosts did not alter the binding site, and a similar class of binding sites was identified on female rat liver nuclear envelopes.

Animals↗
PubMedDate not supplied

[Changes in composition of acid soluble proteins and DNA in chromatin of rat liver and brain bound and not bound to nuclear envelope as a function of age and under the influence of antioxidant ionol].

In two-day rat pups, the histone H1 content in the brain chromatin was higher than in the liver chromatin, as compared to histone of the nucleosome core. The H1 content in the brain chromatin decreased with the age, while in the liver chromatin it increased. At the same time, in the adult brain chromatin bound to the nuclear envelope, a high level of H1 characteristic of chromatin of the newborn rats was preserved, while in a similar chromatin of the adult liver, the H1 content increased, but still remained less than in the chromatin not bound to the nuclear envelope. In both organs, the composition and quantitation of H1 subfractions were different in chromatins bound and not bound to the nuclear envelope. The chromatin from the liver and brain bound to the nuclear envelope differed also in the composition and quantitation of minor acid soluble proteins. In the presence of the antioxidant ionol, the 5-methylcytosine content in DNA of chromatin of the rat liver bound to the nuclear envelope increased while in the chromatin not bound to the nuclear envelope, it remained unchanged. Thus the chromatins bound and not bound to the nuclear envelope differ in the composition and mount of acid soluble proteins, including histone H1, the contents of these proteins in bound and not bound chromatin are different and change with the age in different ways. The antioxidant ionol affects differently the methylation of bound and not bound chromatin.

Aging↗
PubMed1987

Lamin B constitutes an intermediate filament attachment site at the nuclear envelope.

We found that urea extraction of turkey erythrocyte nuclear envelopes abolished their ability to bind exogenous 125I-vimentin, while, at the same time, it removed the nuclear lamins from the membranes. After purification of the lamins from such urea extracts, a specific binding between isolated vimentin and lamin B, or a lamin A + B hetero-oligomer, was detected by affinity chromatography. Similar analysis revealed that the 6.6-kD vimentin tail piece was involved in this interaction. By other approaches (quantitative immunoprecipitation, rate zonal sedimentation, turbidometric assays) a substoichiometric lamin B-vimentin binding was determined under in vitro conditions. It was also observed that anti-lamin B antibodies but not other sera (anti-lamin A, anti-ankyrin, preimmune) were able to block 70% of the binding of 125I-vimentin to native, vimentin-depleted, nuclear envelopes. These data, which were confirmed by using rat liver nuclear lamins, indicate that intermediate filaments may be anchored directly to the nuclear lamina, providing a continuous network connecting the plasma membrane skeleton with the karyoskeleton of eukaryotic cells.

Animals↗
PubMed2000

Distinct ion channel classes are expressed on the outer nuclear envelope of T- and B-lymphocyte cell lines.

The outer nuclear membrane, endoplasmic reticulum, and mitochondrial membrane ion channels are poorly understood, although they are important in the control of compartmental calcium levels, cell division, and apoptosis. Few direct recordings of these ion channels have been made because of the difficulty of accessing these intracellular membranes. Using patch-clamp techniques on isolated nuclei, we measured distinct ion channel classes on the outer nuclear envelope of T-cell (human Jurkat) and BFL5 cell (murine promyelocyte) lines. We first imaged the nuclear envelopes of both Jurkat and FL5 cells with atomic force microscopy to determine the density of pore proteins. The nuclear pore complex was intact at roughly similar densities in both cell types. In patch-clamp recordings of Jurkat nuclear membranes, Cl channels (105 +/- 5 pS) predominated and inactivated with negative pipette potentials. Nucleotides transiently inhibited the anion channel. In contrast, FL5 nuclear channels were cation selective (52 +/- 2 pS), were inactivated with positive membrane potentials, and were insensitive to GTPgammaS applied to the bath. We hypothesize that T- and B-cell nuclear membrane channels are distinct, and that this is perhaps related to their unique roles in the immune system.

Animals↗
PubMed1978

Abnormalities of the nuclear envelope in porcine muscle affected with congenital myofibrillar hypoplasia.

The nuclear ultrastructure of muscle fibres in congenital myofibrillar hypoplasia of piglets was studied in order to provide more information on the pathological changes present. In the initial stages of the disease, muscle fibres with a small reduction of myofibrils often had an increased number of nuclear pores. In the more advanced stages of the disease, the following nuclear abnormalities were observed in muscle fibres showing an extensive disintegration of myofibrils: 1) large dilations of the perinuclear cisternae, 2) small nuclear protrusions projecting into these dilations and 3) appositions of stray membranes of the disrupted endoplasmic reticulum to the nuclear envelope. The increase in the number of nuclear pores may be significant in the development of pathological changes in congenital myofibrillar hypoplasia which is thought to be a hereditary disease. The observed abnormalities of the nuclear envelope appear to be characteristic for muscle fibres undergoing degeneration.

Animals↗
PubMed2000

Nuclear lamins A and B1: different pathways of assembly during nuclear envelope formation in living cells.

At the end of mitosis, the nuclear lamins assemble to form the nuclear lamina during nuclear envelope formation in daughter cells. We have fused A- and B-type nuclear lamins to the green fluorescent protein to study this process in living cells. The results reveal that the A- and B-type lamins exhibit different pathways of assembly. In the early stages of mitosis, both lamins are distributed throughout the cytoplasm in a diffusible (nonpolymerized) state, as demonstrated by fluorescence recovery after photobleaching (FRAP). During the anaphase-telophase transition, lamin B1 begins to become concentrated at the surface of the chromosomes. As the chromosomes reach the spindle poles, virtually all of the detectable lamin B1 has accumulated at their surfaces. Subsequently, this lamin rapidly encloses the entire perimeter of the region containing decondensing chromosomes in each daughter cell. By this time, lamin B1 has assembled into a relatively stable polymer, as indicated by FRAP analyses and insolubility in detergent/high ionic strength solutions. In contrast, the association of lamin A with the nucleus begins only after the major components of the nuclear envelope including pore complexes are assembled in daughter cells. Initially, lamin A is found in an unpolymerized state throughout the nucleoplasm of daughter cell nuclei in early G1 and only gradually becomes incorporated into the peripheral lamina during the first few hours of this stage of the cell cycle. In later stages of G1, FRAP analyses suggest that both green fluorescent protein lamins A and B1 form higher order polymers throughout interphase nuclei.

Anaphase↗
PubMed2006

Monitoring the permeability of the nuclear envelope during the cell cycle.

In animal organisms the nuclear envelope (NE) dis-assembles during cell division resulting in complete intermixing of cytoplasmic and nuclear compartments. This leads to the activation of many mitotic enzymes, which were kept away from their substrates or regulators by nuclear or cytoplasmic sequestration in interphase. Nuclear envelope breakdown (NEBD) is thus an essential step of mitotic entry and commits a cell to M-phase. NEBD begins with the partial disassembly of nuclear pore complexes, leading to a limited permeabilization of the NE for molecules up to approximately 40 nm diameter. This is followed by the complete disruption of nuclear pores, which causes local fenestration of the double nuclear membrane and subsequently breakdown of the entire NE structure. Here, we describe the use of different sized inert fluorescent tracer molecules to directly visualize these different steps of NEBD in live cells by fluorescence microscopy.

Animals↗
PubMed2004

Giardia lamblia: behavior of the nuclear envelope.

Giardia Lamblia is a flagellar parasite possessing the unusual morphology of bearing two nuclei. New morphological observations on trophozoites and encysting Giardia nuclei using routine transmission electron microscopy, freeze fracture and cytochemistry are presented. Nuclear pores of both nuclei in the same cells were assessed on freeze-fracture replicas from different cell cycle phases, and compared. These techniques showed that (1) both nuclei in the same cell are distinct in nuclear pore number and distribution; (2) nuclear pore complexes are frequently clustered in nuclear envelope domains; (3) dividing nuclei display very few nuclear pores; (4) few ribosomes are found on the outer nuclear envelope of the trophozoite form; (5) nuclear membranes present spots of closely apposed membranes, which are different from the typical diaphragm nuclear pore complexes; (6) in addition to the nuclear pores, membrane blebs are also present in the nuclear envelope; (7) encysting cells show intranuclear inclusions, morphologically similar to the ESV (encystation-specific vesicles) and to the ER membranes, which may be the result of nuclear envelope folding. It is proposed that the two nuclei in Giardia are dissimilar in morphology and activity.

Animals↗
PubMed1995

Mutational analyses of fs(1)Ya, an essential, developmentally regulated, nuclear envelope protein in Drosophila.

The fs(1)Ya protein (YA) is an essential, maternally encoded, nuclear lamina protein that is under both developmental and cell cycle control. A strong Ya mutation results in early arrest of embryos. To define the function of YA in the nuclear envelope during early embryonic development, we characterized the phenotypes of four Ya mutants alleles and determined their molecular lesions. Ya mutant embryos arrest with abnormal nuclear envelopes prior to the first mitotic division; a proportion of embryos from two leaky Ya mutants proceed beyond this but arrest after several abnormal divisions. Ya unfertilized eggs contain nuclei of different sizes and condensation states, apparently due to abnormal fusion of the meiotic products immediately after meiosis. Lamin is localized at the periphery of the uncondensed nuclei in these eggs. These results suggest that YA function is required during and after egg maturation to facilitate proper chromatin condensation, rather than to allow a lamin-containing nuclear envelope to form. Two leaky Ya alleles that partially complement have lesions at opposite ends of the YA protein, suggesting that the N- and C-termini are important for YA function and that YA might interact with itself either directly or indirectly.

Alleles↗
PubMed2001

Anti-nuclear envelope antibodies: Clinical associations.

OBJECTIVES: Characterization of the clinical associations and clinical implications of antibodies reacting with antigens of the nuclear envelope. METHODS: Description of an illustrative case and a MEDLINE search-assisted literature review of relevant cases. RESULTS: With indirect immunofluorescence, autoantibodies directed against various antigens of the nuclear envelope stain the nucleus in a ring-like (rim) pattern. Autoantibodies against 5 antigenic components of the nuclear envelope have been described: anti-gp210, p62, lamina, lamina-associated polypeptides, and lamin B receptor. Antibodies to antigens of the nuclear pore complex, such as gp210 and p62, are highly specific (> 95%) for primary biliary cirrhosis and may aid in the serologic diagnosis of this condition, especially in cases in which antimitochondrial antibodies are not detectable. In contrast, antilamin antibodies are not disease-specific but seem to be associated with lupus anticoagulant or anticardiolipin antibodies, antiphospholipid syndrome, thrombocytopenia, autoimmune liver diseases, and arthralgia. High-titered antilamin antibodies help to define a subset of lupus patients with antiphospholipid antibodies who are at a lower risk of developing thrombotic events. In addition, preliminary data suggest that the presence of antilamin antibodies may be helpful in the diagnosis of chronic fatigue syndrome. CONCLUSIONS: Each of the antibodies reacting with nuclear membrane antigens has its own spectrum of disease associations. RELEVANCE: Determination of anti-nuclear envelope antibody pattern by indirect immunofluorescence, with subsequent determination of the specific antibody, carries important diagnostic and prognostic implications in various autoimmune conditions.

Antibodies, Antinuclear↗
PubMed1995

The nuclear envelope prevents reinitiation of replication by regulating the binding of MCM3 to chromatin in Xenopus egg extracts.

BACKGROUND: A complex of MCM proteins is implicated in ensuring that DNA replicates only once in each cell cycle, by 'replication licensing'. The nuclear membrane is also implicated in replication licensing, but the relationship between the MCM proteins and the nuclear membrane is unclear. Here, we investigate the relationship between XMCM3 (a component of the Xenopus MCM complex), nuclear envelope permeability and the initiation of DNA replication once per cell cycle. RESULTS: Our results show that the nuclear envelope does not prevent the entry of XMCM3 into the nucleus, but that it does prevent the binding of XMCM3 to chromatin. We have also identified another component of the Xenopus MCM complex as a homologue of the Schizosaccharomyces pombe protein Cdc21. XMCM3 does not preferentially co-localize with sites of DNA replication. Instead, it is almost uniformly distributed on chromatin and is suddenly lost during replication. XMCM3 crosses intact nuclear membranes of G2-phase HeLa cells but cannot then bind to chromatin. Permeabilization of the nuclear envelope allows the binding of XMCM3 to G2-phase chromatin. We have therefore resolved replication licensing into two stages. The first requires the entry of a cytosolic 'loading factor' that is excluded by the nuclear membrane; subsequently, MCM3 can bind to chromatin in the presence or absence of a nuclear membrane, but only if the loading factor has gained access in the absence of the membrane. CONCLUSIONS: The Xenopus MCM complex contains homologues of yeast MCM2, MCM3, MCM5 and Cdc21 proteins. XMCM3 is displaced from chromatin during replication. The nuclear envelope allows entry of XMCM3 into the nucleus, but regulates its binding to chromatin; binding requires a loading factor which cannot cross the nuclear envelope. Based on these results we present a two-stage model for replication licensing.

Amino Acid Sequence↗