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Lim CR, Kimata Y, Ohdate H, Kokubo T, Kikuchi N, Horigome T, Kohno K. The Saccharomyces cerevisiae RuvB-like protein, Tih2p, is required for cell cycle progression and RNA polymerase II-directed transcription. J Biol Chem 2000; 275:22409-17. [PMID: 10787406 DOI: 10.1074/jbc.m001031200] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Two highly conserved RuvB-like putative DNA helicases, p47/TIP49b and p50/TIP49a, have been identified in the eukaryotes. Here, we study the function of Saccharomyces cerevisiae TIH2, which corresponds to mammalian p47/TIP49b. Tih2p is required for vegetative cell growth and localizes in the nucleus. Immunoprecipitation analysis revealed that Tih2p tightly interacts with Tih1p, the counterpart of mammalian p50/TIP49a, which has been shown to interact with the TATA-binding protein and the RNA polymerase II holoenzyme complex. Furthermore, the mutational study of the Walker A motif, which is required for nucleotide binding and hydrolysis, showed that this motif plays indispensable roles in the function of Tih2p. When a temperature-sensitive tih2 mutant, tih2-160, was incubated at the nonpermissive temperature, cells were rapidly arrested in the G(1) phase. Northern blot analysis revealed that Tih2p is required for transcription of G(1) cyclin and of several ribosomal protein genes. The similarities between the mutant phenotypes of tih2-160 and those of taf145 mutants suggest a role for TIH2 in the regulation of RNA polymerase II-directed transcription.
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Affiliation(s)
- C R Lim
- Research and Education Center for Genetic Information and the Division of Gene Function in Animals, Nara Institute of Science and Technology, 8916-5, Takayama, Ikoma, Nara 630-0101, Japan
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102
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Shafi R, Iyer SP, Ellies LG, O'Donnell N, Marek KW, Chui D, Hart GW, Marth JD. The O-GlcNAc transferase gene resides on the X chromosome and is essential for embryonic stem cell viability and mouse ontogeny. Proc Natl Acad Sci U S A 2000; 97:5735-9. [PMID: 10801981 PMCID: PMC18502 DOI: 10.1073/pnas.100471497] [Citation(s) in RCA: 600] [Impact Index Per Article: 25.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Nuclear and cytoplasmic protein glycosylation is a widespread and reversible posttranslational modification in eukaryotic cells. Intracellular glycosylation by the addition of N-acetylglucosamine (GlcNAc) to serine and threonine is catalyzed by the O-GlcNAc transferase (OGT). This "O-GlcNAcylation" of intracellular proteins can occur on phosphorylation sites, and has been implicated in controlling gene transcription, neurofilament assembly, and the emergence of diabetes and neurologic disease. To study OGT function in vivo, we have used gene-targeting approaches in male embryonic stem cells. We find that OGT mutagenesis requires a strategy that retains an intact OGT gene as accomplished by using Cre-loxP recombination, because a deletion in the OGT gene results in loss of embryonic stem cell viability. A single copy of the OGT gene is present in the male genome and resides on the X chromosome near the centromere in region D in the mouse spanning markers DxMit41 and DxMit95, and in humans at Xq13, a region associated with neurologic disease. OGT RNA expression in mice is comparably high among most cell types, with lower levels in the pancreas. Segregation of OGT alleles in the mouse germ line with ZP3-Cre recombination in oocytes reveals that intact OGT alleles are required for completion of embryogenesis. These studies illustrate the necessity of conditional gene-targeting approaches in the mutagenesis and study of essential sex-linked genes, and indicate that OGT participation in intracellular glycosylation is essential for embryonic stem cell viability and for mouse ontogeny.
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Affiliation(s)
- R Shafi
- The Howard Hughes Medical Institute, Glycobiology Research and Training Center, Department of Cellular and Molecular Medicine, 9500 Gilman Drive-0625, University of California San Diego, La Jolla, CA 92093, USA
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103
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Lubas WA, Hanover JA. Functional expression of O-linked GlcNAc transferase. Domain structure and substrate specificity. J Biol Chem 2000; 275:10983-8. [PMID: 10753899 DOI: 10.1074/jbc.275.15.10983] [Citation(s) in RCA: 249] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
O-GlcNAc transferase (OGT) modifies nuclear pore proteins and transcription factors. In Arabidopsis, the OGT homolog participates in the gibberellin signaling pathway. We and others have proposed that mammalian OGT is the terminal step in a glucose-sensitive signal transduction pathway that becomes disregulated in insulin resistance. To facilitate mutational analysis of OGT in the absence of competing endogenous activity, we expressed the 103-kDa human OGT in Escherichia coli. Kinetic parameters for the purified recombinant enzyme (K(m) = 1.2 microM for Nup 62; K(m) = 0.5 microM for UDP-GlcNAc) are nearly identical to purified mammalian OGT. Deletions in the highly conserved C terminus result in a complete loss of activity. The N-terminal tetratricopeptide repeat domain is required for optimal recognition of substrates. Removal of the first three tetratricopeptide repeats greatly reduces the O-GlcNAc addition to macromolecular substrates. However, this altered enzyme retains full activity against appropriate synthetic peptides. Autoglycosylation of OGT is augmented when the first six tetratricopeptide repeats are removed showing that these repeats are not required for catalysis. Given its proposed role in modulating insulin action, OGT may modify kinases involved in this signaling cascade. Among the many kinases tested, OGT glycosylates glycogen synthase kinase-3 and casein kinase II, two enzymes critical in the regulation of glycogen synthesis.
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Affiliation(s)
- W A Lubas
- Laboratory of Cell Biochemistry and Biology, NIDDK, National Institutes of Health, Bethesda, Maryland 20892, USA
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104
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Askjaer P, Bachi A, Wilm M, Bischoff FR, Weeks DL, Ogniewski V, Ohno M, Niehrs C, Kjems J, Mattaj IW, Fornerod M. RanGTP-regulated interactions of CRM1 with nucleoporins and a shuttling DEAD-box helicase. Mol Cell Biol 1999; 19:6276-85. [PMID: 10454574 PMCID: PMC84588 DOI: 10.1128/mcb.19.9.6276] [Citation(s) in RCA: 173] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/1999] [Accepted: 06/21/1999] [Indexed: 11/20/2022] Open
Abstract
CRM1 is an export receptor mediating rapid nuclear exit of proteins and RNAs to the cytoplasm. CRM1 export cargoes include proteins with a leucine-rich nuclear export signal (NES) that bind directly to CRM1 in a trimeric complex with RanGTP. Using a quantitative CRM1-NES cargo binding assay, significant differences in affinity for CRM1 among natural NESs are demonstrated, suggesting that the steady-state nucleocytoplasmic distribution of shuttling proteins could be determined by the relative strengths of their NESs. We also show that a trimeric CRM1-NES-RanGTP complex is disassembled by RanBP1 in the presence of RanGAP, even though RanBP1 itself contains a leucine-rich NES. Selection of CRM1-binding proteins from Xenopus egg extract leads to the identification of an NES-containing DEAD-box helicase, An3, that continuously shuttles between the nucleus and the cytoplasm. In addition, we identify the Xenopus homologue of the nucleoporin CAN/Nup214 as a RanGTP- and NES cargo-specific binding site for CRM1, suggesting that this nucleoporin plays a role in export complex disassembly and/or CRM1 recycling.
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Affiliation(s)
- P Askjaer
- Department of Gene Expression, Deutsches Krebsforschungszentrum, Heidelberg, Germany
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105
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Miller MW, Caracciolo MR, Berlin WK, Hanover JA. Phosphorylation and glycosylation of nucleoporins. Arch Biochem Biophys 1999; 367:51-60. [PMID: 10375398 DOI: 10.1006/abbi.1999.1237] [Citation(s) in RCA: 76] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The nuclear pore complex mediates macromolecular transport between the nucleus and cytoplasm. Many nuclear pore components (nucleoporins) are modified by both phosphate and O-linked N-acetylglucosamine (O-GlcNAc). Among its many functions, protein phosphorylation plays essential roles in cell cycle progression. The role of O-GlcNAc addition is unknown. Here, levels of nucleoporin phosphorylation and glycosylation during cell cycle progression are examined. Whereas nuclear pore glycoproteins are phosphorylated in a cell-cycle-dependent manner, levels of O-GlcNAc remain constant. The major nucleoporin p62 can be phosphorylated in vitro by protein kinase A and glycogen synthase kinase (GSK)-3alpha but not by cyclin B/cdc2 or GSK-3beta. The consensus sites of these kinases resemble sites which can be glycosylated by O-GlcNAc transferase. These data are consistent with a model that O-GlcNAc limits nucleoporin hyperphosphorylation during M-phase and hastens the resumption of regulated nuclear transport at the completion of cell division.
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Affiliation(s)
- M W Miller
- Department of Biological Sciences, Wright State University, Dayton, Ohio, 45435-0001, USA.
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106
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Griffith LS, Schmitz B. O-linked N-acetylglucosamine levels in cerebellar neurons respond reciprocally to pertubations of phosphorylation. EUROPEAN JOURNAL OF BIOCHEMISTRY 1999; 262:824-31. [PMID: 10411645 DOI: 10.1046/j.1432-1327.1999.00439.x] [Citation(s) in RCA: 84] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The novel intracellular carbohydrate O-linked N-acetylglucosamine (O-GlcNAc) is present on proteins ranging from those of viruses to those of humans and include cytosolic, nuclear and plasma-membrane proteins. In this report we have examined the effect of manipulation of phosphorylation on the levels of O-GlcNAc in cerebellar neurons from early postnatal mice. Our results indicate a reciprocal response of O-GlcNAc levels to phosphorylation. Activation of protein kinase A or C, for example, results in reduced levels of O-GlcNAc specifically in the fraction of cytoskeletal and cytoskeleton-associated proteins, while inhibition of the same kinases results in increased levels of O-GlcNAc. These data are in keeping with a reciprocal action of O-GlcNAc with respect to phosphorylation and suggest that this modification may have a role in signal transduction.
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Affiliation(s)
- L S Griffith
- Department of Biochemistry, Institute for Animal Anatomy and Physiology, University of Bonn, Germany
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107
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Sutovsky P, Simerly C, Hewitson L, Schatten G. Assembly of nuclear pore complexes and annulate lamellae promotes normal pronuclear development in fertilized mammalian oocytes. J Cell Sci 1998; 111 ( Pt 19):2841-54. [PMID: 9730977 DOI: 10.1242/jcs.111.19.2841] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
In addition to functional nuclear pore complexes engaged in nucleo-cytoplasmic transport, the cytoplasmic stacks of pore complexes, called annulate lamellae, exist in numerous cell types. Although both annulate lamellae and nuclear pore complexes are present in fertilized mammalian oocytes, their relative roles in the process of fertilization and preimplantation development are not known. Using epifluorescence and electron microscopy, we explored their fate during bovine fertilization. The assembly of annulate lamellae in bovine oocytes was triggered by sperm-oocyte binding and continued concomitantly with the incorporation of the nuclear pores in the nuclear envelopes of the developing male and female pronuclei. This process was also induced by the parthenogenetic activation of metaphase-II-arrested oocytes. Depletion of Ca2+, previously implicated in oocyte activation and in the insertion of pore complexes into the nuclear envelope, prevented the formation of nuclear pore complexes, but not the assembly of annulate lamellae in oocyte cytoplasm. Injection of the nuclear pore antagonist, wheat germ agglutinin, into the cytoplasm of mature oocytes that were subsequently fertilized caused the arrest of pronuclear development, indicating the requirement of nuclear pore complexes for normal pronuclear development. Treatment of the fertilized oocytes with the microtubule inhibitor, nocodazole, prevented gathering of annulate lamellae around the developing pronuclei, insertion of nuclear pores into their nuclear envelopes, and further pronuclear development. The formation of the male pronuclei was reconstituted in Xenopus egg extracts and reflected the behavior of nuclear pores during natural fertilization. These data suggest that nuclear pore complexes are required for normal pronuclear development from its beginning up until pronuclear apposition. Annulate lamellae may be involved in the turnover of nuclear pore complexes during fertilization, which is in turn facilitated by the reorganization of oocyte microtubules and influx of Ca2+ into oocyte cytoplasm.
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Affiliation(s)
- P Sutovsky
- Departments of Obstetrics and Gynecology, and Cell and Developmental Biology, Oregon Health Sciences University, Portland, Oregon, USA
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108
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Abstract
Many nuclear and cytosolic proteins are modified by single residues of O-linked N-acetyl-D-glucosamine. These include many proteins found in nuclear pore complexes required for transport of macromolecules between the nucleus and the cytoplasm. The best characterized pore glycoprotein, p62, mediates its function as one component of a protein complex essential for nuclear transport. Although p62 sugar residues are not essential for nuclear transport, they appear to oppose protein phosphorylation occurring at sites predicted to destabilize protein-protein interactions of the p62 complex. Recently, a p62-like protein isolated from mouse neuroblastoma cells was reported to be modified by both GlcNAc and sialic acid. As there is little precedent for nucleoplasmic sialation, the finding that a characterized nuclear pore protein is sialated is significant because it may regulate pore function. To assess the biological importance of p62 sialation, GlcNAc and sialic acid-specific lectins were used to examine the state of p62 glycosylation in cells commonly used to study nuclear transport: frog eggs and normal rat kidney and HeLa fibroblasts. In addition, four mouse neuroblastoma cell lines derived from the same tumor were examined. The glycosylation of p62 in these cells appears to involve only single O-linked GlcNAc moieties; no significant sialation was detected.
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Affiliation(s)
- B Fang
- Department of Biological Sciences, Wright State University, Dayton, Ohio, 45435-0001, USA
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109
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Previato JO, Sola-Penna M, Agrellos OA, Jones C, Oeltmann T, Travassos LR, Mendonça-Previato L. Biosynthesis of O-N-acetylglucosamine-linked glycans in Trypanosoma cruzi. Characterization of the novel uridine diphospho-N-acetylglucosamine:polypeptide N-acetylglucosaminyltransferase-catalyzing formation of N-acetylglucosamine alpha1-->O-threonine. J Biol Chem 1998; 273:14982-8. [PMID: 9614105 DOI: 10.1074/jbc.273.24.14982] [Citation(s) in RCA: 62] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
In this study, we have characterized the activity of a uridine diphospho-N-acetylglucosamine:polypeptide-alpha-N-acetylglucosaminylt ransferase (O-alpha-GlcNAc-transferase) from Trypanosoma cruzi. The activity is present in microsomal membranes and is responsible for the addition of O-linked alpha-N-acetylglucosamine to cell surface proteins. This preparation adds N-acetylglucosamine to a synthetic peptide KPPTTTTTTTTKPP containing the consensus threonine-rich dodecapeptide encoded by T. cruzi MUC gene (Di Noia, J. M., Sánchez D. O., and Frasch, A. C. C. (1995) J. Biol. Chem. 270, 24146-24149). Incorporation of N-[3H]acetylglucosamine is linearly dependent on incubation time and concentration of enzyme and substrate. The transferase activity has an optimal pH of 7.5- 8.5, requires Mn2+, is unaffected by tunicamycin or amphomycin, and is strongly inhibited by UDP. The optimized synthetic peptide acceptor for the cytosolic O-GlcNAc-transferase (YSDSPSTST) (Haltiwanger, R. S., Holt, G. D., and Hart, G. W. (1990) J. Biol. Chem. 265, 2563-2568) is not a substrate for this enzyme. The glycosylated KPPTTTTTTTTKPP product is susceptible to base-catalyzed beta-elimination, and the presence of N-acetylglucosamine alpha-linked to threonine is supported by enzymatic digestion and nuclear magnetic resonance data. These results describe a unique biosynthetic pathway for T. cruzi surface mucin-like molecules, with potential chemotherapeutic implications.
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Affiliation(s)
- J O Previato
- Instituto de Microbiologia, CCS-Bloco I, Universidade Federal do Rio de Janeiro, 21944 970 Cidade Universitária, Rio de Janeiro-RJ, Brazil
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110
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Kehlenbach RH, Dickmanns A, Gerace L. Nucleocytoplasmic shuttling factors including Ran and CRM1 mediate nuclear export of NFAT In vitro. J Cell Biol 1998; 141:863-74. [PMID: 9585406 PMCID: PMC2132762 DOI: 10.1083/jcb.141.4.863] [Citation(s) in RCA: 144] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/1998] [Revised: 04/03/1998] [Indexed: 02/07/2023] Open
Abstract
We have developed a permeabilized cell assay to study the nuclear export of the shuttling transcription factor NFAT, which contains a leucine-rich export signal. The assay uses HeLa cells that are stably transfected with NFAT fused to the green fluorescent protein (GFP). Nuclear export of GFP-NFAT in digitonin-permeabilized cells occurs in a temperature- and ATP-dependent manner and can be quantified by flow cytometry. In vitro NFAT export requires the GTPase Ran, which is released from cells during the digitonin permeabilization. At least one additional rate-limiting export factor is depleted from permeabilized cells by a preincubation at 30 degrees C in the absence of cytosol. This activity can be provided by cytosolic or nucleoplasmic extracts in a subsequent export step. Using this assay, we have purified a second major export activity from cytosol. We found that it corresponds to CRM1, a protein recently reported to be a receptor for certain leucine-rich export sequences. CRM1 appears to be imported into the nucleus by a Ran-dependent mechanism that is distinct from conventional signaling pathways. Considered together, our studies directly demonstrate by fractionation and reconstitution that nuclear export of NFAT is mediated by multiple nucleocytoplasmic shuttling factors, including Ran and CRM1.
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Affiliation(s)
- R H Kehlenbach
- Department of Cell Biology and Department of Molecular Biology, The Scripps Research Institute, La Jolla, California 92037, USA
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111
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Kollár R, Reinhold BB, Petráková E, Yeh HJ, Ashwell G, Drgonová J, Kapteyn JC, Klis FM, Cabib E. Architecture of the yeast cell wall. Beta(1-->6)-glucan interconnects mannoprotein, beta(1-->)3-glucan, and chitin. J Biol Chem 1997; 272:17762-75. [PMID: 9211929 DOI: 10.1074/jbc.272.28.17762] [Citation(s) in RCA: 390] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
In a previous study (Kollár, R., Petráková, E., Ashwell, G., Robbins, P. W., and Cabib, E. (1995) J. Biol. Chem. 270, 1170-1178), the linkage region between chitin and beta(1-->3)-glucan was solubilized and isolated in the form of oligosaccharides, after digestion of yeast cell walls with beta(1-->3)-glucanase, reduction with borotritide, and subsequent incubation with chitinase. In addition to the oligosaccharides, the solubilized fraction contained tritium-labeled high molecular weight material. We have now investigated the nature of this material and found that it represents areas in which all four structural components of the cell wall, beta(1-->3)-glucan, beta(1-->6)-glucan, chitin, and mannoprotein are linked together. Mannoprotein, with a protein moiety about 100 kDa in apparent size, is attached to beta(1-->6)-glucan through a remnant of a glycosylphosphatidylinositol anchor containing five alpha-linked mannosyl residues. The beta(1-->6)-glucan has some beta(1-->3)-linked branches, and it is to these branches that the reducing terminus of chitin chains appears to be attached in a beta(1-->4) or beta(1-->2) linkage. Finally, the reducing end of beta(1-->6)-glucan is connected to the nonreducing terminal glucose of beta(1-->3)-glucan through a linkage that remains to be established. A fraction of the isolated material has three of the main components but lacks mannoprotein. From these results and previous findings on the linkage between mannoproteins and beta(1-->6)-glucan, it is concluded that the latter polysaccharide has a central role in the organization of the yeast cell wall. The possible mechanism of synthesis and physiological significance of the cross-links is discussed.
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Affiliation(s)
- R Kollár
- Laboratory of Biochemistry and Metabolism, NIDDK, Bethesda, Maryland 20892, USA
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112
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Rutherford SA, Goldberg MW, Allen TD. Three-dimensional visualization of the route of protein import: the role of nuclear pore complex substructures. Exp Cell Res 1997; 232:146-60. [PMID: 9141631 DOI: 10.1006/excr.1997.3487] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
The three-dimensional localization of nucleoplasmin and wheat germ agglutinin (WGA) at the nuclear envelope of Xenopus oocytes is demonstrated by microinjecting protein coated gold colloids and examining their distribution using both stereo transmission electron microscopy and field emission in-lens scanning electron microscopy. Localization of many WGA gold particles and nucleoplasmin gold particles at the same nuclear pore complex (NPC) following coinjection is demonstrated. Binding of the WGA gold in the central region of the NPCs appears to form a barrier, preventing the import of nucleoplasmin gold, and includes central localization along radial "tracks" which correspond to the internal filaments connecting the cytoplasmic ring and the central region of the NPC. We suggest that these filaments may in some way be involved in opening and closing of the central channel of the NPC for transport. Transport of nucleoplasmin through the central region of the NPCs appears to be in "single file" regardless of the size of the colloidal gold, and distribution into the nucleoplasm appears to be through the basket rings with no association of the nucleoplasmin gold with the basket filaments being observed.
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Affiliation(s)
- S A Rutherford
- CRC Department of Structural Cell Biology, Paterson Institute for Cancer Research, Christie Hospital NHS Trust, Manchester, United Kingdom
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113
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Lubas WA, Frank DW, Krause M, Hanover JA. O-Linked GlcNAc transferase is a conserved nucleocytoplasmic protein containing tetratricopeptide repeats. J Biol Chem 1997; 272:9316-24. [PMID: 9083068 DOI: 10.1074/jbc.272.14.9316] [Citation(s) in RCA: 406] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
O-Linked GlcNAc addition and phosphorylation may compete for sites on nuclear pore proteins and transcription factors. We sequenced O-linked GlcNAc transferase from rabbit blood and identified the homologous Caenorhabditis elegans transferase gene on chromosome III. We then isolated C. elegans and human cDNAs encoding the transferase. The enzymes from the two species appear to be highly conserved; both contain multiple tetratricopeptide repeats and nuclear localization sequences. The C. elegans transferase accumulated in the nucleus and in perinuclear aggregates in overexpressing transgenic lines. O-Linked GlcNAc transferase activity was also elevated in HeLa cells transfected with the human cDNA. At least four human transcripts were observed in the tissues examined ranging in size from 4.4 to 9.3 kilobase pairs. The two largest transcripts (7.9 and 9.3 kilobase pairs) were enriched at least 12-fold in the pancreas. Based on its substrate specificity and molecular features, we propose that O-linked GlcNAc transferase is part of a glucose-responsive pathway previously implicated in the pathogenesis of diabetes mellitus.
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Affiliation(s)
- W A Lubas
- Laboratory of Cell Biochemistry and Biology, NIDDK, National Institutes of Health, Bethesda, Maryland 20892, USA
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114
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Haltiwanger RS, Busby S, Grove K, Li S, Mason D, Medina L, Moloney D, Philipsberg G, Scartozzi R. O-glycosylation of nuclear and cytoplasmic proteins: regulation analogous to phosphorylation? Biochem Biophys Res Commun 1997; 231:237-42. [PMID: 9070256 DOI: 10.1006/bbrc.1997.6110] [Citation(s) in RCA: 77] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Affiliation(s)
- R S Haltiwanger
- Department of Biochemistry and Cell Biology, State University of New York at Stony Brook 11794-5215, USA
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115
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Jiang MS, Hart GW. A subpopulation of estrogen receptors are modified by O-linked N-acetylglucosamine. J Biol Chem 1997; 272:2421-8. [PMID: 8999954 DOI: 10.1074/jbc.272.4.2421] [Citation(s) in RCA: 63] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Estrogen receptors (ER) are ligand-inducible transcription factors regulated by Ser(Thr)-O-phosphorylation. Many transcription factors and eukaryotic RNA polymerase II itself are also dynamically modified by Ser(Thr)-O-linked N-acetylglucosamine moieties (O-GlcNAc). Here we report that subpopulations of murine, bovine, and human estrogen receptors are modified by O-GlcNAc. O-GlcNAc moieties were detected on insect cell-expressed, mouse ER (mER) by probing with bovine milk galactosyltransferase, followed by structural analysis. Wheat germ agglutinin-Sepharose affinity chromatography also readily detected terminal GlcNAc residues on subpopulations of ER purified from calf uterus, from human breast cancer cells (MCF-7), or from mER produced by in vitro translation. These data suggest that greater than 10% of these populations of estrogen receptors bear O-GlcNAc. Site mapping of insect cell expressed mER localized one major site of O-GlcNAc addition to Thr-575, within a PEST region of the carboxyl-terminal F domain. Based upon their relative resistance to both hexosaminidase and to in vitro galactosylation, O-GlcNAc moieties appear to be largely buried on native mER. This dynamic saccharide modification, like phosphorylation, may play a role in modulating the dimerization, stability, or transactivation functions of estrogen receptors.
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Affiliation(s)
- M S Jiang
- Department of Biological Chemistry, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA
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116
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Abstract
Modification of Ser and Thr residues by attachment of O-linked N-acetylglucos-amine [Ser(Thr)-O-GlcNAcylation] to eukaryotic nuclear and cytosolic proteins is as dynamic and possibly as abundant as Ser(Thr) phosphorylation. Known O-GlcNAcylated proteins include cytoskeletal proteins and their regulatory proteins; viral proteins; nuclear-pore, heat-shock, tumor-suppressor, and nuclearoncogene proteins; RNA polymerase II catalytic subunit; and a multitude of transcription factors. Although functionally diverse, all of these proteins are also phosphoproteins. Most O-GlcNAcylated proteins form highly regulated multimeric associations that are dependent upon their posttranslational modifications. Evidence is mounting that O-GlcNAcylation is an important regulatory modification that may have a reciprocal relationship with O-phosphorylation and may modulate many biological processes in eukaryotes.
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Affiliation(s)
- G W Hart
- Department of Biochemistry and Molecular Genetics, University of Alabama at Birmingham, School of Medicine 35294-0005, USA.
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117
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Emig S, Schmalz D, Shakibaei M, Buchner K. The nuclear pore complex protein p62 is one of several sialic acid-containing proteins of the nuclear envelope. J Biol Chem 1995; 270:13787-93. [PMID: 7775435 DOI: 10.1074/jbc.270.23.13787] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
While investigating the glycosylation of nuclear envelope proteins of neuroblastoma cells, we found several proteins that bound the sialic acid-specific Sambucus nigra agglutinin. The strongest signals were obtained for proteins with apparent molecular masses of 66 and 180 kDa. The specificity of the lectin binding was checked by acylneuraminyl hydrolase treatment of nuclear envelope proteins, which prohibited S. nigra agglutinin binding. Digestion of nuclear envelope proteins with the N-glycosidase F revealed that sialic acid was N-glycosidically linked to the 180-kDa protein and very probably O-glycosidically linked to the 66-kDa protein. Upon extraction, the latter behaved like the nucleoporin p62 in that it was partly extracted by high ionic strength buffers, could not be solubilized by nonionic detergent, and was completely removed from the nuclear envelope with urea. Two-dimensional gel electrophoretic comparison showed that the S. nigra agglutinin-binding protein and p62 have an identical isoelectric point of about 5.0 and an identical apparent molecular mass of 66 kDa. This, together with the binding of the anti-nucleoporin antibody, demonstrated the identity of the 66-kDa sialoprotein and p62. S. nigra agglutinin inhibits nuclear protein transport in neuroblastoma cells, strongly suggesting a functional significance of sialylation of p62.
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Affiliation(s)
- S Emig
- Arbeitsgruppe Neurochemie, Institut für Biochemie, Freie Universität Berlin, Federal Republic of Germany
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118
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Callaerts P, Vulsteke V, Loof A, Peumans W. Lectin binding sites during Drosophila embryogenesis. ACTA ACUST UNITED AC 1995; 204:229-243. [DOI: 10.1007/bf00208490] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/1994] [Accepted: 07/28/1994] [Indexed: 01/20/2023]
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119
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Macaulay C, Meier E, Forbes DJ. Differential mitotic phosphorylation of proteins of the nuclear pore complex. J Biol Chem 1995; 270:254-62. [PMID: 7814383 DOI: 10.1074/jbc.270.1.254] [Citation(s) in RCA: 169] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
During each cell cycle, the nucleus of higher eukaryotes undergoes a dramatic assembly and disassembly. These events can be faithfully reproduced in vitro using cell-free extracts derived from Xenopus eggs. Such extracts contain three major N-acetylglucosaminylated proteins, p200, p97, and p60. All three become assembled into reconstituted nuclear pores. Here we show that p200, p97, and p60 exist in eggs in soluble high molecular mass complexes of 1000, 450, and 600 kDA, respectively. The bulk of p60 is stably associated with proteins of 58 and 54 kDa, while p200 is associated with a fraction of p60 in a separate complex lacking p58 and p54. Upon examining the behavior of these proteins in the cell cycle, we find that p200 and p97 are highly phosphorylated at mitosis, both in vivo and in vitro. Moreover, in extracts that cycle between interphase and mitosis, p200 and p97 are specifically phosphorylated at mitosis. Corresponding with their mitotic phosphorylation, both p200 and p97 are specific substrates for purified mitotic Cdc2 kinase, whereas nucleoporin p60 is not. Analysis indicates that the size of the complexes containing the pore N-acetylglucosamine glycoproteins does not change during mitosis, suggesting that such complexes represent stable multicomponent modules into which the nucleus disassembles at mitosis.
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Affiliation(s)
- C Macaulay
- Department of Biology, University of California at San Diego, La Jolla 92093-0347
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120
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The Sequestration of mRNA in the Cytoskeleton and Other Subcellular Structures. Cytoskeleton (Hoboken) 1995. [DOI: 10.1016/s1569-2558(08)60259-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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121
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Clathrin assembly protein AP-3 is phosphorylated and glycosylated on the 50-kDa structural domain. J Biol Chem 1994. [DOI: 10.1016/s0021-9258(17)31968-3] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
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122
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Radu A, Blobel G, Wozniak R. Nup107 is a novel nuclear pore complex protein that contains a leucine zipper. J Biol Chem 1994. [DOI: 10.1016/s0021-9258(17)32483-3] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
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123
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Lipińska A, Włodarczyk MM, Gaczyński M, Krześlak A. Lectin-binding glycoproteins in nuclear fractions from hamster liver and Kirkman-Robbins hepatoma. COMPARATIVE BIOCHEMISTRY AND PHYSIOLOGY. BIOCHEMISTRY AND MOLECULAR BIOLOGY 1994; 108:199-207. [PMID: 8055186 DOI: 10.1016/0305-0491(94)90066-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
As a further step toward characterizing the major nuclear glycoproteins from hamster liver and Kirkman-Robbins hepatoma (Lipińska A. and Gaczyński M. Int. J. Biochem. 4, 1385-1390, 1992) its intranuclear localization was studied. The glycoprotein patterns of examined nuclear fractions of hamster liver and hepatoma revealed some cell specificity observed especially in nuclear matrix preparations. Our results show the extensive presence of envelope glycoproteins in the nuclear matrix.
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Affiliation(s)
- A Lipińska
- Department of Cytobiochemistry, University of Lódź, Poland
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124
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Miller M, Hanover J. Functional nuclear pores reconstituted with beta 1-4 galactose-modified O-linked N-acetylglucosamine glycoproteins. J Biol Chem 1994. [DOI: 10.1016/s0021-9258(17)37106-5] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
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125
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Affiliation(s)
- L S Cox
- Department of Biochemistry, University of Dundee, Scotland
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126
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Roquemore EP, Chou TY, Hart GW. Detection of O-linked N-acetylglucosamine (O-GlcNAc) on cytoplasmic and nuclear proteins. Methods Enzymol 1994; 230:443-60. [PMID: 8139512 DOI: 10.1016/0076-6879(94)30028-3] [Citation(s) in RCA: 120] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Affiliation(s)
- E P Roquemore
- Department of Biochemistry and Molecular Genetics, School of Medicine, University of Alabama at Birmingham 35294
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127
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Chugani DC, Rome LH, Kedersha NL. Evidence that vault ribonucleoprotein particles localize to the nuclear pore complex. J Cell Sci 1993; 106 ( Pt 1):23-9. [PMID: 8270627 DOI: 10.1242/jcs.106.1.23] [Citation(s) in RCA: 145] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Vaults are cytoplasmic ribonucleoprotein organelles that are highly conserved among diverse eukaryotic species. Their mass (12.9 MDa), diameter (26-35 nm) and shape (two halves, each with eightfold radial symmetry) have recently been determined and are similar to those ascribed to the central plug (or transporter) of the nuclear pore complex (NPC). The size and eightfold symmetry of the vault particle make it conducive to interacting physically in a complementary manner with NPCs. The present study demonstrates that vaults specifically associate with nuclei by both immunoblotting and immunofluorescence. Immunogold EM confirmed that vaults associate with the nuclear envelope in tissue sections and with NPCs of isolated nuclei.
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Affiliation(s)
- D C Chugani
- Department of Pharmacology, UCLA School of Medicine 90024
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128
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Park PC, De Boni U. Nuclear membrane modifications in polytene nuclei of Drosophila melanogaster: serial reconstruction and cytochemistry. Anat Rec (Hoboken) 1992; 234:15-26. [PMID: 1416094 DOI: 10.1002/ar.1092340103] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
The nuclear envelope of polytene nuclei of salivary glands of Drosophila melanogaster displays modifications consisting of nuclear envelope invaginations (NEI) and evaginations (NEE). Ultrastructural analyses combined with three-dimensional reconstruction and cytochemistry show that NEI are bounded by a single membrane and that they may arise as invaginations of the inner nuclear membrane. NEI extend deeply into the nucleus. The lumens of NEI may collapse resulting in membranous sheets which may combine with those arising from adjacent NEI to form intranuclear structures resembling annulate lamellae. All NEI are associated with NEE. In contrast to NEI, NEE are enclosed in a double membrane morphologically identical to the nuclear envelope. While NEI and NEE share wheat germ agglutinin binding properties with the nuclear envelope, they differ in their ability to localize lanthanum. Pore annuli of NEI display complete lack of lanthanum binding, while those of NEE exhibit minor deposition of this cation. In contrast, pore annuli of the nuclear envelope are specifically and significantly decorated by lanthanum. A conceptual model based on the results obtained suggests that NEI are formed by invaginations of the inner nuclear membrane, together with accompanying modifications of pore complexes.
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Affiliation(s)
- P C Park
- Department of Physiology, Faculty of Medicine, University of Toronto, Ontario, Canada
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129
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Lipińska A, Gaczyński M. Nuclear glycoproteins of hamster liver and Kirkman-Robbins hepatoma recognized by concanavalin A. THE INTERNATIONAL JOURNAL OF BIOCHEMISTRY 1992; 24:1385-90. [PMID: 1426520 DOI: 10.1016/0020-711x(92)90063-7] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
1. Glycoproteins recognized by Concanavalin A (ConA) have been identified in nuclei and nuclear fractions differing in sensitivity to micrococcal nuclease digestion from hamster liver and Kirkman-Robbins hepatoma. 2. The major ConA binding proteins from hamster liver and Kirkman-Robbins hepatoma nuclei have molecular weights about 27,000 and 57,000, and 38,000 and 49,000, respectively. 3. A distinct distribution of glycoproteins between fractions differing in sensitivity to nuclease digestion has not been observed.
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Affiliation(s)
- A Lipińska
- Department of Cytobiochemistry, University of Lódź, Poland
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130
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Abstract
Nuclear pores are huge macromolecular assemblies, approximately 120 nm in diameter, that perforate the nuclear membrane and mediate nucleocytoplasmic transport. Nuclear pores are constructed from a cylindrical spoke-plug complex sandwiched between nucleoplasmic and cytoplasmic rings. The spoke-plug complex has pronounced 8-fold rotational symmetry, which is also present in the rings. Nucleocytoplasmic transport is an energy-requiring process that takes place through the centre of the pores and can accommodate particles up to about 25 nm diameter. Translocation is preceded by a separate binding step which does not require energy. Several nuclear pore proteins have been isolated and characterized. Many of these proteins contain O-linked N-acetyl glucosamine residues and may have similar modular domain structures.
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Affiliation(s)
- M Stewart
- MRC Laboratory of Molecular Biology, Cambridge, UK
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131
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Schröder HC, Facy P, Monsigny M, Pfeifer K, Bek A, Müller WE. Purification of a glucose-binding protein from rat liver nuclei. Evidence for a role in targeting of nuclear mRNP to nuclear pore complex. EUROPEAN JOURNAL OF BIOCHEMISTRY 1992; 205:1017-25. [PMID: 1576987 DOI: 10.1111/j.1432-1033.1992.tb16869.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
A nuclear carbohydrate-binding protein with a molecular mass of 67 kDa (CBP67), which is specific for glucose residues, was purified to essential homogeneity from rat liver nuclear extracts. This protein could also be isolated from nuclear ribonucleoprotein (RNP) complexes by extraction in the presence of 0.6 M or 2 M NaCl, but it was absent in polysomal RNP complex. The binding of the purified protein, which has an isoelectric point of 7.3, to glucose-containing glycoconjugates depends on the presence of Ca2+ and Mg2+. Using closed nuclear envelope vesicles as a system to study nuclear transport of RNA, it was shown that both entrapped polysomal mRNA and nuclear RNA precursors are readily exported from the vesicles in an ATP-dependent manner. The transport was unidirectional and strongly promoted by the poly(A) segment attached to these RNAs. In contrast, nuclear RNP complexes entrapped into the vesicles together with glucose-conjugated bovine serum albumin or nucleoplasmin, or bird nest glycoprotein, were not exported into the extravesicular space. However, transport of nuclear RNP complexes could be achieved in the presence of glucose or after co-addition of a glucose-recognizing lectin from Pellina semitubulosa. In Western blots, radioiodinated CBP67 binds to an 80-kDa polypeptide both in isolated rat liver nuclear envelopes and pore-complex laminae. From these results we postulate that CBP67 may direct nuclear RNP complexes to the nuclear pore.
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Affiliation(s)
- H C Schröder
- Institut für Physiologische Chemie, Universität Mainz, Federal Republic of Germany
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132
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Haltiwanger R, Blomberg M, Hart G. Glycosylation of nuclear and cytoplasmic proteins. Purification and characterization of a uridine diphospho-N-acetylglucosamine:polypeptide beta-N-acetylglucosaminyltransferase. J Biol Chem 1992. [DOI: 10.1016/s0021-9258(19)50380-5] [Citation(s) in RCA: 119] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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133
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Kessel RG. Annulate lamellae: a last frontier in cellular organelles. INTERNATIONAL REVIEW OF CYTOLOGY 1992; 133:43-120. [PMID: 1374369 DOI: 10.1016/s0074-7696(08)61858-6] [Citation(s) in RCA: 128] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Affiliation(s)
- R G Kessel
- Department of Biology, University of Iowa, Iowa City 52242
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134
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Abstract
Proteins targeted to specific intracellular organelles such as mitochondria or the endoplasmic reticulum are able to cross membranes. Yet, to enter or exit the nucleus, proteins and RNA must pass through nonmembranous "gates" of the nuclear envelope, the nuclear pore complexes. Recently, the primary amino acid sequence of a few nuclear pore proteins (the nucleoporins) became available. Nucleoporins from mammals, amphibians and yeast are structurally homologous indicating that nuclear pore structures are evolutionarily conserved in the eukaryotic cell. The role of nucleoporins in nucleocytoplasmic transport is still unclear: are nucleoporins involved in decoding nuclear targeting signals or are they mere transporters? Although definite answers are not yet available, data are rapidly accumulating from several laboratories using a variety of approaches.
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135
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Affiliation(s)
- H J Worman
- Department of Medicine, Mount Sinai School of Medicine, New York, New York 10029
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136
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137
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Garcia-Bustos J, Heitman J, Hall MN. Nuclear protein localization. BIOCHIMICA ET BIOPHYSICA ACTA 1991; 1071:83-101. [PMID: 2004116 DOI: 10.1016/0304-4157(91)90013-m] [Citation(s) in RCA: 457] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Affiliation(s)
- J Garcia-Bustos
- Department of Biochemistry, University of Basel, Switzerland
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138
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Soulard M, Barque JP, Della Valle V, Hernandez-Verdun D, Masson C, Danon F, Larsen CJ. A novel 43-kDa glycoprotein is detected in the nucleus of mammalian cells by autoantibodies from dogs with autoimmune disorders. Exp Cell Res 1991; 193:59-71. [PMID: 1995302 DOI: 10.1016/0014-4827(91)90538-6] [Citation(s) in RCA: 30] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
We have characterized a new antibody specificity in a panel of sera from dogs developing systemic lupus erythematosus (SLE) or clinically related autoimmune disorders. This antibody stains in a speckled fashion the nucleus of cells of different mammalian origins. The target antigen is a basic (pI 9.2) nuclear polypeptide with an apparent molecular weight of 43 kDa (p43) which is detected in various mammalian cell nuclei. p43, as studied in HeLa cells, appears to be cell cycle-independent. It is released from nuclei by salts (0.5 M NaCl or 0.25 M ammonium sulfate). Upon subfractionation of nuclear components, p43 is found in the fraction containing HnRNPs and is recovered in immunoprecipitates obtained with 4F4 monoclonal antibody to HnRNP C proteins. Immunoelectron microscopy revealed that p43 is concentrated over the dense chromatin periphery and interchromatin granule clusters. Another important feature of p43 is its ability to specifically bind wheat germ agglutinin lectin but not concanavalin A nor Ulex europaeus I, supporting the notion that p43 is a glycoprotein bearing an N-acetyl-glucosamine moiety. Consistent with this result, a radio-active p43 band is specifically immunoprecipitated by canine anti-p43 autoantibodies from HeLa cells metabolically labeled with [14C]glucosamine. Finally, anti-p43 antibodies do not immunoprecipitate SnRNA, indicating that p43 has no apparent association with SnRNPs.
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Affiliation(s)
- M Soulard
- INSERM U-301, Institut de Génétique Moléculaire, Paris, France
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139
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Affiliation(s)
- D D Newmeyer
- La Jolla Cancer Research Foundation, California 92037
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140
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Dabauvalle MC, Loos K, Scheer U. Identification of a soluble precursor complex essential for nuclear pore assembly in vitro. Chromosoma 1990; 100:56-66. [PMID: 2101351 DOI: 10.1007/bf00337603] [Citation(s) in RCA: 84] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
We analysed the soluble form in which the nuclear pore complex protein p68 is stored in Xenopus laevis 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 of nuclear pore complexes from Xenopus oocytes, is located in the pore channel and participates in mediated transport of karyophilic proteins. Using a monoclonal antibody directed against p68 (PI1) we removed this protein from Xenopus egg extract by immunoadsorption. On addition of lambda DNA the immuno-depleted extract supported reconstitution of nuclei which were surrounded by a continuous double-membrane envelope but lacked pore complexes and were unable to import karyophilic proteins such as nucleoplasmin or lamin LIII. Essentially identical results were obtained with extract depleted of WGA-binding proteins. Our finding that both the anti-p68 antibody and WGA efficiently removed components from the extract necessary for pore complex assembly but did not interfere with nuclear membrane formation demonstrates that these processes are independent of each other. Analysis of the immunoprecipitate on silver-stained SDS-polyacrylamide gels indicated that the antibody adsorbed other proteins besides p68, notably two high molecular weight components. By sucrose gradient centrifugation and gel filtration we showed that p68 together with associated protein(s) forms a stable, approximately globular complex with an Mr of 254,000, a Stokes radius of 5.2 nm and a sedimentation coefficient of 11.3 S. Our finding that p68 occurs in the form of larger macromolecular assemblies offers an explanation for the distinctly punctate immunofluorescence pattern observed in the cytoplasm of mitotic cells after staining with antibodies to p68.
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Affiliation(s)
- M C Dabauvalle
- Institute of Zoology I, University of Würzburg, Federal Republic of Germany
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141
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Abstract
Nuclear proteins are actively and posttranslationally transported across the nuclear envelope. This transport is a highly selective process that can be divided into two steps, receptor-binding followed by translocation through the nuclear envelope. Receptor-binding is mediated by nuclear localization signals that have been identified in many nuclear proteins. Translocation is energy-dependent and occurs through the nuclear pore complex.
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Affiliation(s)
- P Wagner
- Department of Biochemistry, University of Basel, Switzerland
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142
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Abstract
The double membrane of the nuclear envelope is a formidable barrier separating the nucleus and cytoplasm of eukaryotic cells. However, movement of specific macromolecules across the nuclear envelope is critical for embryonic development, cell growth and differentiation. Transfer of molecules between the nucleus and cytoplasm occurs through the aqueous channel formed by the nuclear pore complex (NPC). Although small molecules may simply diffuse across the NPC, transport of large proteins and RNA requires specific transport signals and is energy dependent. A family of pore glycoproteins modified by O-linked N-acetylglucosamine moieties are essential for transport through the NPC. Recent evidence suggests that the regulation of nuclear transport may also involve the interaction of RNA and nuclear proteins with specific binding proteins that recognize these transport signals. Are these nuclear pore glycoproteins and signal binding proteins the 'gatekeepers' that control access to the genetic material? Recent evidence obtained from a combination of biochemical and genetic approaches suggests--perhaps.
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Affiliation(s)
- C M Starr
- Laboratory of Biochemistry and Metabolism, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892
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143
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Abstract
Monoclonal antibodies generated against a family of related nuclear pore complex proteins (nucleoporins) from rat liver nuclei cross-react with several proteins in the yeast S. cerevisiae and show punctate nuclear envelope staining similar to the pattern seen in mammalian cells. We have cloned a gene encoding one of these proteins (NUP1) and have confirmed the localization of the NUP1 protein to the pore complex by immunofluorescence, using an epitope-tagged construct to differentiate it from other members of this family. The NUP1 protein is essential for cell viability, and overexpression from the yeast GAL10 promoter prevents further cell growth. The central domain of NUP1 consists of a series of degenerate repeats similar to those found in the nucleoskeletal protein NSP1, a protein that cross-reacts with monoclonal antibodies against NUP1. We propose that the repetitive domain is a feature common to the nucleoporins.
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Affiliation(s)
- L I Davis
- Whitehead Institute for Biomedical Research, Cambridge, Massachusetts
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144
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Glycosylation of nuclear pore protein p62. Reticulocyte lysate catalyzes O-linked N-acetylglucosamine addition in vitro. J Biol Chem 1990. [DOI: 10.1016/s0021-9258(19)39229-4] [Citation(s) in RCA: 65] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
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145
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Haltiwanger RS, Holt GD, Hart GW. Enzymatic addition of O-GlcNAc to nuclear and cytoplasmic proteins. Identification of a uridine diphospho-N-acetylglucosamine:peptide beta-N-acetylglucosaminyltransferase. J Biol Chem 1990. [DOI: 10.1016/s0021-9258(19)39838-2] [Citation(s) in RCA: 248] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
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146
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Finlay DR, Forbes DJ. Reconstitution of biochemically altered nuclear pores: transport can be eliminated and restored. Cell 1990; 60:17-29. [PMID: 2295087 DOI: 10.1016/0092-8674(90)90712-n] [Citation(s) in RCA: 198] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Biochemically altered nuclear pores specifically lacking the N-acetylglucosamine-bearing pore proteins were constructed in a nuclear assembly extract in order to assign function to these proteins. The depleted pores do not bind nuclear signal sequences or actively import nuclear proteins, but they are functional for diffusion. These defects can be fully repaired by assembly with readded Xenopus pore glycoproteins. Strikingly, isolated rat pore glycoproteins also restore transport. Electron microscopy reveals that depleted pores have largely normal morphology. Thus, the pore glycoproteins are not required for assembly of the nuclear envelope, the major structures of the pore, or a pore diffusional channel. Instead, they are essential for active protein import and, unexpectedly, for construction of the part of the pore necessary for signal sequence recognition.
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Affiliation(s)
- D R Finlay
- Department of Biology B-022, University of California, San Diego, La Jolla 92093
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147
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Affiliation(s)
- E A Nigg
- Swiss Institute for Experimental Cancer Research (ISREC), Epalinges
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148
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Benavente R, Dabauvalle MC, Scheer U, Chaly N. Functional role of newly formed pore complexes in postmitotic nuclear reorganization. Chromosoma 1989; 98:233-41. [PMID: 2692995 DOI: 10.1007/bf00327308] [Citation(s) in RCA: 31] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
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 PtK2 cells with WGA or antibody PI1 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 PtK2 cells with blocked nuclear protein uptake completed cytokinesis, their nuclei showed a telophase-like completed cytokinesis, their nuclei showed a telophase-like 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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Affiliation(s)
- R Benavente
- Institute of Zoology I, University of Würzburg, Federal Republic of Germany
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149
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150
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Caillet-Boudin ML, Strecker G, Michalski JC. O-linked GlcNAc in serotype-2 adenovirus fibre. EUROPEAN JOURNAL OF BIOCHEMISTRY 1989; 184:205-11. [PMID: 2776765 DOI: 10.1111/j.1432-1033.1989.tb15008.x] [Citation(s) in RCA: 33] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Serotype-2 adenovirus fibre is shown to possess an O-linked GlcNAc residue and to have affinity for wheat germ agglutinin. The cytoplasmic and nuclear fibres are both glycosylated. Glycosylation seems to take place in the cytoplasm since most of the [14C]GlcN-labelled fibre is found in this compartment, little label being associated with the microsomes. Glycosylation of the fibre was not affected by inhibitors of N- and O-glycosylation. A variation in fibre glycosylation is observed among adenovirus. Among the serotypes tested, only serotype-5 adenovirus (another subgroup C virus) also incorporated [14C]GlcN into its fibre, but did not possess affinity for wheat-germ agglutinin. The GlcNAc is located in the N-terminal two-thirds of the fibre and more probably in the N-terminal one-third. The free or penton-base-associated fibres are similarly glycosylated. These results suggest that glycosylation is not involved in viral adsorption and in assembly with the capsid penton base. Thus, glycosylation might be a characteristic feature of subgroup C viruses.
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Affiliation(s)
- M L Caillet-Boudin
- Unité de Virologie Moléculaire de l'Institut National de la Santé et de la Recherche Medicale, Lille, France
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