Your browser doesn't support javascript.
loading
Show: 20 | 50 | 100
Results 1 - 8 de 8
Filter
Add more filters










Database
Language
Publication year range
1.
Article in English | MEDLINE | ID: mdl-21209392

ABSTRACT

Nuclear lamins were originally described as the main constituents of the nuclear lamina, a filamentous meshwork closely associated with the inner nuclear membrane. However, within recent years, it has become increasingly evident that a fraction of lamins also resides throughout the nuclear interior. As intermediate-filament-type proteins, lamins have been suggested to fulfill mainly structural functions such as providing shape and mechanical stability to the nucleus. But recent findings show that both peripheral and nucleoplasmic lamins also have important roles in essential cellular processes such as transcription, DNA replication, cell cycle progression, and chromatin organization. Furthermore, more than 300 mutations in the gene encoding A-type lamins have been associated with several human diseases now generally termed laminopathies and comprising muscular dystrophies, lipodystrophies, cardiomyopathies, and premature aging diseases. This review focuses on the lamina-independent pool of lamins in the nuclear interior, which surprisingly has not been studied in much detail so far. We discuss the properties and regulation of nucleoplasmic lamins during the cell cycle, their interaction partners, and their potential involvement in cellular processes and the development of laminopathies.


Subject(s)
Lamins/metabolism , Nuclear Lamina/metabolism , Animals , Disease , Humans , Lamins/chemistry
2.
J Neural Transm (Vienna) ; 111(9): 1155-65, 2004 Sep.
Article in English | MEDLINE | ID: mdl-15338331

ABSTRACT

The Vienna Transdanube Aging (VITA) study searches for early markers of Alzheimer's disease (AD) by examining the mental status in a community-based cohort of 606, 75-years old volunteers that are then related to various clinical and genetic analyses. To determine whether mutations in mtDNA are involved in expression of AD, the mtDNA of 79 "control" participants is screened for alterations by sequencing of "hot-spot-regions". This study on mtDNA mutations has eliminated the influence of aging on the occurrence of mtDNA alterations by sequencing samples from persons at the age of exactly 75 years. Thus, our cohort reveals a snap-shot of mitochondrial sequences of elderly persons. So far, a high percentage (56%) of persons with known or unknown mutations in the fragments analyzed were found. These data will be compared in due time to a cohort of participants with proven late-onset AD.


Subject(s)
Alzheimer Disease/genetics , DNA, Mitochondrial/genetics , Genetic Predisposition to Disease/genetics , Aged , Alzheimer Disease/epidemiology , Amino Acid Substitution/genetics , Austria/epidemiology , Cohort Studies , Cross-Sectional Studies , DNA Mutational Analysis , Female , Genetic Testing , Genotype , Haplotypes/genetics , Humans , Longitudinal Studies , Male , Mutation/genetics , Polymorphism, Single Nucleotide/genetics , Predictive Value of Tests , Risk
3.
Cell Mol Life Sci ; 58(12-13): 1758-65, 2001 Nov.
Article in English | MEDLINE | ID: mdl-11767745

ABSTRACT

The peripheral nuclear lamina is located near the nuclear inner membrane and consists of lamin filaments and integral membrane proteins, including the lamin B receptor and various isoforms of lamina-associated polypeptides (LAP) 1 and 2. Several nuclear membrane proteins also interact with chromatin proteins BAF and Hp1. Lamins in the nuclear interior associate with at least one soluble (non-membrane-bound) LAP2 isoform named LAP2alpha. The internal lamins, together with Tpr-based filaments that connect to nuclear pore complexes, are proposed to be major structural elements of the internal nuclear matrix. We describe the structural links between the peripheral lamina and the internal nuclear matrix that are thought to be mediated by LAP2 family members, filament protein Tpr and nucleoporin Nup153. These findings are discussed in relation to human diseases that arise from mutations in nuclear lamina proteins.


Subject(s)
Nuclear Envelope/metabolism , Nuclear Matrix/metabolism , Active Transport, Cell Nucleus/physiology , Animals , Cell Cycle/physiology , Chromatin/metabolism , HeLa Cells , Humans , Lamin Type B , Lamins , Microscopy, Fluorescence , Models, Biological , Nuclear Envelope/chemistry , Nuclear Matrix/chemistry , Nuclear Pore Complex Proteins/metabolism , Nuclear Proteins/metabolism , Protein Isoforms , Proto-Oncogene Proteins/metabolism
4.
J Cell Sci ; 113 Pt 19: 3473-84, 2000 Oct.
Article in English | MEDLINE | ID: mdl-10984438

ABSTRACT

The nucleoskeletal protein lamina-associated polypeptide 2(&agr;) (LAP2*) contains a large, unique C terminus and differs significantly from its alternatively spliced, mostly membrane-integrated isoforms, such as LAP2beta. Unlike lamin B-binding LAP2beta, LAP2alpha was found by confocal immunofluorescence microscopy to colocalize preferentially with A-type lamins in the newly formed nuclei assembled after mitosis. While only a subfraction of lamins A and C (lamin A/C) was associated with the predominantly nuclear LAP2alpha in telophase, the majority of lamin A/C colocalized with LAP2alpha in G(1)-phase nuclei. Furthermore, selective disruption of A-type lamin structures by overexpression of lamin mutants in HeLa cells caused a redistribution of LAP2alpha. Coimmunoprecipitation experiments revealed that a fraction of lamin A/C formed a stable, SDS-resistant complex with LAP2alpha in interphase cells and in postmetaphase cell extracts. Blot overlay binding studies revealed a direct binding of LAP2alpha to exclusively A-type lamins and located the interaction domains to the C-terminal 78 amino acids of LAP2alpha and to residues 319-566 in lamin A/C, which include the C terminus of the rod and the entire tail common to lamin A/C. These findings suggest that LAP2alpha and A-type lamins cooperate in the organization of internal nuclear structures.


Subject(s)
Cell Nucleus/metabolism , DNA-Binding Proteins , Membrane Proteins/metabolism , Nuclear Proteins/metabolism , Amino Acid Motifs , Animals , Blotting, Western , Cell Line , Cell Nucleus/chemistry , DNA/metabolism , Fluorescent Dyes , HeLa Cells , Hepatocytes/cytology , Humans , Interphase , Lamin Type A , Lamin Type B , Lamins , Membrane Proteins/genetics , Microscopy, Confocal , Microscopy, Fluorescence , Mitosis , Nocodazole/pharmacology , Nuclear Proteins/genetics , Nuclear Proteins/immunology , Peptide Fragments/metabolism , Precipitin Tests , Protein Binding , Rats , Recombinant Proteins/genetics , Recombinant Proteins/metabolism
5.
J Struct Biol ; 129(2-3): 335-45, 2000 Apr.
Article in English | MEDLINE | ID: mdl-10806084

ABSTRACT

The lamina-associated polypeptide (LAP) 2 family comprises up to six alternatively spliced proteins in mammalian cells and three isoforms in Xenopus. LAP2beta is a type II integral protein of the inner nuclear membrane, which binds to lamin B and the chromosomal protein BAF, and may link the nuclear membrane to the underlying lamina and provide docking sites for chromatin. LAP2alpha shares only the N-terminus with the other isoforms and contains a unique C-terminus. It is a nonmembrane protein associated with the nucleoskeleton and may help to organize higher order chromatin structure by interacting with A-lamins and chromosomes. Recent studies using mutant proteins have just begun to unravel functions of LAP2 isoforms during postmitotic nuclear reassembly. LAP2alpha associates with chromosomes via an alpha-specific domain at early stages of assembly, possibly providing a structural framework for chromosome reorganization. The subsequent interaction of both LAP2alpha and LAP2beta with the chromosomal BAF may stabilize chromatin structure and target membranes to the chromosomes. At later stages LAP2 may regulate the assembly of lamins. LAP2 isoforms have been found to share a homologous approximately 40 amino acid long region, the LEM domain, with nuclear membrane proteins MAN1 and emerin, which has been implicated in Emery-Dreifuss muscular dystrophy.


Subject(s)
Cell Cycle/physiology , Cell Nucleus/physiology , Cell Nucleus/ultrastructure , DNA-Binding Proteins , Membrane Proteins/physiology , Nuclear Proteins/physiology , Animals , Chromosomes/physiology , Chromosomes/ultrastructure , Humans , Mitosis , Nuclear Envelope/physiology , Protein Isoforms/physiology
6.
J Cell Biochem ; 76(4): 559-66, 2000 Jan.
Article in English | MEDLINE | ID: mdl-10653975

ABSTRACT

A monoclonal antibody raised against nuclear matrix proteins detected a protein of basic pI in human nuclear matrix protein samples of various cellular origin. The ubiquitously occurring (common) nuclear matrix protein was identified as splicing factor PSF (PTB associated splicing factor). The interaction between the splicing factors PSF and PTB/hnRNP I was confirmed by co-immunoprecipitation from nuclear salt extracts. However, the nuclear localization of PSF and PTB and their distribution in subnuclear fractions differed markedly. Isolated nuclear matrices contained the bulk of PSF, but only minor amounts of PTB. In confocal microscopy both proteins appeared in speckles, the majority of which did not co-localize. Removing a large fraction of the soluble PTB structures by salt extraction revealed some colocalization of the more stable PTB fraction with PSF. These PTB/PSF complexes as well as the observed PSF-PTB interaction may reflect the previously reported presence of PTB and PSF in spliceosomal complexes during RNA processing. The present data, however, point to different cellular distribution and nuclear matrix association of the majority of PSF and PTB.


Subject(s)
DNA-Binding Proteins/metabolism , Nuclear Matrix/metabolism , Nuclear Proteins/metabolism , RNA Splicing , RNA-Binding Proteins/metabolism , Antibodies, Monoclonal/immunology , Antigens, Nuclear , Electrophoresis, Gel, Two-Dimensional , Fluorescent Antibody Technique , HL-60 Cells , HeLa Cells , Humans , Microscopy, Confocal , PTB-Associated Splicing Factor , Polypyrimidine Tract-Binding Protein , Precipitin Tests
7.
EMBO J ; 18(22): 6370-84, 1999 Nov 15.
Article in English | MEDLINE | ID: mdl-10562549

ABSTRACT

Lamina-associated polypeptide 2alpha (LAP2alpha) is a non-membrane-bound isoform of the LAP2 family implicated in nuclear structure organization. We show that during postmitotic nuclear assembly LAP2alpha associates with chromosomes prior to accumulation of the membrane-bound isoform LAP2beta, although both proteins contain the same putative chromatin interaction domains located in their common N-terminal regions. By transient and stable expression of various N- and C-terminal LAP2alpha deletion mutants in HeLa cells, we identified an approximately 350-amino-acid-long region in the C-terminal alpha-specific domain of the protein that is required for retention of LAP2alpha in interphase nuclei and for association with mitotic chromosomes, while the N-terminal domain seemed to be dispensable for these interactions. In vitro chromosome binding studies using recombinant LAP2alpha mutants revealed that this LAP2alpha-specific 'nuclear targeting domain' was essential and sufficient for association with chromosomes. These data suggested a functional diversity of chromosome binding properties of LAP2 isoforms.


Subject(s)
Cell Cycle/physiology , Cell Nucleus/metabolism , Chromosomes/metabolism , DNA-Binding Proteins , Membrane Proteins/chemistry , Membrane Proteins/metabolism , Nuclear Proteins/chemistry , Nuclear Proteins/metabolism , Animals , Binding Sites , CHO Cells , Cell Line , Cricetinae , HeLa Cells , Humans , Interphase , Membrane Proteins/genetics , Metaphase , Mitosis , Mutagenesis , Nuclear Proteins/genetics , Protein Isoforms/chemistry , Protein Isoforms/genetics , Protein Isoforms/metabolism , Rats , Recombinant Proteins/chemistry , Recombinant Proteins/metabolism , Sequence Deletion , Transfection
8.
EMBO J ; 17(16): 4887-902, 1998 Aug 17.
Article in English | MEDLINE | ID: mdl-9707448

ABSTRACT

Lamina-associated polypeptide (LAP) 2 of the inner nuclear membrane (now LAP2beta) and LAP2alpha are related proteins produced by alternative splicing, and contain a common 187 amino acid N-terminal domain. We show here that, unlike LAP2beta, LAP2alpha behaved like a nuclear non-membrane protein in subcellular fractionation studies and was localized throughout the nuclear interior in interphase cells. It co-fractionated with LAP2beta in nuclear lamina/matrix-enriched fractions upon extraction of nuclei with detergent, salt and nucleases. During metaphase LAP2alpha dissociated from chromosomes and became concentrated around the spindle poles. Furthermore, LAP2alpha was mitotically phosphorylated, and phosphorylation correlated with increased LAP2alpha solubility upon extraction of cells in physiological buffers. LAP2alpha relocated to distinct sites around chromosomes at early stages of nuclear reassembly and intermediarily co-localized with peripheral lamin B and intranuclear lamin A structures at telophase. During in vitro nuclear assembly LAP2alpha was dephosphorylated and assembled into insoluble chromatin-associated structures, and recombinant LAP2alpha was found to interact with chromosomes in vitro. Some LAP2alpha may also associate with membranes prior to chromatin attachment. Altogether the data suggest a role of LAP2alpha in post-mitotic nuclear assembly and in the dynamic structural organization of the nucleus.


Subject(s)
Cell Nucleus/metabolism , DNA-Binding Proteins , Interphase , Membrane Proteins/metabolism , Nuclear Proteins/metabolism , Animals , CHO Cells , Cell Nucleus/ultrastructure , Cricetinae , Detergents , HeLa Cells , Humans , Microscopy, Immunoelectron , Mitosis , Phosphorylation , Salts
SELECTION OF CITATIONS
SEARCH DETAIL
...