![]() The images show immunofluorescent stainings of the protein LBR in HEK 293, U2OS and RH-30 cells.įigure 4. Examples of the morphology of nuclear membrane in different cell lines, where the morphology is relatively consistent. The membrane is however not perfectly smooth and the membranous cavities can appear as small circles or dots inside the nucleus, not to be confused with nuclear bodies.įigure 3. When imaging an intersection of the cell, the nuclear membrane is visible as a thin circle along the outer rim of the nucleus, which is consistent between cell lines (Figure 3). Each nuclear pore complex consists of 100-200 proteins that form a characteristic eight-fold ring symmetry ( Paine PL et al. The membranes are connected to each other by large protein complexes, known as nuclear pore complexes, forming a large number of channels that allows for transport in and out of the nucleus. The space between the inner and the outer membrane is called the perinuclear space. Translocated promoter region, nuclear basket protein Highly expressed single localized nuclear membrane proteins across different cell lines. Selection of proteins suitable as markers for the nuclear membrane. A list of highly expressed nuclear membrane proteins, including lamins, are summarized in Table 2. A selection of proteins suitable as markers for the nuclear lamina and the nuclear membrane can be found in Table 1. During the mitotic phase of cell division, B-type lamins will remain associated to membranes, whereas A-type lamins are solubilized and dispersed ( Gruenbaum Y et al. Lamins are classified as A- or B-type lamins, and exhibit different biochemical and functional properties in terms of isoelectric points and behavior during mitosis. It has been suggested that lamins may also participate in DNA repair, as well as regulation of DNA replication and transcription ( Dechat T et al. The nuclear lamina provides structural support and acts as an anchoring point for chromatin, thus playing an important role in nuclear organization. The outermost membrane is contiguous with the endoplasmic reticulum (ER), while the innermost membrane is lined by a fibrillar network consisting of nuclear intermediate filament proteins, known as nuclear lamins. The nuclear membrane, also known as the nuclear envelope, consists of two lipid bilayers. SUN2 is known to be part of the LINC protein complexes that enables connection of the cytoskeleton to the nuclear membrane (detected in A-431 cells). LMNB1 is a part of the nuclear lamina, and is a type of intermediate filament protein (detected in MCF7 cells). TPR is part of the nuclear pore complex required in nuclear trafficking, and is specifically involved in nuclear export of mRNAs (detected in A-431 cells). Examples of proteins localized to the nuclear membrane. About 86% (n= 242) of the nuclear membrane proteins localize to other cellular compartments in addition to the nuclear membrane, with 28% (n= 78) also localizing to other substructures within the nuclear meta compartment.įigure 1. A Gene Ontology (GO)-based functional enrichment analysis of the nuclear membrane proteins show enrichment of terms for biological processes mainly related to structural organization of the nucleus and nucleocytoplasmic transport. In the subcellular section, 280 genes (1% of all protein-coding human genes) have been shown to encode proteins that localize to the nuclear membrane (Figure 2). Example images of proteins localized to the nuclear membrane can be seen in Figure 1. The nuclear membrane consists of two lipid bilayers enclosing the nucleus and physically isolating it from the rest of the cell, which enables important molecular processes to occur in the nucleus without interference from the cytoplasm. 2007).Ever since Robert Brown's discovery of the nucleus in 1833 it has been known that the nucleus is surrounded by a membranous structure. 2005) is considered to be one of the key steps in the detachment of the nuclear envelope from chromatin (Bengtsson and Wilson 2006, Nichols et al. 2001, Mansharamani and Wilson 2005, Brachner et al. VRK1 (and possibly VRK2) mediated phosphorylation of BANF1 (BAF), a protein that simultaneously interacts with DNA, LEM-domain inner nuclear membrane proteins, and lamins (Zheng et al. In mitotic prophase, chromatin detaches from the nuclear envelope, and this contributes to the nuclear envelope breakdown. For a recent review, please refer to Guttinger et al. NEBD allows mitotic spindle microtubules to access condensed chromosomes at kinetochores and enables nuclear division and segregation of genetic material to two daughter cells. The nuclear envelope breakdown (NEBD) happens in late prophase of mitosis and involves disassembly of the nuclear pore complex, depolymerization of the nuclear lamina, and clearance of nuclear envelope from chromatin.
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