Migration, and the organization of syncitia ( Fridkin et al. These ONM proteins are implicated in nuclear positioning that is essential for processes such as cell polarization, pronuclear With the actin cytoskeleton through their amino-terminal actin-binding domain (ABD) ( Wilhelmsen et al. Two other related ONM proteins, nuclear envelope spectrin repeat (nesprin)-1 and -2, have been shown to directly interact Of the NE ( Starr and Han 2003 Wilhelmsen et al. This diverse group of integral membrane proteins shares a small KASH (Klarsicht, ANC-1, Syne Homolgy) domain, which hasīeen shown to interact with Sad1p/UNC-84 (SUN)-domain proteins of the inner nuclear membrane within the periplasmic space Proteomic approaches have identified ∼60 putative transmembrane proteins (NETs), most of which remain uncharacterized.Ī third class of NE proteins specifically resides in the ONM ( Fig. Nurim is a multi-pass membrane protein with unknownįunction. SUN proteins (SUN 1 and 2) interact with nesprins in the ONM, thereby forming so-called LINC complexes thatĮstablish connections to actin and intermediate filaments in the cytoplasm. Protein 2, emerin, MAN1)-domain family (pink) bind to lamins and interact with chromatin through barrier-to-autointegrationįactor (BAF). Lamins and chromatin-associated heterochromatin protein 1 (HP1) in conjunction with core histones. The lamin B receptor (LBR) interacts both with B-type ONM proteins provide a connection from the nucleus to the cytoskeleton. INM proteins link the NE to chromatin and the lamina. The nuclear lamina interacts with NE proteins and chromatin. Inner and outer nuclear membranes (INM and ONM, respectively) are separated by the ER lumen or perinuclear Sparked considerable interest in NE biology over the last decade ( Vlcek and Foisner 2007 Worman and Bonne 2007 Neilan 2009). Importantly, improper localization and function of INM proteins have been linked to numerous human diseases, which has 2006 Heessen and Fornerod 2007 Reddy et al. Organization, gene expression, and DNA metabolism ( Mattout et al. It is becoming increasingly clear that INM proteins play vital and diverse roles in nuclear function such as chromatin Although most of these >60 integral membrane proteins (also referred to as NE transmembrane proteins or NETs ) remain largely uncharacterized, interaction with lamins (see later) and chromatin have been shown for some of them, suchĪs lamin B receptor (LBR), lamina-associated polypeptide (LAP) 1, LAP2, emerin, and MAN1 ( Akhtar and Gasser 2007 Dorner et al. A second group of NE proteins, specifically localizes to the INM ( Fig. Attached to this scaffold are peripheral Nups, many of which contain phenylalanine-glycine (FG) rich repeats that establishĪ permeability barrier and also mediate active, receptor-dependent transport across the NE ( Peters 2009). This core includes the Nup107/160 complex (Nup84 complex in yeast) and the Nup205 complex (yeast Nup170), which togetherĬonstitute ∼50% of the entire NPC ( Fig. 2009), which is thought to stabilize the highly curved and energetically unfavorable pore membrane ( Alber et al. A subset of Nups is stably embedded in the NE, forming a scaffold structure or NPC core ( Rabut et al.

NPCs are aqueous channels that show eightfold rotational symmetry with an outer diameter of ∼100 nm and a central transportĬhannel measuring 40 nm in diameter, through which bidirectional exchange of proteins, RNA, and ribonucleoprotein complexesīetween the nucleoplasm and cytoplasm occurs ( Beck et al. (NPCs) ( Tran and Wente 2006 D'Angelo and Hetzer 2008).

The first group consists of ∼30 different polypeptides, called nucleoporins or Nups, which form the ∼40–70 MD nuclear pore complexes Despite the lipid continuity between the NE and the ER, both ONM and INM are comprised of diverse groups of proteins thatĪre typically not enriched in the ER ( Hetzer et al. The endoplasmic reticulum (ER) ( Watson 1955). Early electron microscopy (EM) images revealed that the inner (INM) and outer nuclear membranes (ONM) are continuous with The NE, a hallmark of eukaryotic cells, is a highly organized double membrane that encloses the nuclear genome ( Kite 1913). Understanding of the dynamic remodeling of the NE during the cell cycle.

Generating the need to re-establish the nuclear compartment at the end of each cell division. To allow access of the mitotic spindle to chromatin, the nucleus of metazoans must completely disassemble during mitosis, It contains a large number of different proteins that have been implicated in chromatin organization and gene regulation.Īlthough the nuclear membrane enables complex levels of gene expression, it also poses a challenge when it comes to cell division. The nuclear envelope (NE) is a highly regulated membrane barrier that separates the nucleus from the cytoplasm in eukaryoticĬells.

Nuclear envelope fragments meaning