Pre-assembled Nuclear Pores Insert into the Nuclear Envelope during Early Development (original) (raw)
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Nuclear Pores Assemble from Nucleoporin Condensates During Oogenesis
Cell, 2019
The molecular events that direct nuclear pore complex (NPC) assembly toward nuclear envelopes have been conceptualized in two pathways that occur during mitosis or interphase, respectively. In gametes and embryonic cells, NPCs also occur within stacked cytoplasmic membrane sheets, termed annulate lamellae (AL), which serve as NPC storage for early development. The mechanism of NPC biogenesis at cytoplasmic membranes remains unknown. Here, we show that during Drosophila oogenesis, Nucleoporins condense into different precursor granules that interact and progress into NPCs. Nup358 is a key player that condenses into NPC assembly platforms while its mRNA localizes to their surface in a translation-dependent manner. In concert, Microtubule-dependent transport, the small GTPase Ran and nuclear transport receptors regulate NPC biogenesis in oocytes. We delineate a non-canonical NPC assembly mechanism that relies on Nucleoporin condensates and occurs away from the nucleus under conditions of cell cycle arrest.
The nuclear pore complex: nucleocytoplasmic transport and beyond
Nature Reviews Molecular Cell Biology, 2003
In interphase eukaryotic cells, the double-membraned nuclear envelope (NE) spatially separates the cytoplasm from the cell nucleus. Embedded in the NE are nuclear pore complexes (NPCs), which allow the diffusion of ions and small molecules across the NE and facilitate the receptor-mediated bidirectional transport of proteins, RNAs and ribonucleoprotein (RNP) particles 1,2,3 .A consensus model of the three-dimensional (3D) NPC architecture has evolved from extensive electron-microscopy (EM) studies, which have mainly involved nuclei from Xenopus laevis oocytes. The vertebrate NPC has a tripartite architecture -it has a central framework that is 'decorated' by the cytoplasmic filaments and a nuclear basket . In the plane of the NE, the NPC has an eightfold symmetry , and its total mass has been estimated to be 90-120 MDa (REFS 1,. The central framework of the NPC (that is, the portion of the NPC that resides in the NE; also known as the spoke complex) is composed of eight multidomain spokes, and each spoke consists of two roughly identical halves that are placed back-to-back in the midplane of the NE. This membrane-spanning domain of the NPC is continuous with the cytoplasmic and nuclear ring moieties 7 . From the cytoplasmic ring moiety, eight, short, kinky filaments emanate towards the cytoplasm, whereas the nuclear ring moiety is the anchor for eight filaments that are attached to a distal ring and that form the nuclear basket (also known as the 'fish trap').
Journal of Cell Biology, 1984
Annulate lamellae are cytoplasmic organelles composed of stacked sheets of membrane containing pores that are structurally indistinguishable from nuclear pores. The functions of annulate lamellae are not well understood. Although they may be found in virtually any eucaryotic cell, they occur most commonly in transformed and embryonic tissues. In Drosophila, annulate lamellae are found in the syncytial blastoderm embryo as it is cleaved to form the cellular blastoderm. The cytological events of the cellularization process are well documented, and may be used as temporal landmarks when studying changes in annulate lamellae. By using morphometric techniques to analyze electron micrographs of embryos, we are able to calculate the number of pores per nucleus in nuclear envelopes and annulate lamellae during progressive stages of cellularization. We find that annulate lamellae pores remain at a low level while nuclear envelopes are expanding and acquiring pores in early interphase. Once n...
The cellular environment shapes the nuclear pore complex architecture
Nature, 2021
Nuclear pore complexes (NPCs) create large conduits for cargo transport between the nucleus and cytoplasm across the nuclear envelope (NE)1–3. These multi-megadalton structures are composed of about thirty different nucleoporins that are distributed in three main substructures (the inner, cytoplasmic and nucleoplasmic rings) around the central transport channel4–6. Here we use cryo-electron tomography on DLD-1 cells that were prepared using cryo-focused-ion-beam milling to generate a structural model for the human NPC in its native environment. We show that—compared with previous human NPC models obtained from purified NEs—the inner ring in our model is substantially wider; the volume of the central channel is increased by 75% and the nucleoplasmic and cytoplasmic rings are reorganized. Moreover, the NPC membrane exhibits asymmetry around the inner-ring complex. Using targeted degradation of Nup96, a scaffold nucleoporin of the cytoplasmic and nucleoplasmic rings, we observe the int...
Regulation and coordination of nuclear envelope and nuclear pore complex assembly
Nucleus (Austin, Tex.)
In metazoans with "open" mitosis, cells undergo structural changes involving the complete disassembly of the nuclear envelope (NE). In post-mitosis, the dividing cell faces the difficulty to reassemble NE structures in a highly regulated fashion around separated chromosomes. The de novo formation of nuclear pore complexes (NPCs), which are gateways between the cytoplasm and nucleoplasm across the nuclear membrane, is an archetype of macromolecular assembly and is therefore of special interest. The reformation of a functional NE further involves the reassembly and organization of other NE components, the nuclear membrane and NE proteins, around chromosomes in late mitosis. Here, we discuss the function of NE components, such as lamins and INM proteins, in NE reformation and highlight recent results on coordination of NPC and NE assembly.
The nuclear pore complex: a jack of all trades?
Trends in Biochemical Sciences, 2004
The nuclear pore complex (NPC) is the only gateway between the cell nucleus and the cytoplasm, and it mediates all movement between these two compartments. The past few years have witnessed much progress on its structure and molecular architecture, its interaction with soluble transport receptors, and how nucleocytoplasmic transport is regulated by the small GTPase Ran. However, the exact molecular mechanisms underlying nucleocytoplasmic transport and in particular cargo translocation through the NPC are understood only poorly. Recent findings on the interaction between the NPC and transport factors might provide insights into how efficient NPC translocation is accomplished. Moreover, in addition to mediating nucleocytoplasmic transport, the NPC seems to be involved, either directly or indirectly, in many other cellular processes such as chromosome segregation, gene expression, the secretory pathway and apoptosis.
Reconstitution of nuclear pore assembly and function
Seminars in Cell & Developmental Biology, 1996
Nuclear pore complexes are the vital communication links that permit the regulated movement of macromolecules between the cytoplasm and nucleus of a cell. As with many other complex cellular events, much of our understanding about pore dynamics and function comes from studying systems that faithfully reproduce these processes in vitro. Two systems have provided the bulk of our knowledge. The first system reconstitutes nuclear import into permeabilized cultured cells. Import is dependent on exogenously added cytosol, and fractionation of this cytosol has led to the identification and characterization of most of the nuclear transport factors. The second system uses a nuclear reconstitution system derived from Xenopus eggs to study transport and to assemble nuclear pores from their component parts. This system has allowed the characterization of both individual pore components and distinct steps in the pore assembly pathway.