Search results for "Nuclear Envelope"
showing 10 items of 26 documents
Diffusion through thin membranes: Modeling across scales
2016
From macroscopic to microscopic scales it is demonstrated that diffusion through membranes can be modeled using specific boundary conditions across them. The membranes are here considered thin in comparison to the overall size of the system. In a macroscopic scale the membrane is introduced as a transmission boundary condition, which enables an effective modeling of systems that involve multiple scales. In a mesoscopic scale, a numerical lattice-Boltzmann scheme with a partial-bounceback condition at the membrane is proposed and analyzed. It is shown that this mesoscopic approach provides a consistent approximation of the transmission boundary condition. Furthermore, analysis of the mesosco…
Unique Organization of the Nuclear Envelope in the Post-natal Quiescent Neural Stem Cells
2017
Summary Neural stem cells (B1 astrocytes; NSCs) in the adult ventricular-subventricular-zone (V-SVZ) originate in the embryo. Surprisingly, recent work has shown that B1 cells remain largely quiescent. They are reactivated postnatally to function as primary progenitors for neurons destined for the olfactory bulb and some corpus callosum oligodendrocytes. The cellular and molecular properties of quiescent B1 cells remain unknown. Here we found that a subpopulation of B1 cells has a unique nuclear envelope invagination specialization similar to envelope-limited chromatin sheets (ELCS), reported in certain lymphocytes and some cancer cells. Using molecular markers, [3H]thymidine birth-dating, …
Protoparvovirus Knocking at the Nuclear Door
2017
Protoparvoviruses target the nucleus due to their dependence on the cellular reproduction machinery during the replication and expression of their single-stranded DNA genome. In recent years, our understanding of the multistep process of the capsid nuclear import has improved, and led to the discovery of unique viral nuclear entry strategies. Preceded by endosomal transport, endosomal escape and microtubule-mediated movement to the vicinity of the nuclear envelope, the protoparvoviruses interact with the nuclear pore complexes. The capsids are transported actively across the nuclear pore complexes using nuclear import receptors. The nuclear import is sometimes accompanied by structural chan…
YAP/TAZ activity in stromal cells prevents ageing by controlling cGAS-STING
2022
Ageing is intimately connected to the induction of cell senescence(1,2), but why this is so remains poorly understood. A key challenge isthe identification of pathways that normally suppress senescence, are lost during ageing and are functionally relevant to oppose ageing(3). Here we connected the structural and functional decline of ageing tissues to attenuated function of the master effectors of cellular mechanosignalling YAP and TAZ. YAP/TAZ activity declines during physiological ageing in stromal cells, and mimicking such decline through genetic inactivation of YAP/TAZ in these cells leads to accelerated ageing. Conversely, sustaining YAP function rejuvenates old cells and opposes the e…
Cargo transport through the nuclear pore complex at a glance.
2021
ABSTRACT Bidirectional transport of macromolecules across the nuclear envelope is a hallmark of eukaryotic cells, in which the genetic material is compartmentalized inside the nucleus. The nuclear pore complex (NPC) is the major gateway to the nucleus and it regulates nucleocytoplasmic transport, which is key to processes including transcriptional regulation and cell cycle control. Accordingly, components of the nuclear transport machinery are often found to be dysregulated or hijacked in diseases. In this Cell Science at a Glance article and accompanying poster, we provide an overview of our current understanding of cargo transport through the NPC, from the basic transport signals and mach…
Alteration of nuclear (2'-5')oligoriboadenylate synthetase and nuclease activities preceding replication of human immunodeficiency virus in H9 cells.
1988
After infection of the respective target cells with the human immunodeficiency virus (HIV-1) viral progeny is produced only after a short temporary delay of some days, depending on cell type. After this period of time a sudden onset of HIV-1 protein synthesis with a dramatic increase in virus release occurs. (2'-5')Oligoriboadenylates [(2'-5')A], capable to activate a latent ribonuclease (RNase L) degrading both mRNA and rRNA, are known mediators involved in the early response of cells to virus infection. Here we show that the (2'-5')A-synthesizing (2'-5')A synthetase, which is inducible by interferon and activated by double-stranded RNA, as well as a (2'-5')A nuclease (2',3'-exoribonucleas…
The Complex Regulatory Role of Cytomegalovirus Nuclear Egress Protein pUL50 in the Production of Infectious Virus
2021
The regulation of the nucleocytoplasmic release of herpesviral capsids is defined by the process of nuclear egress. Due to their large size, nuclear capsids are unable to traverse via nuclear pores, so that herpesviruses evolved to develop a vesicular transport pathway mediating their transition through both leaflets of the nuclear membrane. This process involves regulatory proteins, which support the local distortion of the nuclear envelope. For human cytomegalovirus (HCMV), the nuclear egress complex (NEC) is determined by the pUL50-pUL53 core that initiates multicomponent assembly with NEC-associated proteins and capsids. Hereby, pUL50 serves as a multi-interacting determinant that recru…
Studies on protein kinases involved in regulation of nucleocytoplasmic mRNA transport
1988
The rate of energy-dependent nucleoside triphosphatase (NTPase)-mediated nucleocytoplasmic translocation of poly(A)-containing mRNA [poly(A)+mRNA] across the nuclear envelope is thought to be regulated by poly(A)-sensitive phosphorylation and dephosphorylation of nuclear-envelope protein. Studying the phosphorylation-related inhibition of the NTPase, we found that phosphorylation of one polypeptide of rat liver envelopes by endogenous NI- and NII-like protein kinase was particularly sensitive to poly(A). This polypeptide (106 kDa) was also phosphorylated by nuclear-envelope-bound Ca2+-activated and phospholipid-dependent protein kinase (protein kinase C). Activation of kinase C by tumour-pr…
Modulation of the nuclear-envelope nucleoside triphosphatase by poly(A)-rich mRNA and by microtubule protein.
1982
Nuclear envelopes contain a nucleoside triphosphatase which is thought to be involved in the supply of energy for nucleo-cytoplasmic RNA transport. This enzyme is stimulated most efficiently by poly(A) and to a lesser extent by poly(G) and poly(dT). Half-maximal stimulation of the enzyme from rat liver nuclei, which was associated with the poly(A)-specific endoribonuclease IV and was free from poly(A) polymerase and endoribonuclease V activity, was determined to occur at a concentration of 1.1 × 106 poly(A) molecules/nuclear ghost. Double-reciprocal plot analyses revealed a 2.8-fold stimulation of the enzyme by poly(A). Poly(A) in the hybrid form had no influence on the activity of the nucl…
Differential effect of insulin and epidermal growth factor on the mRNA translocation system and transport of specific poly(A+) mRNA and poly(A-) mRNA…
1990
The efficiency of efflux of rapidly labeled poly(A)-containing mRNA from isolated rat liver nuclei was found to be modulated by insulin and epidermal growth factor (EGF) in a biphasic but opposite way. At physiological concentrations (10 pM insulin and 1 pM EGF), maximal stimulation of the transport rate by insulin (to 137%) and maximal inhibition by EGF (to 69%) were obtained; at higher concentrations (greater than 100 pM and greater than 10 pM, respectively), the amount of poly(A)-containing mRNA released into the postnuclear supernatant was nearly identical with the level found in untreated nuclei (= 100%). Using mRNA entrapped into closed nuclear envelope (NE) vesicles as a model system…