scholarly journals Nuclear Import of Adenovirus DNA Involves Direct Interaction of Hexon with an N-Terminal Domain of the Nucleoporin Nup214

2014 ◽  
Vol 89 (3) ◽  
pp. 1719-1730 ◽  
Author(s):  
Aurélia Cassany ◽  
Jessica Ragues ◽  
Tinglu Guan ◽  
Dominique Bégu ◽  
Harald Wodrich ◽  
...  
Keyword(s):  
Amino Acid ◽  
Binding Site ◽  
Nuclear Import ◽  
Viral Genome ◽  
Molecular Basis ◽  
Nuclear Pore ◽  
Viral Dna ◽  
Terminal Domain ◽  
Cytoplasmic Face ◽  
The Impact

ABSTRACTIn this study, we characterized the molecular basis for binding of adenovirus (AdV) to the cytoplasmic face of the nuclear pore complex (NPC), a key step during delivery of the viral genome into the nucleus. We used RNA interference (RNAi) to deplete cells of either Nup214 or Nup358, the two major Phe-Gly (FG) repeat nucleoporins localized on the cytoplasmic side of the NPC, and evaluated the impact on hexon binding and AdV infection. The accumulation of purified hexon trimers or partially disassembled AdV at the nuclear envelope (NE) was observed in digitonin-permeabilized cells in the absence of cytosolic factors. Bothin vitrohexon binding andin vivonuclear import of the AdV genome were strongly reduced in Nup214-depleted cells but still occurred in Nup358-depleted cells, suggesting that Nup214 is a major binding site of AdV during infection. The expression of an NPC-targeted N-terminal domain of Nup214 in Nup214-depleted cells restored the binding of hexon at the NE and the nuclear import of protein VII (pVII), indicating that this region is sufficient to allow AdV binding. We further narrowed the binding site to a 137-amino-acid segment in the N-terminal domain of Nup214. Together, our results have identified a specific region within the N terminus of Nup214 that acts as a direct NPC binding site for AdV.IMPORTANCEAdVs, which have the largest genome of nonenveloped DNA viruses, are being extensively explored for use in gene therapy, especially in alternative treatments for cancers that are refractory to traditional therapies. In this study, we characterized the molecular basis for binding of AdV to the cytoplasmic face of the NPC, a key step for delivery of the viral genome into the nucleus. Our data indicate that a 137-amino-acid region of the nucleoporin Nup214 is a binding site for the major AdV capsid protein, hexon, and that this interaction is required for viral DNA import. These findings provide additional insight on how AdV exploits the nuclear transport machinery for infection. The results could promote the development of new strategies for gene transfer and enhance understanding of the nuclear import of other viral DNA genomes, such as those of papillomavirus or hepatitis B virus that induce specific cancers.

scholarly journals Histone H3 Lysine 4 Methylation Marks Postreplicative Human Cytomegalovirus Chromatin

2012 ◽  
Vol 86 (18) ◽  
pp. 9817-9827 ◽  
Author(s):  
Alexandra Nitzsche ◽  
Charlotte Steinhäußer ◽  
Katrin Mücke ◽  
Christina Paulus ◽  
Michael Nevels
Keyword(s):  
Dna Replication ◽  
Dna Synthesis ◽  
Histone Modification ◽  
Dna Polymerase ◽  
Human Cytomegalovirus ◽  
Viral Genome ◽  
Histone H3 ◽  
Viral Dna ◽  
The Impact ◽  
Preferential Incorporation

In the nuclei of permissive cells, human cytomegalovirus genomes form nucleosomal structures initially resembling heterochromatin but gradually switching to a euchromatin-like state. This switch is characterized by a decrease in histone H3 K9 methylation and a marked increase in H3 tail acetylation and H3 K4 methylation across the viral genome. We used ganciclovir and a mutant virus encoding a reversibly destabilized DNA polymerase to examine the impact of DNA replication on histone modification dynamics at the viral chromatin. The changes in H3 tail acetylation and H3 K9 methylation proceeded in a DNA replication-independent fashion. In contrast, the increase in H3 K4 methylation proved to depend widely on viral DNA synthesis. Consistently, labeling of nascent DNA using “click chemistry” revealed preferential incorporation of methylated H3 K4 into viral (but not cellular) chromatin during or following DNA replication. This study demonstrates largely selective epigenetic tagging of postreplicative human cytomegalovirus chromatin.

scholarly journals Nuclear Import of the Retrotransposon Tf1 Is Governed by a Nuclear Localization Signal That Possesses a Unique Requirement for the FXFG Nuclear Pore Factor Nup124p

2000 ◽  
Vol 20 (20) ◽  
pp. 7798-7812 ◽  
Author(s):  
Van-Dinh Dang ◽  
Henry L. Levin
Keyword(s):  
Amino Acid ◽  
Nuclear Envelope ◽  
Nuclear Localization ◽  
Nuclear Import ◽  
Heterologous Protein ◽  
Simian Virus 40 ◽  
Nuclear Pore ◽  
Surprising Result ◽  
Gag Protein ◽  
Nuclear Localization Signals

ABSTRACT Retroviruses, such as human immunodeficiency virus, that infect nondividing cells generate integration precursors that must cross the nuclear envelope to reach the host genome. As a model for retroviruses, we investigated the nuclear entry of Tf1, a long-terminal-repeat-containing retrotransposon of the fission yeastSchizosaccharomyces pombe. Because the nuclear envelope of yeasts remains intact throughout the cell cycle, components of Tf1 must be transported through the envelope before integration can occur. The nuclear localization of the Gag protein of Tf1 is different from that of other proteins tested in that it has a specific requirement for the FXFG nuclear pore factor, Nup124p. Using extensive mutagenesis, we found that Gag contained three nuclear localization signals (NLSs) which, when included individually in a heterologous protein, were sufficient to direct nuclear import. In the context of the intact transposon, mutations in the NLS that mapped to the first 10 amino acid residues of Gag significantly impaired Tf1 retrotransposition and abolished nuclear localization of Gag. Interestingly, this NLS activity in the heterologous protein was specifically dependent upon the presence of Nup124p. Deletion analysis of heterologous proteins revealed the surprising result that the residues in Gag with the NLS activity were independent from the residues that conveyed the requirement for Nup124p. In fact, a fragment of Gag that lacked NLS activity, residues 10 to 30, when fused to a heterologous protein, was sufficient to cause the classical NLS of simian virus 40 to require Nup124p for nuclear import. Within the context of the current understanding of nuclear import, these results represent the novel case of a short amino acid sequence that specifies the need for a particular nuclear pore complex protein.

scholarly journals Autoantibodies from patients with primary biliary cirrhosis recognize a restricted region within the cytoplasmic tail of nuclear pore membrane glycoprotein Gp210.

1993 ◽  
Vol 178 (6) ◽  
pp. 2237-2242 ◽  
Author(s):  
R E Nickowitz ◽  
H J Worman
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Primary Biliary Cirrhosis ◽  
Antigenic Determinants ◽  
Nuclear Pore ◽  
Biliary Cirrhosis ◽  
Amino Terminal ◽  
Terminal Domain ◽  
Carboxy Terminal ◽  
Amino Terminal Domain

Patients with primary biliary cirrhosis (PBC) frequently have autoantibodies against a 210-kD integral glycoprotein of the nuclear envelope pore membrane. This protein, termed gp210, has a 1,783-amino acid amino-terminal domain located in the perinuclear space, a 20-amino acid transmembrane segment, and a 58-amino acid cytoplasmic carboxy-terminal tail. We now demonstrate that autoantibodies from 25 patients with PBC that recognize gp210 react with the cytoplasmic carboxy-terminal tail while none react with unmodified linear epitopes in the amino-terminal domain. The epitope(s) recognized by autoantibodies from all 25 patients is contained within a stretch of 15 amino acids. The recognized amino acid sequence is homologous to the protein products of the Escherichia coli mutY gene and Salmonella typhimurium mutB gene with an exact identity of six consecutive amino acids, suggesting that anti-gp210 antibodies may arise by molecular mimicry of bacterial antigenic determinants.

scholarly journals Molecular Basis for the Anchoring of Proto-Oncoprotein Nup98 to the Cytoplasmic Face of the Nuclear Pore Complex

2012 ◽  
Vol 419 (5) ◽  
pp. 330-346 ◽  
Author(s):  
Tobias Stuwe ◽  
Lennart Schada von Borzyskowski ◽  
Andrew M. Davenport ◽  
André Hoelz
Keyword(s):  
Nuclear Pore Complex ◽  
Molecular Basis ◽  
Nuclear Pore ◽  
Cytoplasmic Face

scholarly journals The E3 ubiquitin ligase Mind bomb 1 enhances nuclear import of viral DNA by inactivating a virion linchpin protein that suppresses exposure of virion pathogen-associated molecular patterns

2020 ◽  
Author(s):  
Michael Bauer ◽  
Alfonso Gomez-Gonzalez ◽  
Maarit Suomalainen ◽  
Silvio Hemmi ◽  
Urs F. Greber
Keyword(s):  
Nuclear Import ◽  
Core Protein ◽  
Wild Type Virus ◽  
Viral Gene ◽  
Dual Function ◽  
Nuclear Pore ◽  
Wild Type ◽  
Viral Dna ◽  
Dna Release ◽  
Molecular Patterns

ABSTRACTIn eukaryotic cells, genomes from incoming DNA viruses mount two opposing reactions, viral gene expression and innate immune response, depending on genome exposure (uncoating) to either RNA-polymerases or DNA sensors. Here we show that adenovirus particles contain a tunable linchpin protein with a dual function: response to host cues for scheduled DNA release into the nucleus, and innate immunity suppression by preventing unscheduled DNA release. Scheduled DNA release required the proteasome and ubiquitination of the viral core protein V. Cells lacking the E3 ligase Mind bomb 1 (Mib1) were resistant to wild-type adenovirus infection. Viruses lacking protein V or bearing non-ubiquitinable protein V, however, readily infected Mib1 knockout cells, yet were less infectious than wild-type virus. Their genomes were poorly imported into the nucleus and remained uncoated in the cytosol, thereby enhancing chemokine and interferon production through the DNA sensor cGAS. Our data uncover how the ubiquitin-proteasome system controls the function of a virion linchpin protein suppressing pathogen-associated molecular patterns and triggers viral DNA uncoating at the nuclear pore complex for nuclear import and infection.

scholarly journals Optimality of the spontaneous prophage induction rate

2019 ◽  
Author(s):  
Michael Cortes ◽  
Jonathan Krog ◽  
Gábor Balázsi
Keyword(s):  
Cell Death ◽  
Growth Rates ◽  
Viral Genome ◽  
Evolutionary Dynamics ◽  
Bacterial Cells ◽  
Viral Dna ◽  
Prophage Induction ◽  
Copy Numbers ◽  
Bacterial Viruses ◽  
The Impact

AbstractLysogens are bacterial cells that have survived after being infected by bacterial viruses called bacteriophages. Instead of being killed by the virus, the infected cell survives by integrating the viral DNA into its own genome. This is only possible with “temperate” bacteriophages which do not always lyse their host to reproduce, but sometimes replicate passively using the lysogenic pathway. After an infection resulting in lysogeny, the lysogen continues to grow and divide normally, seemingly unaffected by the integrated viral genome which is now referred to as a prophage. However, the prophage can have an impact on the host’s phenotype and overall fitness in certain environments. This makes competition between the lysogen and its nonlysogen counterpart possible because both cells have different genomes and potentially different growth rates. Additionally, the prophages within the lysogens are capable of spontaneously reverting back to the lytic pathway via spontaneous prophage induction (SPI), causing death of the lysogen and the release of new progeny phages. These new phages can then lyse or lysogenize other susceptible nonlysogens, thereby impacting the competition between lysogens and nonlysogens. In a scenario with differing growth rates, it is not clear whether SPI would be beneficial or detrimental to the lysogens since it directly causes cell death but also attacks nonlysogenic competitiors, either lysing or lysogenizing them. In this work we study the evolutionary dynamics of a mixture of lysogens and nonlysogens and derive general conditions on the rate of SPI resulting in lysogens displacing nonlysogens. We show that there exists an optimal SPI rate, and apply the model to bacteriophage λ. We find that the model can explain why the experimentally measured SPI rate for phage λ is so low. We also investigate the impact of stochasticity and conclude that even at low copy numbers the SPI rate can still be fairly low while still providing an advantage to the lysogens.

scholarly journals The Contribution of Homocysteine Metabolism Disruption to Endothelial Dysfunction: State-of-the-Art

2019 ◽  
Vol 20 (4) ◽  
pp. 867 ◽  
Author(s):  
Ruben Esse ◽  
Madalena Barroso ◽  
Isabel Tavares de Almeida ◽  
Rita Castro
Keyword(s):  
Amino Acid ◽  
Endothelial Dysfunction ◽  
Molecular Basis ◽  
Methylation Status ◽  
Lipoprotein Metabolism ◽  
Negative Regulator ◽  
Vascular Lesions ◽  
Antioxidant Systems ◽  
Vascular Toxicity ◽  
The Impact

Homocysteine (Hcy) is a sulfur-containing non-proteinogenic amino acid formed during the metabolism of the essential amino acid methionine. Hcy is considered a risk factor for atherosclerosis and cardiovascular disease (CVD), but the molecular basis of these associations remains elusive. The impairment of endothelial function, a key initial event in the setting of atherosclerosis and CVD, is recurrently observed in hyperhomocysteinemia (HHcy). Various observations may explain the vascular toxicity associated with HHcy. For instance, Hcy interferes with the production of nitric oxide (NO), a gaseous master regulator of endothelial homeostasis. Moreover, Hcy deregulates the signaling pathways associated with another essential endothelial gasotransmitter: hydrogen sulfide. Hcy also mediates the loss of critical endothelial antioxidant systems and increases the intracellular concentration of reactive oxygen species (ROS) yielding oxidative stress. ROS disturb lipoprotein metabolism, contributing to the growth of atherosclerotic vascular lesions. Moreover, excess Hcy maybe be indirectly incorporated into proteins, a process referred to as protein N-homocysteinylation, inducing vascular damage. Lastly, cellular hypomethylation caused by build-up of S-adenosylhomocysteine (AdoHcy) also contributes to the molecular basis of Hcy-induced vascular toxicity, a mechanism that has merited our attention in particular. AdoHcy is the metabolic precursor of Hcy, which accumulates in the setting of HHcy and is a negative regulator of most cell methyltransferases. In this review, we examine the biosynthesis and catabolism of Hcy and critically revise recent findings linking disruption of this metabolism and endothelial dysfunction, emphasizing the impact of HHcy on endothelial cell methylation status.

scholarly journals STING facilitates nuclear import of herpesvirus genome during infection

2021 ◽  
Vol 118 (33) ◽  
pp. e2108631118
Author(s):  
Yujin Hong ◽  
Heena Jeong ◽  
Kiwon Park ◽  
Sungwon Lee ◽  
Jae Youn Shim ◽  
...  
Keyword(s):  
Nuclear Import ◽  
Viral Genome ◽  
Early Stage ◽  
Viral Gene Expression ◽  
Viral Capsid ◽  
Viral Gene ◽  
Nuclear Pore ◽  
Physical Interaction ◽  
Herpes Simplex Virus 1 ◽  
Successful Infection

Once inside the host cell, DNA viruses must overcome the physical barrier posed by the nuclear envelope to establish a successful infection. The mechanism underlying this process remains unclear. Here, we show that the herpesvirus exploits the immune adaptor stimulator of interferon genes (STING) to facilitate nuclear import of the viral genome. Following the entry of the viral capsid into the cell, STING binds the viral capsid, mediates capsid docking to the nuclear pore complex via physical interaction, and subsequently enables accumulation of the viral genome in the nucleus. Silencing STING in human cytomegalovirus (HCMV)-susceptible cells inhibited nuclear import of the viral genome and reduced the ensuing viral gene expression. Overexpressing STING increased the host cell’s susceptibility to HCMV and herpes simplex virus 1 by improving the nuclear delivery of viral DNA at the early stage of infection. These observations suggest that the proviral activity of STING is conserved and exploited by the herpesvirus family. Intriguingly, in monocytes, which act as latent reservoirs of HCMV, STING deficiency negatively regulated the establishment of HCMV latency and reactivation. Our findings identify STING as a proviral host factor regulating latency and reactivation of herpesviruses.

scholarly journals BGLF4 Kinase Modulates the Structure and Transport Preference of the Nuclear Pore Complex To Facilitate Nuclear Import of Epstein-Barr Virus Lytic Proteins

2014 ◽  
Vol 89 (3) ◽  
pp. 1703-1718 ◽  
Author(s):  
Chou-Wei Chang ◽  
Chung-Pei Lee ◽  
Mei-Tzu Su ◽  
Ching-Hwa Tsai ◽  
Mei-Ru Chen
Keyword(s):  
Dna Replication ◽  
Nuclear Import ◽  
Epstein Barr Virus ◽  
Lytic Replication ◽  
Nuclear Pore ◽  
Nuclear Targeting ◽  
Viral Dna ◽  
Viral Dna Replication ◽  
Barr Virus ◽  
Epstein Barr

ABSTRACTBGLF4 kinase, the only Ser/Thr protein kinase encoded by the Epstein-Barr virus (EBV) genome, phosphorylates multiple viral and cellular substrates to optimize the cellular environment for viral DNA replication and the nuclear egress of nucleocapsids. Previously, we found that nuclear targeting of BGLF4 is through direct interaction with the FG repeat-containing nucleoporins (FG-Nups) Nup62 and Nup153 independently of cytosolic transport factors. Here, we investigated the regulatory effects of BGLF4 on the structure and biological functions of the nuclear pore complex (NPC). In EBV-positive NA cells, the distribution of FG-Nups was modified during EBV reactivation. In transfected cells, BGLF4 changed the staining pattern of Nup62 and Nup153 in a kinase activity-dependent manner. Detection with anti-phospho-Ser/Thr-Pro MPM-2 antibody demonstrated that BGLF4 induced the phosphorylation of Nup62 and Nup153. The nuclear targeting of importin β was attenuated in the presence of BGLF4, leading to inhibition of canonical nuclear localization signal (NLS)-mediated nuclear import. Anin vitronuclear import assay revealed that BGLF4 induced the nuclear import of larger molecules. Notably, we found that BGLF4 promoted the nuclear import of several non-NLS-containing EBV proteins, including the viral DNA-replicating enzymes BSLF1, BBLF2/3, and BBLF4 and the major capsid protein (VCA), in cotransfected cells. The data presented here suggest that BGLF4 interferes with the normal functions of Nup62 and Nup153 and preferentially helps the nuclear import of viral proteins for viral DNA replication and assembly. In addition, the nuclear import-promoting activity was found in cells expressing the BGLF4 homologs of another two gammaherpesviruses but not those from alpha- and betaherpesviruses.IMPORTANCEDuring lytic replication, many EBV genome-encoded proteins need to be transported into the nucleus, not only for viral DNA replication but also for the assembly of nucleocapsids. Because nuclear pore complexes are effective gateways that control nucleocytoplasmic traffic, most EBV proteins without canonical NLSs are retained in the cytoplasm until they form complexes with their NLS-containing partners for nuclear targeting. In this study, we found that EBV BGLF4 protein kinase interacts with the Nup62 and Nup153 and induces the redistribution of FG-Nups. BGLF4 modulates the function of the NPC to inhibit the nuclear import of host NLS-containing proteins. Simultaneously, the nuclear import of non-NLS-containing EBV lytic proteins was enhanced, possibly through phosphorylation of Nup62 and Nup153, nuclear pore dilation, or microtubule reorganization. Overall, our data suggest that BGLF4-induced modification of nuclear pore transport may block nuclear targeting of cellular proteins and increase the import of viral proteins to promote viral lytic replication.

scholarly journals Analysis of the Viral Elements Required in the Nuclear Import of HIV-1 DNA

2009 ◽  
Vol 84 (2) ◽  
pp. 729-739 ◽  
Author(s):  
Lise Rivière ◽  
Jean-Luc Darlix ◽  
Andrea Cimarelli
Keyword(s):  
Nuclear Import ◽  
Matrix Protein ◽  
Active Phase ◽  
Cell Types ◽  
Target Cells ◽  
Nuclear Pore ◽  
Viral Dna ◽  
The Matrix ◽  
Central Polypurine Tract ◽  
Hiv 1

ABSTRACT HIV-1 possesses an exquisite ability to infect cells independently from their cycling status by undergoing an active phase of nuclear import through the nuclear pore. This property has been ascribed to the presence of karyophilic elements present in viral nucleoprotein complexes, such as the matrix protein (MA); Vpr; the integrase (IN); and a cis-acting structure present in the newly synthesized DNA, the DNA flap. However, their role in nuclear import remains controversial at best. In the present study, we carried out a comprehensive analysis of the role of these elements in nuclear import in a comparison between several primary cell types, including stimulated lymphocytes, macrophages, and dendritic cells. We show that despite the fact that none of these elements is absolutely required for nuclear import, disruption of the central polypurine tract-central termination sequence (cPPT-CTS) clearly affects the kinetics of viral DNA entry into the nucleus. This effect is independent of the cell cycle status of the target cells and is observed in cycling as well as in nondividing primary cells, suggesting that nuclear import of viral DNA may occur similarly under both conditions. Nonetheless, this study indicates that other components are utilized along with the cPPT-CTS for an efficient entry of viral DNA into the nucleus.

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