A Single Herpesvirus Protein Can Mediate Vesicle Formation in the Nuclear Envelope

Lorenz, Michael G.; Vollmer, Benjamin; Unsay, Joseph D.; Klupp, Barbara G.; García‐Sáez, Ana J.; Mettenleiter, Thomas C.; Antonin, Wolfram

doi:10.1074/jbc.m114.627521

Cited by 72 publications

(102 citation statements)

References 73 publications

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“…By reconstituting the budding process in vitro using the purified NEC and synthetic liposomes, we showed that the HSV-1 NEC has an intrinsic ability to mediate budding and scission (10). This finding was subsequently confirmed for the pseudorabies virus NEC (11).…”

mentioning

confidence: 61%

The Great (Nuclear) Escape: New Insights into the Role of the Nuclear Egress Complex of Herpesviruses

Bigalke

Heldwein

2015

J Virol

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Herpesviruses are unusual among enveloped viruses because they bud twice yet acquire a single envelope. They are also the only known viruses that bud into the nuclear envelope. We discovered that the herpesvirus nuclear egress complex could bud membranes without the help of other proteins by forming a coat-like hexagonal scaffold inside the budding membrane. This finding raises the possibility that a phenotypically similar nuclear export of large RNAs is cargo driven. Most enveloped viruses acquire their envelopes by capsid budding into a cellular membrane. Some viruses, such as HIV or influenza virus, bud into the plasma membrane while other viruses, such as flaviviruses, bud into intracellular membranes such as the endoplasmic reticulum, the Golgi compartment, or others, depending on the virus. Herpesviruses represent an unusual case. Despite having a single envelope, these double-stranded DNA viruses undergo two rounds of budding; they bud first into the inner nuclear membrane (INM) and later into cytoplasmic membranes derived from the trans-Golgi network or early endosomes (1). This also makes them the only known viruses to use the nuclear membrane for budding. Yet, the envelope acquired during the first budding event at the INM does not end up in the mature viral particle. Only the second and final round of budding in the cytosol generates the single-layer envelope of the mature virus. Instead, the unusual nuclear budding allows the viral capsid to escape from the nucleus.Herpesvirus genomes are replicated and encapsidated in the nucleus. The nucleus is surrounded by the INM and outer nuclear membrane (ONM), and most traffic in and out of the nucleus occurs through the nuclear pores. The diameter of herpesvirus capsids (125 nm in HSV-1) is considerably larger than that of the nuclear pore channels (52 nm), and thus, the capsids cannot fit through them. To escape from the nucleus, nucleocapsids bud into the INM, forming perinuclear immature viral particlesintermediates that are different from the mature, infectious viruses-that then fuse with the ONM, releasing the naked capsids into the cytosol (Fig. 1). As a result of this process, termed nuclear egress, nucleocapsids are translocated from the nucleus into the cytoplasm, where they mature into final, infectious virions.Efficient exit of nascent capsids from the nucleus requires the virus-encoded nuclear egress complex (NEC) (reviewed in reference 1). The NEC consists of conserved viral proteins UL31 and UL34. UL34 is anchored to the INM by a C-terminal transmembrane (TM) helix with three residues extending into the perinuclear space (3). UL31 is a nuclear phosphoprotein that localizes to the INM through interaction with UL34 (4, 5). Formation of the NEC is a prerequisite for efficient nuclear egress. In the absence of either UL31 or UL34, viral replication is impaired and most capsids are retained in the nucleus (6, 7). The NEC is also sufficient to drive the formation of perinuclear vesicles in transfected cells (8,9), which demonstrated that UL31 and UL3...

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mentioning

confidence: 61%

The Great (Nuclear) Escape: New Insights into the Role of the Nuclear Egress Complex of Herpesviruses

Bigalke

Heldwein

2015

J Virol

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“…Unlabeled and uniformly labeled ( 15 N, 13 C, and/or 2 H) samples of C-terminal truncations of UL50, UL53, M50, and M53 as well as alanine mutants of UL50 and M50 were derived from constructs created and expressed using methods similar to those described in the work by Sam et al (30). Isoleucine, leucine, valine-methyl-labeled samples were prepared using α-ketobutyrate and α-ketoisovalerate precursors as described (41,42).…”

Section: Methodsmentioning

confidence: 99%

“…It is generally accepted that, after assembly in the nucleus, the viral nucleocapsid undergoes envelopment to cross the inner nuclear membrane (INM) followed by deenvelopment to cross the outer nuclear membrane, resulting in release into the cytoplasm for continuation of the virion maturation process (4). Nuclear egress is orchestrated by a highly conserved, heterodimeric nuclear egress complex (NEC), which recruits one or more protein kinases to disrupt the nuclear lamina, permitting access of nucleocapsids to the INM, where the NEC induces budding of the nucleocapsid into the perinuclear space (5)(6)(7)(8)(9)(10)(11)(12)(13). In HCMV, the NEC is comprised of UL50, which is an INM protein, and UL53, which is a nucleoplasmic protein that is brought to the INM by its interaction with UL50.…”

mentioning

confidence: 99%

Structure of a herpesvirus nuclear egress complex subunit reveals an interaction groove that is essential for viral replication

Leigh

Sharma

Mansueto

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

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Herpesviruses require a nuclear egress complex (NEC) for efficient transit of nucleocapsids from the nucleus to the cytoplasm. The NEC orchestrates multiple steps during herpesvirus nuclear egress, including disruption of nuclear lamina and particle budding through the inner nuclear membrane. In the important human pathogen human cytomegalovirus (HCMV), this complex consists of nuclear membrane protein UL50, and nucleoplasmic protein UL53, which is recruited to the nuclear membrane through its interaction with UL50. Here, we present an NMR-determined solution-state structure of the murine CMV homolog of UL50 (M50; residues 1-168) with a strikingly intricate protein fold that is matched by no other known protein folds in its entirety. Using NMR methods, we mapped the interaction of M50 with a highly conserved UL53-derived peptide, corresponding to a segment that is required for heterodimerization. The UL53 peptide binding site mapped onto an M50 surface groove, which harbors a large cavity. Point mutations of UL50 residues corresponding to surface residues in the characterized M50 heterodimerization interface substantially decreased UL50-UL53 binding in vitro, eliminated UL50-UL53 colocalization, prevented disruption of nuclear lamina, and halted productive virus replication in HCMV-infected cells. Our results provide detailed structural information on a key protein-protein interaction involved in nuclear egress and suggest that NEC subunit interactions can be an attractive drug target.H erpesviruses encompass a large family of infectious agents, including important veterinary and human pathogens (1). Among the latter is human cytomegalovirus (HCMV), which can cause serious disease, particularly in immunocompromised individuals and newborns (2). Despite the importance of HCMV in these medically vulnerable populations, currently available treatment options suffer from issues with toxicities, drug resistance, and/or pharmacokinetics (2, 3), motivating the identification of new drug targets.All herpesviruses of mammals, birds, and reptiles undergo a remarkable process known as nuclear egress as part of the viral lifecycle. It is generally accepted that, after assembly in the nucleus, the viral nucleocapsid undergoes envelopment to cross the inner nuclear membrane (INM) followed by deenvelopment to cross the outer nuclear membrane, resulting in release into the cytoplasm for continuation of the virion maturation process (4). Nuclear egress is orchestrated by a highly conserved, heterodimeric nuclear egress complex (NEC), which recruits one or more protein kinases to disrupt the nuclear lamina, permitting access of nucleocapsids to the INM, where the NEC induces budding of the nucleocapsid into the perinuclear space (5-13). In HCMV, the NEC is comprised of UL50, which is an INM protein, and UL53, which is a nucleoplasmic protein that is brought to the INM by its interaction with UL50. These two proteins and their murine CMV (MCMV) homologues, M50 and M53, are essential for replication and nuclear egress (8, 14-17) of ...

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“…It is possible that Nup153 is localized to the NE due to interactions with integral inner nuclear membrane proteins or lamins, proteins that underlay and stabilize the NE, but it could also bind directly to the lipid bilayer. To test for a direct membrane interaction we incubated the purified recombinant N-terminal region comprising the first 149 aa of Xenopus laevis Nup153 with small unilamellar liposomes with a NE lipid composition (Lorenz et al, 2015). Due to their density, lipid vesicles float up through a sucrose gradient.…”

Section: Nup153 Interacts Via Its N Terminus Directly With Membranesmentioning

confidence: 99%

Nup153 Recruits the Nup107-160 Complex to the Inner Nuclear Membrane for Interphasic Nuclear Pore Complex Assembly

et al. 2015

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In metazoa, nuclear pore complexes (NPCs) are assembled from constituent nucleoporins by two distinct mechanisms: in the re-forming nuclear envelope at the end of mitosis and into the intact nuclear envelope during interphase. Here, we show that the nucleoporin Nup153 is required for NPC assembly during interphase but not during mitotic exit. It functions in interphasic NPC formation by binding directly to the inner nuclear membrane via an N-terminal amphipathic helix. This binding facilitates the recruitment of the Nup107-160 complex, a crucial structural component of the NPC, to assembly sites. Our work further suggests that the nuclear transport receptor transportin and the small GTPase Ran regulate the interaction of Nup153 with the membrane and, in this way, direct pore complex assembly to the nuclear envelope during interphase.

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A Single Herpesvirus Protein Can Mediate Vesicle Formation in the Nuclear Envelope

Cited by 72 publications

References 73 publications

The Great (Nuclear) Escape: New Insights into the Role of the Nuclear Egress Complex of Herpesviruses

The Great (Nuclear) Escape: New Insights into the Role of the Nuclear Egress Complex of Herpesviruses

Structure of a herpesvirus nuclear egress complex subunit reveals an interaction groove that is essential for viral replication

Nup153 Recruits the Nup107-160 Complex to the Inner Nuclear Membrane for Interphasic Nuclear Pore Complex Assembly

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