Oestrogen blocks the nuclear entry of SOX9 in the developing gonad of a marsupial mammal

HIV-1 can infect non-dividing cells. The nuclear envelope therefore represents a barrier that HIV-1 must traverse in order to gain access to the host cell chromatin for integration. Hence, nuclear entry is a critical step in the early stages of HIV-1 replication. Following membrane fusion, the viral capsid (CA) lattice, which forms the outer face of the retroviral core, makes numerous interactions with cellular proteins that orchestrate the progress of HIV-1 through the replication cycle. The ability of CA to interact with nuclear pore proteins and other host factors around the nuclear pore determines whether nuclear entry occurs. Uncoating, the process by which the CA lattice opens and/or disassembles, is another critical step that must occur prior to integration. Both early and delayed uncoating have detrimental effects on viral infectivity. How uncoating relates to nuclear entry is currently hotly debated. Recent technological advances have led to intense discussions about the timing, location, and requirements for uncoating and have prompted the field to consider alternative uncoating scenarios that presently focus on uncoating at the nuclear pore and within the nuclear compartment. This review describes recent advances in the study of HIV-1 nuclear entry, outlines the interactions of the retroviral CA protein, and discusses the challenges of investigating HIV-1 uncoating.

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Targeting novel LSD1-dependent ACE2 demethylation domains inhibits SARS-CoV-2 replication

Cell Discovery ◽

10.1038/s41421-021-00279-w ◽

2021 ◽

Vol 7 (1) ◽

Author(s):

Wen Juan Tu ◽

Robert D. McCuaig ◽

Michelle Melino ◽

Daniel J. Rawle ◽

Thuy T. Le ◽

...

Keyword(s):

Viral Replication ◽

Treatment Options ◽

Critical Role ◽

Post Exposure Prophylaxis ◽

Nuclear Entry ◽

Importin Α ◽

Active Transcription ◽

Nuclear Shuttling ◽

Asymptomatic Phase ◽

Exposure Prophylaxis

AbstractTreatment options for COVID-19 remain limited, especially during the early or asymptomatic phase. Here, we report a novel SARS-CoV-2 viral replication mechanism mediated by interactions between ACE2 and the epigenetic eraser enzyme LSD1, and its interplay with the nuclear shuttling importin pathway. Recent studies have shown a critical role for the importin pathway in SARS-CoV-2 infection, and many RNA viruses hijack this axis to re-direct host cell transcription. LSD1 colocalized with ACE2 at the cell surface to maintain demethylated SARS-CoV-2 spike receptor-binding domain lysine 31 to promote virus–ACE2 interactions. Two newly developed peptide inhibitors competitively inhibited virus–ACE2 interactions, and demethylase access to significantly inhibit viral replication. Similar to some other predominantly plasma membrane proteins, ACE2 had a novel nuclear function: its cytoplasmic domain harbors a nuclear shuttling domain, which when demethylated by LSD1 promoted importin-α-dependent nuclear ACE2 entry following infection to regulate active transcription. A novel, cell permeable ACE2 peptide inhibitor prevented ACE2 nuclear entry, significantly inhibiting viral replication in SARS-CoV-2-infected cell lines, outperforming other LSD1 inhibitors. These data raise the prospect of post-exposure prophylaxis for SARS-CoV-2, either through repurposed LSD1 inhibitors or new, nuclear-specific ACE2 inhibitors.

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The nucleocapsid protein of rice stripe virus in cell nuclei of vector insect regulates viral replication

Protein & Cell ◽

10.1007/s13238-021-00822-1 ◽

2021 ◽

Author(s):

Wan Zhao ◽

Junjie Zhu ◽

Hong Lu ◽

Jiaming Zhu ◽

Fei Jiang ◽

...

Keyword(s):

Viral Replication ◽

Nucleocapsid Protein ◽

Brown Planthopper ◽

Rice Stripe Virus ◽

Host Cells ◽

Cell Nuclei ◽

Nuclear Entry ◽

Genomic Rnas ◽

Importin Α ◽

Vector Insect

AbstractRice stripe virus (RSV) transmitted by the small brown planthopper causes severe rice yield losses in Asian countries. Although viral nuclear entry promotes viral replication in host cells, whether this phenomenon occurs in vector cells remains unknown. Therefore, in this study, we systematically evaluated the presence and roles of RSV in the nuclei of vector insect cells. We observed that the nucleocapsid protein (NP) and viral genomic RNAs were partially transported into vector cell nuclei by utilizing the importin α nuclear transport system. When blocking NP nuclear localization, cytoplasmic RSV accumulation significantly increased. In the vector cell nuclei, NP bound the transcription factor YY1 and affected its positive regulation to FAIM. Subsequently, decreased FAIM expression triggered an antiviral caspase-dependent apoptotic reaction. Our results reveal that viral nuclear entry induces completely different immune effects in vector and host cells, providing new insights into the balance between viral load and the immunity pressure in vector insects.

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Post-Translational Regulation and Nuclear Entry of TIMELESS and PERIOD Are Affected in New timeless Mutant

Journal of Neuroscience ◽

10.1523/jneurosci.0993-11.2011 ◽

2011 ◽

Vol 31 (27) ◽

pp. 9982-9990 ◽

Cited By ~ 13

Author(s):

T. Hara ◽

K. Koh ◽

D. J. Combs ◽

A. Sehgal

Keyword(s):

Translational Regulation ◽

Nuclear Entry

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Baculovirus Transregulator IE1 Requires a Dimeric Nuclear Localization Element for Nuclear Import and Promoter Activation

Journal of Virology ◽

10.1128/jvi.76.18.9505-9515.2002 ◽

2002 ◽

Vol 76 (18) ◽

pp. 9505-9515 ◽

Cited By ~ 39

Author(s):

Victoria A. Olson ◽

Justin A. Wetter ◽

Paul D. Friesen

Keyword(s):

Nuclear Localization ◽

Nuclear Import ◽

Direct Interaction ◽

Productive Infection ◽

Homologous Region ◽

Wild Type ◽

Nuclear Entry ◽

Early Protein ◽

Biochemical Fractionation ◽

Localization Element

ABSTRACT Immediate-early protein IE1 is a principal regulator of viral transcription and a contributor to origin-specific DNA replication of the baculovirus Autographa californica multicapsid nucleopolyhedrovirus (AcMNPV). Since these viral functions involve interaction of dimeric IE1 with palindromic homologous region (hr) enhancer-origin elements of the AcMNPV genome within the nucleus, it is presumed that proper nuclear transport of IE1 is essential for productive infection. To investigate the mechanisms of IE1 nuclear import, we analyzed the effect of site-directed mutations on IE1 subcellular distribution. As demonstrated by fluorescence microscopy and biochemical fractionation of plasmid-transfected cells, wild-type IE1 localized predominantly to the nucleus. Substitution or deletion of amino acid residues within a positively charged domain (residues 534 to 538) adjacent to IE1's oligomerization motif impaired nuclear import and caused loss of transactivation. Moreover, upon coexpression, these import-defective mutations prevented nuclear entry of wild-type IE1. In contrast, double-mutated IE1 defective for both nuclear import and dimerization failed to block nuclear entry or transactivation by wild-type IE1. Thus, import-defective IE1 dominantly interfered with wild-type IE1 by direct interaction and cytosolic trapping. Collectively, our data indicate that the small basic domain encompassing residues R537 and R538 constitutes a novel nuclear localization element that functions only upon IE1 dimerization. These findings support a model wherein IE1 oligomerizes within the cytosol as a prerequisite for nuclear entry and subsequent high-affinity interaction with the symmetrical binding sites comprising AcMNPV hr enhancer-origin elements.

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PF74 Inhibits HIV-1 Integration by Altering the Composition of the Preintegration Complex

Journal of Virology ◽

10.1128/jvi.01741-18 ◽

2018 ◽

Vol 93 (6) ◽

Cited By ~ 11

Author(s):

Muthukumar Balasubramaniam ◽

Jing Zhou ◽

Amma Addai ◽

Phillip Martinez ◽

Jui Pandhare ◽

...

Keyword(s):

Reverse Transcription ◽

Integrase Inhibitor ◽

Antiviral Effect ◽

Inhibitory Effect ◽

Clear Understanding ◽

Nuclear Entry ◽

Preintegration Complex ◽

Gradient Based ◽

Hiv 1

ABSTRACTThe HIV-1 capsid protein (CA) facilitates reverse transcription and nuclear entry of the virus. However, CA’s role in post-nuclear entry steps remains speculative. We describe a direct link between CA and integration by employing the capsid inhibitor PF74 as a probe coupled with the biochemical analysis of HIV-1 preintegration complexes (PICs) isolated from acutely infected cells. At a low micromolar concentration, PF74 potently inhibited HIV-1 infection without affecting reverse transcription. Surprisingly, PF74 markedly reduced proviral integration owing to inhibition of nuclear entry and/or integration. However, a 2-fold reduction in nuclear entry by PF74 did not quantitatively correlate with the level of antiviral activity. Titration of PF74 against the integrase inhibitor raltegravir showed an additive antiviral effect that is dependent on a block at the post-nuclear entry step. PF74’s inhibitory effect was not due to the formation of defective viral DNA ends or a delay in integration, suggesting that the compound inhibits PIC-associated integration activity. Unexpectedly, PICs recovered from cells infected in the presence of PF74 exhibited elevated integration activity. PF74’s effect on PIC activity is CA specific since the compound did not increase the integration activity of PICs of a PF74-resistant HIV-1 CA mutant. Sucrose gradient-based fractionation studies revealed that PICs assembled in the presence of PF74 contained lower levels of CA, suggesting a negative association between CA and PIC-associated integration activity. Finally, the addition of a CA-specific antibody or PF74 inhibited PIC-associated integration activity. Collectively, our results demonstrate that PF74’s targeting of PIC-associated CA results in impaired HIV-1 integration.IMPORTANCEAntiretroviral therapy (ART) that uses various combinations of small molecule inhibitors has been highly effective in controlling HIV. However, the drugs used in the ART regimen are expensive, cause side effects, and face viral resistance. The HIV-1 CA plays critical roles in the virus life cycle and is an attractive therapeutic target. While currently there is no CA-based therapy, highly potent CA-specific inhibitors are being developed as a new class of antivirals. Efforts to develop a CA-targeted therapy can be aided through a clear understanding of the role of CA in HIV-1 infection. CA is well established to coordinate reverse transcription and nuclear entry of the virus. However, the role of CA in post-nuclear entry steps of HIV-1 infection is poorly understood. We show that a CA-specific drug PF74 inhibits HIV-1 integration revealing a novel role of this multifunctional viral protein in a post-nuclear entry step of HIV-1 infection.

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Novel Hepatitis B Virus Capsid-Targeting Antiviral That Aggregates Core Particles and Inhibits Nuclear Entry of Viral Cores

ACS Infectious Diseases ◽

10.1021/acsinfecdis.8b00235 ◽

2018 ◽

Vol 5 (5) ◽

pp. 750-758 ◽

Cited By ~ 1

Author(s):

Andrew D. Huber ◽

Dallas L. Pineda ◽

Dandan Liu ◽

Kelsey N. Boschert ◽

Anna T. Gres ◽

...

Keyword(s):

Hepatitis B Virus ◽

Hepatitis B ◽

Nuclear Entry ◽

Virus Capsid ◽

B Virus ◽

Core Particles

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No Enhancement of Nuclear Entry by Direct Conjugation of a Nuclear Localization Signal Peptide to Linearized DNA

Bioconjugate Chemistry ◽

10.1021/bc034075e ◽

2003 ◽

Vol 14 (6) ◽

pp. 1197-1202 ◽

Cited By ~ 68

Author(s):

Mitsuhide Tanimoto ◽

Hiroyuki Kamiya ◽

Noriaki Minakawa ◽

Akira Matsuda ◽

Hideyoshi Harashima

Keyword(s):

Nuclear Localization ◽

Signal Peptide ◽

Nuclear Localization Signal ◽

Nuclear Entry ◽

Localization Signal

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TNPO3-mediated nuclear entry of the Rous sarcoma virus Gag protein is independent of the cargo-binding domain

10.1101/2020.03.12.989608 ◽

2020 ◽

Author(s):

Breanna L. Rice ◽

Matthew S. Stake ◽

Leslie J. Parent

Keyword(s):

Nuclear Import ◽

Rous Sarcoma Virus ◽

Binding Domain ◽

Nuclear Entry ◽

Gag Protein ◽

Nuclear Localization Signals ◽

Rous Sarcoma ◽

Importin Α ◽

Sarcoma Virus ◽

Cargo Binding

AbstractRetroviral Gag polyproteins orchestrate the assembly and release of nascent virus particles from the plasma membranes of infected cells. Although it was traditionally thought that Gag proteins trafficked directly from the cytosol to the plasma membrane, we discovered that the oncogenic avian alpharetrovirus Rous sarcoma virus (RSV) Gag protein undergoes transient nucleocytoplasmic transport as an intrinsic step in virus assembly. Using a genetic approach in yeast, we identified three karyopherins that engage the two independent nuclear localization signals (NLS) in Gag. The primary NLS is in the nucleocapsid (NC) domain of Gag and binds directly to importin-α, which recruits importin-β to mediate nuclear entry. The second NLS, which resides in the matrix (MA) domain, is dependent on importin-11 and transportin-3 (TNPO3), known as MTR10p and Kap120p in yeast, although it is not clear whether these import factors are independent or additive. The functionality of importin α/β and importin-11 has been verified in avian cells, whereas the role of TNPO3 has not been studied. In this report, we demonstrate that TNPO3 mediates nuclear entry of Gag and directly binds to Gag. To our surprise, this interaction did not require the cargo-binding domain of TNPO3, which typically mediates nuclear entry for other binding partners of TNPO3 including SR-domain containing splicing factors and tRNAs that re-enter the nucleus. These results suggest that RSV hijacks the host nuclear import pathway using a unique mechanism, potentially allowing other cargo to bind TNPO3 simultaneously.ImportanceRSV Gag nuclear entry is facilitated using three distinct host import factors that interact with nuclear localization signals in the Gag MA and NC domains. Here we show that the MA region is required for nuclear import of Gag through the TNPO3 pathway. Gag nuclear entry does not require the cargo binding domain of TNPO3. Understanding the molecular basis for TNPO3-mediated nuclear trafficking of the RSV Gag protein may lead to a deeper appreciation for whether different import factors play distinct roles in retrovirus replication.

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MxB sensitivity of HIV-1 is determined by a highly variable and dynamic capsid surface

eLife ◽

10.7554/elife.56910 ◽

2020 ◽

Vol 9 ◽

Cited By ~ 1

Author(s):

Richard J Miles ◽

Claire Kerridge ◽

Laura Hilditch ◽

Christopher Monit ◽

David A Jacques ◽

...

Keyword(s):

Nuclear Import ◽

Cytotoxic T Lymphocyte ◽

Cyclophilin A ◽

Conformational Flexibility ◽

Restriction Factors ◽

Nuclear Entry ◽

Linear Forms ◽

Cofactor Binding ◽

Cofactor Recruitment ◽

Hiv 1

The type one interferon induced restriction factor Myxovirus resistance B (MxB) restricts HIV-1 nuclear entry evidenced by inhibition of 2-LTR but not linear forms of viral DNA. The HIV-1 capsid is the key determinant of MxB sensitivity and cofactor binding defective HIV-1 capsid mutants P90A (defective for cyclophilin A and Nup358 recruitment) and N74D (defective for CPSF6 recruitment) have reduced dependency on nuclear transport associated cofactors, altered integration targeting preferences and are not restricted by MxB expression. This has suggested that nuclear import mechanism may determine MxB sensitivity. Here we have use genetics to separate HIV-1 nuclear import cofactor dependence from MxB sensitivity. We provide evidence that MxB sensitivity depends on HIV-1 capsid conformation, rather than cofactor recruitment. We show that depleting CPSF6 to change nuclear import pathway does not impact MxB sensitivity, but mutants that recapitulate the effect of Cyclophilin A binding on capsid conformation and dynamics strongly impact MxB sensitivity. We demonstrate that HIV-1 primary isolates have different MxB sensitivities due to cytotoxic T lymphocyte (CTL) selected differences in Gag sequence but similar cofactor dependencies. Overall our work demonstrates a complex relationship between cyclophilin dependence and MxB sensitivity likely driven by CTL escape. We propose that cyclophilin binding provides conformational flexibility to HIV-1 capsid facilitating simultaneous evasion of capsid-targeting restriction factors including TRIM5 as well as MxB.

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