scholarly journals Deubiquitinating enzyme USP21 inhibits HIV-1 replication by downregulating Tat expression

2021 ◽  
Author(s):  
Wenying Gao ◽  
Guangquan Li ◽  
Simin Zhao ◽  
Hong Wang ◽  
Chen Huan ◽  
...  
Keyword(s):  
Viral Infection ◽  
Essential Role ◽  
Elongation Factor ◽  
Accessory Proteins ◽  
Transcriptional Elongation ◽  
Mrna Levels ◽  
Cyclin T1 ◽  
Hiv Drugs ◽  
Hiv 1

Ubiquitination plays an important role in human immunodeficiency virus-1 (HIV-1) infection. HIV proteins such as Vif and Vpx mediate the degradation of the host proteins APOBEC3 and SAMHD1, respectively, through the proteasome pathway. However, whether deubiquitylating enzymes play an essential role in HIV-1 infection is largely unknown. Here, we demonstrate that the deubiquitinase, USP21, potently inhibits HIV-1 production by indirectly downregulating the expression of HIV-1 trans-activator of transcription (Tat), which is essential for transcriptional elongation in HIV-1. USP21 deubiquitylates Tat via its deubiquitinase activity, but a stronger ability to reduce Tat expression compared to Ub-KO showed that other mechanisms may contribute to USP21-mediated inhibition of Tat. Further investigation showed that USP21 downregulates cyclin T1 mRNA levels by increasing methylation of histone K9 in the promoter of cyclin T1, a subunit of the positive transcription elongation factor b (P-TEFb) that interacts with Tat and transactivation response element (TAR) and is required for transcription stimulation and Tat stability. Moreover, USP21 had no effect on the function of other HIV-1 accessory proteins, including Vif, Vpr, Vpx, and Vpu, indicating that USP21 was specific to Tat. These findings improve our understanding of USP21-mediated functional suppression of HIV-1 production. Importance Ubiquitination plays an essential role in viral infection. Deubiquitinating enzymes (DUBs) reverse ubiquitination by cleaving ubiquitins from target proteins, thereby affecting viral infection. The role of the members of the USP family, that comprises the largest subfamily of DUBs, is largely unknown in HIV-1 infection. Here, we screened a series of USP members and found that USP21 inhibits HIV-1 production by specifically targeting Tat, but not the other HIV-1 accessory proteins. Further investigations revealed that USP21 reduces Tat expression in two ways. First, USP21 deubiquitinates polyubiquitinated Tat causing Tat instability, and second USP21 reduces the mRNA levels of cyclin T1 (CycT1), an important component of P-TEFb, that leads 56 to Tat downregulation. Thus, in this study, we report a novel role of the deubiquitinase, USP21, in HIV-1 viral infection. USP21 represents a potentially useful target for the development of novel anti-HIV drugs.

scholarly journals Interaction between P-TEFb and the C-Terminal Domain of RNA Polymerase II Activates Transcriptional Elongation from Sites Upstream or Downstream of Target Genes

2002 ◽  
Vol 22 (1) ◽  
pp. 321-331 ◽  
Author(s):  
Ran Taube ◽  
Xin Lin ◽  
Dan Irwin ◽  
Koh Fujinaga ◽  
B. Matija Peterlin
Keyword(s):  
Rna Polymerase ◽  
Rna Polymerase Ii ◽  
Target Genes ◽  
Elongation Factor ◽  
Transcriptional Elongation ◽  
Cyclin T1 ◽  
Positive Transcription Elongation Factor ◽  
Terminal Domain ◽  
Activation Of Transcription

ABSTRACT Transcriptional elongation by RNA polymerase II (RNAPII) is regulated by the positive transcription elongation factor b (P-TEFb). P-TEFb is composed of Cdk9 and C-type cyclin T1 (CycT1), CycT2a, CycT2b, or CycK. The role of the C-terminal region of CycT1 and CycT2 remains unknown. In this report, we demonstrate that these sequences are essential for the activation of transcription by P-TEFb via DNA, i.e., when CycT1 is tethered upstream or downstream of promoters and coding sequences. A histidine-rich stretch, which is conserved between CycT1 and CycT2 in this region, bound the C-terminal domain of RNAPII. This binding was required for the subsequent expression of full-length transcripts from target genes. Thus, P-TEFb could mediate effects of enhancers on the elongation of transcription.

Role of HIV-1 Envelope Glycoproteins Conformation and Accessory Proteins on ADCC Responses

2015 ◽  
Vol 14 (1) ◽  
pp. 9-23 ◽  
Author(s):  
Maxime Veillette ◽  
Jonathan Richard ◽  
Marzena Pazgier ◽  
George K. Lewis ◽  
Matthew S. Parsons ◽  
...  
Keyword(s):  
Envelope Glycoproteins ◽  
Accessory Proteins ◽  
Hiv 1

scholarly journals Essential Role of Quantum Science and Nanoscience in Antiviral Strategies

2021 ◽  
Author(s):  
Mina Zare ◽  
Mika Sillanpää ◽  
Seeram Ramakrishna
Keyword(s):  
Severe Acute Respiratory Syndrome ◽  
Viral Infection ◽  
Essential Role ◽  
Quantum Science

The Severe Acute Respiratory Syndrome Coronavirus (SARS-CoV-2) caused the pandemic COVID-19 disease since December 2019 highlights the importance of developing efficient antiviral strategies to prevent and treat viral infection. Virus...

scholarly journals Phenotypic Susceptibility to Bevirimat in Isolates from HIV-1-Infected Patients without Prior Exposure to Bevirimat

2010 ◽  
Vol 54 (6) ◽  
pp. 2345-2353 ◽  
Author(s):  
Nicolas A. Margot ◽  
Craig S. Gibbs ◽  
Michael D. Miller
Keyword(s):  
Recombinant Viruses ◽  
Gag Polyprotein ◽  
New Class ◽  
Major Mutation ◽  
Hiv Drugs ◽  
The Impact ◽  
First Time ◽  
Hiv 1

ABSTRACT Bevirimat (BVM) is the first of a new class of anti-HIV drugs with a novel mode of action known as maturation inhibitors. BVM inhibits the last cleavage of the Gag polyprotein by HIV-1 protease, leading to the accumulation of the p25 capsid-small peptide 1 (SP1) intermediate and resulting in noninfectious HIV-1 virions. Early clinical studies of BVM showed that over 50% of the patients treated with BVM did not respond to treatment. We investigated the impact of prior antiretroviral (ARV) treatment and/or natural genetic diversity on BVM susceptibility by conducting in vitro phenotypic analyses of viruses made from patient samples. We generated 31 recombinant viruses containing the entire gag and protease genes from 31 plasma samples from HIV-1-infected patients with (n = 21) or without (n = 10) prior ARV experience. We found that 58% of the patient isolates tested had a >10-fold reduced susceptibility to BVM, regardless of the patient's ARV experience or the level of isolate resistance to protease inhibitors. Analysis of mutants with site-directed mutations confirmed the role of the V370A SP1 polymorphism (SP1-V7A) in resistance to BVM. Furthermore, we demonstrated for the first time that a capsid polymorphism, V362I (CA protein-V230I), is also a major mutation conferring resistance to BVM. In contrast, none of the previously defined resistance-conferring mutations in Gag selected in vitro (H358Y, L363M, L363F, A364V, A366V, or A366T) were found to occur among the viruses that we analyzed. Our results should be helpful in the design of diagnostics for prediction of the potential benefit of BVM treatment in HIV-1-infected patients.

The balance between p53 isoforms modulates the efficiency of HIV-1 infection in macrophages

2021 ◽  
Author(s):  
Yann Breton ◽  
Corinne Barat ◽  
Michel J. Tremblay
Keyword(s):  
Virus Replication ◽  
Potential Role ◽  
Host Factors ◽  
Fine Tuning ◽  
Mrna Levels ◽  
Cellular Environment ◽  
P53 Isoforms ◽  
Antiviral Role ◽  
Hiv 1

Several host factors influence HIV-1 infection and replication. The p53-mediated antiviral role in monocytes-derived macrophages (MDMs) was previously highlighted. Indeed, an increase in p53 level results in a stronger restriction against HIV-1 early replication steps through SAMHD1 activity. In this study, we investigated the potential role of some p53 isoforms in HIV-1 infection. Transfection of isoform-specific siRNA induces distinctive effects on the virus life cycle. For example, in contrast to a siRNA targeting all isoforms, a knockdown of Δ133p53 transcripts reduces virus replication in MDMs that is correlated with a decrease in phosphorylated inactive SAMHD1. Combination of Δ133p53 knockdown and Nutlin-3, a pharmacological inhibitor of MDM2 that stabilizes p53, further reduces susceptibility of MDMs to HIV-1 infection, thus suggesting an inhibitory role of Δ133p53 towards p53 antiviral activity. In contrast, p53β knockdown in MDMs increases the viral production independently of SAMHD1. Moreover, experiments with a Nef-deficient virus show that this viral protein plays a protective role against the antiviral environment mediated by p53. Finally, HIV-1 infection affects the expression pattern of p53 isoforms by increasing p53β and p53γ mRNA levels while stabilizing the protein level of p53α and some isoforms from the p53β subclass. The balance between the various p53 isoforms is therefore an important factor in the overall susceptibility of macrophages to HIV-1 infection, fine-tuning the p53 response against HIV-1. This study brings a new understanding of the complex role of p53 in virus replication processes in myeloid cells. Importance As of today, HIV-1 is still considered as a global pandemic without a functional cure, partly because of the presence of stable viral reservoirs. Macrophages constitute one of these cell reservoirs, contributing to the viral persistence. Studies investigating the host factors involved in cell susceptibility to HIV-1 infection might lead to a better understanding of the reservoir formation and will eventually allow the development of an efficient cure. Our team previously showed the antiviral role of p53 in macrophages, which acts by compromising the early steps of HIV-1 replication. In this study, we demonstrate the involvement of p53 isoforms, which regulates p53 activity and define the cellular environment influencing viral replication. In addition, the results concerning the potential role of p53 in antiviral innate immunity could be transposed to other fields of virology and suggest that knowledge in oncology can be applied to HIV-1 research.

scholarly journals HDAC stimulates gene expression through BRD4 availability in response to IFN and in interferonopathies

2018 ◽  
Vol 215 (12) ◽  
pp. 3194-3212 ◽  
Author(s):  
Isabelle J. Marié ◽  
Hao-Ming Chang ◽  
David E. Levy
Keyword(s):  
Autoimmune Diseases ◽  
Histone Deacetylases ◽  
Elongation Factor ◽  
Positive Function ◽  
Transcriptional Elongation ◽  
Hdac Inhibition ◽  
Transcriptional Initiation ◽  
Inducible Promoters ◽  
The Common

In contrast to the common role of histone deacetylases (HDACs) for gene repression, HDAC activity provides a required positive function for IFN-stimulated gene (ISG) expression. Here, we show that HDAC1/2 as components of the Sin3A complex are required for ISG transcriptional elongation but not for recruitment of RNA polymerase or transcriptional initiation. Transcriptional arrest by HDAC inhibition coincides with failure to recruit the epigenetic reader Brd4 and elongation factor P-TEFb due to sequestration of Brd4 on hyperacetylated chromatin. Brd4 availability is regulated by an equilibrium cycle between opposed acetyltransferase and deacetylase activities that maintains a steady-state pool of free Brd4 available for recruitment to inducible promoters. An ISG expression signature is a hallmark of interferonopathies and other autoimmune diseases. Combined inhibition of HDAC1/2 and Brd4 resolved the aberrant ISG expression detected in cells derived from patients with two inherited interferonopathies, ISG15 and USP18 deficiencies, defining a novel therapeutic approach to ISG-associated autoimmune diseases.

scholarly journals The AFF4 scaffold binds human P-TEFb adjacent to HIV Tat

eLife ◽  
2013 ◽  
Vol 2 ◽  
Author(s):  
Ursula Schulze-Gahmen ◽  
Heather Upton ◽  
Andrew Birnberg ◽  
Katherine Bao ◽  
Seemay Chou ◽  
...  
Keyword(s):  
Rna Polymerase Ii ◽  
Elongation Factor ◽  
Regulatory Proteins ◽  
Tat Protein ◽  
Elongation Complex ◽  
Cyclin T1 ◽  
Subunit Interface ◽  
Hiv Tat ◽  
Gene Transcripts ◽  
Hiv 1

Human positive transcription elongation factor b (P-TEFb) phosphorylates RNA polymerase II and regulatory proteins to trigger elongation of many gene transcripts. The HIV-1 Tat protein selectively recruits P-TEFb as part of a super elongation complex (SEC) organized on a flexible AFF1 or AFF4 scaffold. To understand this specificity and determine if scaffold binding alters P-TEFb conformation, we determined the structure of a tripartite complex containing the recognition regions of P-TEFb and AFF4. AFF4 meanders over the surface of the P-TEFb cyclin T1 (CycT1) subunit but makes no stable contacts with the CDK9 kinase subunit. Interface mutations reduced CycT1 binding and AFF4-dependent transcription. AFF4 is positioned to make unexpected direct contacts with HIV Tat, and Tat enhances P-TEFb affinity for AFF4. These studies define the mechanism of scaffold recognition by P-TEFb and reveal an unanticipated intersubunit pocket on the AFF4 SEC that potentially represents a target for therapeutic intervention against HIV/AIDS.

scholarly journals Efficient Non-Epigenetic Activation of HIV Latency through the T-Cell Receptor Signalosome

Viruses ◽  
2020 ◽  
Vol 12 (8) ◽  
pp. 868
Author(s):  
Joseph Hokello ◽  
Adhikarimayum Lakhikumar Sharma ◽  
Mudit Tyagi
Keyword(s):  
T Cells ◽  
Transcription Factors ◽  
T Cell Receptor ◽  
Elongation Factor ◽  
Cell Receptor ◽  
Hiv Latency ◽  
Transcriptional Elongation ◽  
Nuclear Factor ◽  
Epigenetic Mechanisms ◽  
Hiv 1

Human immunodeficiency virus type-1 (HIV-1) can either undergo a lytic pathway to cause productive systemic infections or enter a latent state in which the integrated provirus remains transcriptionally silent for decades. The ability to latently infect T-cells enables HIV-1 to establish persistent infections in resting memory CD4+ T-lymphocytes which become reactivated following the disruption or cessation of intensive drug therapy. The maintenance of viral latency occurs through epigenetic and non-epigenetic mechanisms. Epigenetic mechanisms of HIV latency regulation involve the deacetylation and methylation of histone proteins within nucleosome 1 (nuc-1) at the viral long terminal repeats (LTR) such that the inhibition of histone deacetyltransferase and histone lysine methyltransferase activities, respectively, reactivates HIV from latency. Non-epigenetic mechanisms involve the nuclear restriction of critical cellular transcription factors such as nuclear factor-kappa beta (NF-κB) or nuclear factor of activated T-cells (NFAT) which activate transcription from the viral LTR, limiting the nuclear levels of the viral transcription transactivator protein Tat and its cellular co-factor positive transcription elongation factor b (P-TEFb), which together regulate HIV transcriptional elongation. In this article, we review how T-cell receptor (TCR) activation efficiently induces NF-κB, NFAT, and activator protein 1 (AP-1) transcription factors through multiple signal pathways and how these factors efficiently regulate HIV LTR transcription through the non-epigenetic mechanism. We further discuss how elongation factor P-TEFb, induced through an extracellular signal-regulated kinase (ERK)-dependent mechanism, regulates HIV transcriptional elongation before new Tat is synthesized and the role of AP-1 in the modulation of HIV transcriptional elongation through functional synergy with NF-κB. Furthermore, we discuss how TCR signaling induces critical post-translational modifications of the cyclin-dependent kinase 9 (CDK9) subunit of P-TEFb which enhances interactions between P-TEFb and the viral Tat protein and the resultant enhancement of HIV transcriptional elongation.

scholarly journals The Role of RNA Polymerase II Elongation Control in HIV-1 Gene Expression, Replication, and Latency

2011 ◽  
Vol 2011 ◽  
pp. 1-9 ◽  
Author(s):  
Kyle A. Nilson ◽  
David H. Price
Keyword(s):  
Rna Polymerase ◽  
Rna Polymerase Ii ◽  
Elongation Factor ◽  
Health Concern ◽  
Pol Ii ◽  
Positive Transcription Elongation Factor ◽  
Elongation Control ◽  
Hiv 1 ◽  
Latent Phase

HIV-1 usurps the RNA polymerase II elongation control machinery to regulate the expression of its genome during lytic and latent viral stages. After integration into the host genome, the HIV promoter within the long terminal repeat (LTR) is subject to potent downregulation in a postinitiation step of transcription. Once produced, the viral protein Tat commandeers the positive transcription elongation factor, P-TEFb, and brings it to the engaged RNA polymerase II (Pol II), leading to the production of viral proteins and genomic RNA. HIV can also enter a latent phase during which factors that regulate Pol II elongation may play a role in keeping the virus silent. HIV, the causative agent of AIDS, is a worldwide health concern. It is hoped that knowledge of the mechanisms regulating the expression of the HIV genome will lead to treatments and ultimately a cure.

scholarly journals Ubiquitylation of Cdk9 by Skp2 Facilitates Optimal Tat Transactivation

2005 ◽  
Vol 79 (17) ◽  
pp. 11135-11141 ◽  
Author(s):  
Matjaz Barboric ◽  
Fan Zhang ◽  
Mojca Besenicar ◽  
Ana Plemenitas ◽  
B. Matija Peterlin
Keyword(s):  
Rna Polymerase Ii ◽  
Elongation Factor ◽  
Transcriptional Elongation ◽  
Cyclin Dependent Kinase ◽  
Primary Mouse ◽  
Immunodeficiency Virus ◽  
F Box Protein ◽  
Hiv 1

ABSTRACT By recruiting the positive transcriptional elongation factor b (P-TEFb) to paused RNA polymerase II, the transactivator Tat stimulates transcriptional elongation of the human immunodeficiency virus type 1 (HIV-1) genome. We found that cyclin-dependent kinase 9 (Cdk9), the catalytic subunit of P-TEFb, is ubiquitylated in vivo. This ubiquitylation depended on the Skp1/Cul1/F-box protein E3 ubiquitin ligase Skp2. Likewise, Tat required Skp2 since its transactivation of the HIV-1 long terminal repeat decreased in primary mouse embryonic fibroblasts, which lacked Skp2. The ubiquitylation of Cdk9 by Skp2 facilitated the formation of the ternary complex between P-TEFb, Tat, and transactivation response element. Thus, our findings underscore the requirement of ubiquitylation for the coactivator function in regulating HIV-1 transcriptional elongation.

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