Heat Shock Protein 40 Is Necessary for Human Immunodeficiency Virus-1 Nef-mediated Enhancement of Viral Gene Expression and Replication

Protein Quality Control Systems and ER Stress as Key Players in SARS-CoV-2-Induced Neurodegeneration

The COVID-19 pandemic has brought to the forefront the intricate relationship between SARS-CoV-2 and its impact on neurological complications, including potential links to neurodegenerative processes, characterized by a dysfunction of the protein quality control systems and ER stress. This review article explores the role of protein quality control systems, such as the Unfolded Protein Response (UPR), the Endoplasmic Reticulum-Associated Degradation (ERAD), the Ubiquitin-Proteasome System (UPS), autophagy and the molecular chaperones, in SARS-CoV-2 infection. Our hypothesis suggests that SARS-CoV-2 produces ER stress and exploits the protein quality control systems, leading to a disruption in proteostasis that cannot be solved by the host cell. This disruption culminates in cell death and may represent a link between SARS-CoV-2 and neurodegeneration.

Plasma metabolomics by nuclear magnetic resonance reveals biomarkers and metabolic pathways associated with the control of HIV-1 infection/progression

How the human body reacts to the exposure of HIV-1 is an important research goal. Frequently, HIV exposure leads to infection, but some individuals show natural resistance to this infection; they are known as HIV-1-exposed but seronegative (HESN). Others, although infected but without antiretroviral therapy, control HIV-1 replication and progression to AIDS; they are named controllers, maintaining low viral levels and an adequate count of CD4⁺ T lymphocytes. Biological mechanisms explaining these phenomena are not precise. In this context, metabolomics emerges as a method to find metabolites in response to pathophysiological stimuli, which can help to establish mechanisms of natural resistance to HIV-1 infection and its progression. We conducted a cross-sectional study including 30 HESN, 14 HIV-1 progressors, 14 controllers and 30 healthy controls. Plasma samples (directly and deproteinized) were analyzed through Nuclear Magnetic Resonance (NMR) metabolomics to find biomarkers and altered metabolic pathways. The metabolic profile analysis of progressors, controllers and HESN demonstrated significant differences with healthy controls when a discriminant analysis (PLS-DA) was applied. In the discriminant models, 13 metabolites associated with HESN, 14 with progressors and 12 with controllers were identified, which presented statistically significant mean differences with healthy controls. In progressors, the metabolites were related to high energy expenditure (creatinine), mood disorders (tyrosine) and immune activation (lipoproteins), phenomena typical of the natural course of the infection. In controllers, they were related to an inflammation-modulating profile (glutamate and pyruvate) and a better adaptive immune system response (acetate) associated with resistance to progression. In the HESN group, with anti-inflammatory (lactate and phosphocholine) and virucidal (lactate) effects which constitute a protective profile in the sexual transmission of HIV. Concerning the significant metabolites of each group, we identified 24 genes involved in HIV-1 replication or virus proteins that were all altered in progressors but only partially in controllers and HESN. In summary, our results indicate that exposure to HIV-1 in HESN, as well as infection in progressors and controllers, affects the metabolism of individuals and that this affectation can be determined using NMR metabolomics.

DNAJB8 facilitates autophagic-lysosomal degradation of viral Vif protein and restricts HIV-1 virion infectivity by rescuing APOBEC3G expression in host cells

HSP40/DNAJ family of proteins is the most diverse chaperone family, comprising about 49 isoforms in humans. Several reports have demonstrated the functional role of a few of these isoforms in the pathogenesis of various viruses, including HIV-1. Our earlier study has shown that several isoforms of HSP40 get significantly modulated at the mRNA level during HIV-1 infection in T cells. To explore the biological role of these significantly modulated isoforms, we analyzed their effect on HIV-1 gene expression and virus production using knockdown and overexpression studies. Among these isoforms, DNAJA3, DNAJB1, DNAJB7, DNAJC4, DNAJC5B, DNAJC5G, DNAJC6, DNAJC22, and DNAJC30 seem to positively regulate virus replication, whereas DNAJB3, DNAJB6, DNAJB8, and DNAJC5 negatively regulate virus replication. Further investigation on the infectivity of the progeny virion demonstrated that only DNAJB8 negatively regulates the progeny virion infectivity. It was further identified that DNAJB8 protein is involved in the downregulation of Vif protein, required for the infectivity of HIV-1 virions. DNAJB8 seems to direct Vif protein for autophagic-lysosomal degradation, leading to rescue of the cellular restriction factor APOBEC3G from Vif-mediated proteasomal degradation, resulting in enhanced packaging of APOBEC3G in budding virions and release of less infective progeny virion particles. Finally, our results also indicate that during the early stage of HIV-1 infection, enhanced expression of DNAJB8 promotes the production of less infective progeny virions, but at the later stage or at the peak of infection, reduced expression of DNJAB8 protein allows the HIV-1 to replicate and produce more infective progeny virion particles.

Heat shock protein: A double-edged sword linking innate immunity and hepatitis B virus infection

Heat shock proteins (HSPs), which have a variety of functions, are one of the stress protein families. In recent years, They have been reported to play a dual role in hepatitis B virus (HBV) which as persistent infection which is associated with, cirrhosis and liver cancer. In this article, we have summarized the regulatory mechanisms between HSPs and viruses, especially HBV and associated diseases based on HSP biological functions of in response to viral infections. In view of their potential as broad-spectrum antiviral targets, we have also discuss current progress and challenges in drug development based on HSPs, as well as the potential applications of agents that have been evaluated clinically in HBV treatment.

DNAJA3 Interacts with PEDV S1 Protein and Inhibits Virus Replication by Affecting Virus Adsorption to Host Cells

Porcine epidemic diarrhea virus (PEDV) infection causes huge economic losses to the pig industry worldwide. DNAJA3, a member of the Hsp40 family proteins, is known to play an important role in the replication of several viruses. However, it remains unknown if it interacts with PEDV. We found that DNAJA3 interacted with PEDV S1, initially with yeast two-hybrid screening and later with Co-IP, GST pull-down, and confocal imaging. Further experiments showed the functional relationship between DNAJA3 and PEDV in the infected IPEC-J2 cells. DNAJA3 overexpression significantly inhibited PEDV replication while its knockdown had the opposite effect, suggesting that it is a negative regulator of PEDV replication. In addition, DNAJA3 expression could be downregulated by PEDV infection possibly as the viral strategy to evade the suppressive role of DNAJA3. By gene silencing and overexpression, we were able to show that DNAJA3 inhibited PEDV adsorption to IPEC-J2 cells but did not affect virus invasion. In conclusion, our study provides clear evidence that DNAJA3 mediates PEDV adsorption to host cells and plays an antiviral role in IPEC-J2 cells.

Direct observation of chaperone-modulated talin mechanics with single-molecule resolution

Talin as a critical focal adhesion mechanosensor exhibits force-dependent folding dynamics and concurrent interactions. Being a cytoplasmic protein, talin also might interact with several cytosolic chaperones; however, the roles of chaperones in talin mechanics remain elusive. To address this question, we investigated the force response of a mechanically stable talin domain with a set of well-known unfoldase (DnaJ, DnaK) and foldase (DnaKJE, DsbA) chaperones, using single-molecule magnetic tweezers. Our findings demonstrate that chaperones could affect adhesion proteins’ stability by changing their folding mechanics; while unfoldases reduce their unfolding force from ~11 pN to ~6 pN, foldase shifts it upto ~15 pN. Since talin is mechanically synced within 2 pN force ranges, these changes are significant in cellular conditions. Furthermore, we determined that chaperones directly reshape the energy landscape of talin: unfoldases decrease the unfolding barrier height from 26.8 to 21.7 k_BT, while foldases increase it to 33.5 k_BT. We reconciled our observations with eukaryotic Hsp70 and Hsp40 and observed their similar function of decreasing the talin unfolding barrier. Quantitative mapping of this chaperone-induced talin folding landscape directly illustrates that chaperones perturb the adhesion protein stability under physiological force, thereby, influencing their force-dependent interactions and adhesion dynamics.

Chakraborty et al. uses single-molecule magnetic tweezers to investigate the chaperone-modulated talin protein mechanics. The results showed that chaperones are involved in the regulation of talin folding/unfolding under mechanical force with some chaperones stabilizing talin and increasing the force, whereas others destabilize it and reduce the force.

Genome-wide comparative analysis of DNAJ genes and their co-expression patterns with HSP70s in aestivation of the sea cucumber Apostichopus japonicus

DNAJ proteins function as co-chaperones of HSP70 and play key roles in cell physiology to promote protein folding and degradation, especially under environmental stress. Based on our previous study on HSP70, a systematic study of DNAJ was performed in sea cucumber Apostichopus japonicus using the transcriptomic and genomic data, identifying 43 AjDNAJ genes, including six AjDNAJA genes, eight AjDNAJB genes, and 29 AjDNAJC genes. Slight expansion and conserved genomic structure were observed using the phylogenetic and syntenic analysis. Differential period-specific and tissue-specific expression patterns of AjDNAJs were observed between adult and juvenile individuals during aestivation. Strong tissue-specific expression correlations between AjDNAJ and AjHSP70 genes were found, indicating that the involvements of AjHSP70IVAs in the aestivation of sea cucumbers were regulated by AjDNAJs. Several key genes with significant expression correlations, such as AjDNAJB4L and AjHSP70IVAs, were suggested to function together under heat stress. Together, these findings provide early insight into the involvement of AjDNAJs in the aestivation and their roles as co-chaperones of AjHSP70s.

Diversity in heat shock protein families: functional implications in virus infection with a comprehensive insight of their role in the HIV-1 life cycle

Heat shock proteins (HSPs) are a group of cellular proteins that are induced during stress conditions such as heat stress, cold shock, UV irradiation and even pathogenic insult. They are classified into families based on molecular size like HSP27, 40, 70 and 90 etc, and many of them act as cellular chaperones that regulate protein folding and determine the fate of mis-folded or unfolded proteins. Studies have also shown multiple other functions of these proteins such as in cell signalling, transcription and immune response. Deregulation of these proteins leads to devastating consequences, such as cancer, Alzheimer's disease and other life threatening diseases suggesting their potential importance in life processes. HSPs exist in multiple isoforms, and their biochemical and functional characterization still remains a subject of active investigation. In case of viral infections, several HSP isoforms have been documented to play important roles with few showing pro-viral activity whereas others seem to have an anti-viral role. Earlier studies have demonstrated that HSP40 plays a pro-viral role whereas HSP70 inhibits HIV-1 replication; however, clear isoform-specific functional roles remain to be established. A detailed functional characterization of all the HSP isoforms will uncover their role in cellular homeostasis and also may highlight some of them as potential targets for therapeutic strategies against various viral infections. In this review, we have tried to comprehend the details about cellular HSPs and their isoforms, their role in cellular physiology and their isoform-specific functions in case of virus infection with a specific focus on HIV-1 biology.

Comparative analysis of differential gene expression of HSP40 and HSP70 family isoforms during heat stress and HIV-1 infection in T-cells

Heat shock proteins (HSPs) are a family of cellular proteins involved in a variety of biological functions including chaperone activity. HSPs are classified based on their molecular weight and each family has several isoforms in eukaryotes. HSP40 is the most diverse family acting as a co-chaperone for the highly conserved HSP70 family. Some of the isoforms are reported to be induced during heat stress. Few studies have also highlighted the diverse role of some isoforms in different stress conditions including viral infections. But till date, no study has comprehensively examined the expression profile of different HSP40 and 70 isoforms in either heat stress or HIV-1 infection, a virus that is responsible for the pandemic of AIDS. In the present study, we have compared the mRNA expression profile of HSP40 and HSP70 isoforms during heat stress and HIV-1 infection in a T-cell line and also validated the HIV-1 stress results in peripheral blood mononuclear cells. In case of HSP70, we observed that three isoforms (HSPA1A, HSPA1B, and HSPA6) are highly upregulated during heat stress, but these isoforms were found to be downregulated during the peak of HIV-1 infection. While in case of HSP40, we found that only DNAJA4, DNAJB1, and DNAJB4 showed significant upregulation during heat stress, whereas in HIV-1 infection, majority of the isoforms were induced significantly. Stress-dependent differential expression observed here indicates that different HSP40 and HSP70 isoforms may have specific roles during HIV-1 infection and thus could be important for future studies.

The Role of Molecular Chaperones in Virus Infection and Implications for Understanding and Treating COVID-19

The COVID-19 pandemic made imperative the search for means to end it, which requires a knowledge of the mechanisms underpinning the multiplication and spread of its cause, the coronavirus SARS-CoV-2. Many viruses use members of the hosts’ chaperoning system to infect the target cells, replicate, and spread, and here we present illustrative examples. Unfortunately, the role of chaperones in the SARS-CoV-2 cycle is still poorly understood. In this review, we examine the interactions of various coronaviruses during their infectious cycle with chaperones in search of information useful for future research on SARS-CoV-2. We also call attention to the possible role of molecular mimicry in the development of autoimmunity and its widespread pathogenic impact in COVID-19 patients. Viral proteins share highly antigenic epitopes with human chaperones, eliciting anti-viral antibodies that crossreact with the chaperones. Both, the critical functions of chaperones in the infectious cycle of viruses and the possible role of these molecules in COVID-19 autoimmune phenomena, make clear that molecular chaperones are promising candidates for the development of antiviral strategies. These could consist of inhibiting-blocking those chaperones that are necessary for the infectious viral cycle, or those that act as autoantigens in the autoimmune reactions causing generalized destructive effects on human tissues.

Redefining proteostasis transcription factors in organismal stress responses, development, metabolism, and health

Eukaryotic organisms have evolved complex and robust cellular stress response pathways to ensure maintenance of proteostasis and survival during fluctuating environmental conditions. Highly conserved stress response pathways can be triggered and coordinated at the cell-autonomous and cell-nonautonomous level by proteostasis transcription factors, including HSF1, SKN-1/NRF2, HIF1, and DAF-16/FOXO that combat proteotoxic stress caused by environmental challenges. While these transcription factors are often associated with a specific stress condition, they also direct “noncanonical” transcriptional programs that serve to integrate a multitude of physiological responses required for development, metabolism, and defense responses to pathogen infections. In this review, we outline the established function of these key proteostasis transcription factors at the cell-autonomous and cell-nonautonomous level and discuss a newly emerging stress responsive transcription factor, PQM-1, within the proteostasis network. We look beyond the canonical stress response roles of proteostasis transcription factors and highlight their function in integrating different physiological stimuli to maintain cytosolic organismal proteostasis.

Stress proteins: the biological functions in virus infection, present and challenges for target-based antiviral drug development

Stress proteins (SPs) including heat-shock proteins (HSPs), RNA chaperones, and ER associated stress proteins are molecular chaperones essential for cellular homeostasis. The major functions of HSPs include chaperoning misfolded or unfolded polypeptides, protecting cells from toxic stress, and presenting immune and inflammatory cytokines. Regarded as a double-edged sword, HSPs also cooperate with numerous viruses and cancer cells to promote their survival. RNA chaperones are a group of heterogeneous nuclear ribonucleoproteins (hnRNPs), which are essential factors for manipulating both the functions and metabolisms of pre-mRNAs/hnRNAs transcribed by RNA polymerase II. hnRNPs involve in a large number of cellular processes, including chromatin remodelling, transcription regulation, RNP assembly and stabilization, RNA export, virus replication, histone-like nucleoid structuring, and even intracellular immunity. Dysregulation of stress proteins is associated with many human diseases including human cancer, cardiovascular diseases, neurodegenerative diseases (e.g., Parkinson’s diseases, Alzheimer disease), stroke and infectious diseases. In this review, we summarized the biologic function of stress proteins, and current progress on their mechanisms related to virus reproduction and diseases caused by virus infections. As SPs also attract a great interest as potential antiviral targets (e.g., COVID-19), we also discuss the present progress and challenges in this area of HSP-based drug development, as well as with compounds already under clinical evaluation.

HSF1 Activation Can Restrict HIV Replication

Host protein folding stress responses can play important roles in RNA virus replication and evolution. Prior work suggested a complicated interplay between the cytosolic proteostasis stress response, controlled by the transcriptional master regulator heat shock factor 1 (HSF1), and human immunodeficiency virus-1 (HIV-1). We sought to uncouple HSF1 transcription factor activity from cytotoxic proteostasis stress and thereby better elucidate the proposed role(s) of HSF1 in the HIV-1 lifecycle. To achieve this objective, we used chemical genetic, stress-independent control of HSF1 activity to establish whether and how HSF1 influences HIV-1 replication. Stress-independent HSF1 induction decreased both the total quantity and infectivity of HIV-1 virions. Moreover, HIV-1 was unable to escape HSF1-mediated restriction over the course of several serial passages. These results clarify the interplay between the host's heat shock response and HIV-1 infection and motivate continued investigation of chaperones as potential antiviral therapeutic targets.

Proteostasis in Viral Infection: Unfolding the Complex Virus-Chaperone Interplay

Viruses are obligate intracellular parasites that rely on their hosts for protein synthesis, genome replication, and viral particle production. As such, they have evolved mechanisms to divert host resources, including molecular chaperones, facilitate folding and assembly of viral proteins, stabilize complex structures under constant mutational pressure, and modulate signaling pathways to dampen antiviral responses and prevent premature host death. Biogenesis of viral proteins often presents unique challenges to the proteostasis network, as it requires the rapid and orchestrated production of high levels of a limited number of multifunctional, multidomain, and aggregation-prone proteins. To overcome such challenges, viruses interact with the folding machinery not only as clients but also as regulators of chaperone expression, function, and subcellular localization. In this review, we summarize the main types of interactions between viral proteins and chaperones during infection, examine evolutionary aspects of this relationship, and discuss the potential of using chaperone inhibitors as broad-spectrum antivirals.

Hsp40 Protein DNAJB6 Interacts with Viral NS3 and Inhibits the Replication of the Japanese Encephalitis Virus

The Japanese encephalitis virus (JEV) is a mosquito-borne flavivirus prevalent in east and southeast Asia, the Western Pacific, and northern Australia. Since viruses are obligatory intracellular pathogens, the dynamic processes of viral entry, replication, and assembly are dependent on numerous host-pathogen interactions. Efforts to identify JEV-interacting host factors are ongoing because their identification and characterization remain incomplete. Three enzymatic activities of flavivirus non-structural protein 3 (NS3), including serine protease, RNA helicase, and triphosphatase, play major roles in the flaviviruses lifecycle. To identify cellular factors that interact with NS3, we screened a human brain cDNA library using a yeast two-hybrid assay, and identified eight proteins that putatively interact with NS3: COPS5, FBLN5, PPP2CB, CRBN, DNAJB6, UBE2N, ZNF350, and GPR137B. We demonstrated that the DnaJ heat shock protein family (Hsp40) member B6 (DNAJB6) colocalizes and interacts with NS3, and has a negative regulatory function in JEV replication. We also show that loss of DNAJB6 function results in significantly increased viral replication, but does not affect viral binding or internalization. Moreover, the time-course of DNAJB6 disruption during JEV infection varies in a viral load-dependent manner, suggesting that JEV targets this host chaperone protein for viral benefit. Deciphering the modes of NS3-interacting host proteins functions in virion production will shed light on JEV pathogenic mechanisms and may also reveal new avenues for antiviral therapeutics.

Discovery of 2-isoxazol-3-yl-acetamide analogues as heat shock protein 90 (HSP90) inhibitors with significant anti-HIV activity

The recent burst of explorations on heat shock protein 90 (HSP90) in virus research supports its emergence as a promising target to overcome the drawbacks of current antiviral therapeutic regimen. In continuation of our efforts towards the discovery of novel anti-retroviral molecules, we designed, synthesized fifteen novels 2-isoxazol-3-yl-acetamide based compounds (2a-o) followed by analysis of their anti-HIV activity and cytotoxicity studies. 2a-b, 2e, 2j, and 2l-m were found to be active with inhibitory potentials >80% at their highest non-cytotoxic concentration (HNC). Further characterization of anti-HIV activity of these molecules suggests that 2l has ∼3.5 fold better therapeutic index than AUY922, the second generation HSP90 inhibitor. The anti-HIV activity of 2l is a cell type, virus isolate and viral load independent phenomena. Interestingly, 2l does not significantly modulate viral enzymes like Reverse Transcriptase (RT), Integrase (IN) and Protease (PR) as compared to their known inhibitors in a cell free in vitro assay system at its HNC. Further, 2l mediated inhibition of HSP90 attenuates HIV-1 LTR driven gene expression. Taken together, structural rationale, modeling studies and characterization of biological activities suggest that this novel scaffold can attenuate HIV-1 replication significantly within the host and thus opens a new horizon to develop novel anti-HIV therapeutic candidates.

Heat shock proteins in infection

Heat shock proteins (HSPs) are constitutively expressed under physiological conditions in most organisms but their expression can significantly enhance in response to four types of stimuli including physical (e.g., radiation or heat shock), chemical and microbial (e.g., pathogenic bacteria, viruses, parasites and fungi) stimuli, and also dietary. These proteins were identified for their role in protecting cells from high temperature and other forms of stress. HSPs control physiological activities or virulence through interaction with various regulators of cellular signaling pathways. Several roles were determined for HSPs in the immune system including intracellular roles (e.g., antigen presentation and expression of innate receptors) as well as extracellular roles (e.g., tumor immunosurveillance and autoimmunity). It was observed that exogenously administered HSPs induced various immune responses in immunotherapy of cancer, infectious diseases, and autoimmunity. Moreover, virus interaction with HSPs as molecular chaperones showed important roles in regulating viral infections including cell entry and nuclear import, viral replication and gene expression, folding/assembly of viral protein, apoptosis regulation, and host immunity. Viruses could regulate host HSPs at different levels such as transcription, translation, post-translational modification and cellular localization. In this review, we attempt to overview the roles of HSPs in a variety of infectious diseases.

Cellular DNAJA3, a Novel VP1-Interacting Protein, Inhibits Foot-and-Mouth Disease Virus Replication by Inducing Lysosomal Degradation of VP1 and Attenuating Its Antagonistic Role in the Beta Interferon Signaling Pathway

DnaJ heat shock protein family (Hsp40) member A3 (DNAJA3) plays an important role in viral infections. However, the role of DNAJA3 in replication of foot-and-mouth-disease virus (FMDV) remains unknown. In this study, DNAJA3, a novel binding partner of VP1, was identified using yeast two-hybrid screening. The DNAJA3-VP1 interaction was further confirmed by coimmunoprecipitation and colocalization in FMDV-infected cells. The J domain of DNAJA3 (amino acids 1 to 168) and the lysine at position 208 (K208) of VP1 were shown to be critical for the DNAJA3-VP1 interaction. Overexpression of DNAJA3 dramatically dampened FMDV replication, whereas loss of function of DNAJA3 elicited opposing effects against FMDV replication. Mechanistical study demonstrated that K208 of VP1 was critical for reducing virus titer caused by DNAJA3 using K208A mutant virus. DNAJA3 induced lysosomal degradation of VP1 by interacting with LC3 to enhance the activation of lysosomal pathway. Meanwhile, we discovered that VP1 suppressed the beta interferon (IFN-β) signaling pathway by inhibiting the phosphorylation, dimerization, and nuclear translocation of IRF3. This inhibitory effect was considerably boosted in DNAJA3-knockout cells. In contrast, overexpression of DNAJA3 markedly attenuated VP1-mediated suppression on the IFN-β signaling pathway. Poly(I⋅C)-induced phosphorylation of IRF3 was also decreased in DNAJA3-knockout cells compared to that in the DNAJA3-WT cells. In conclusion, our study described a novel role for DNAJA3 in the host's antiviral response by inducing the lysosomal degradation of VP1 and attenuating the VP1-induced suppressive effect on the IFN-β signaling pathway.IMPORTANCE This study pioneeringly determined the antiviral role of DNAJA3 in FMDV. DNAJA3 was found to interact with FMDV VP1 and trigger its degradation via the lysosomal pathway. In addition, this study is also the first to clarify the mechanism by which VP1 suppressed IFN-β signaling pathway by inhibiting the phosphorylation, dimerization, and nuclear translocation of IRF3. Moreover, DNAJA3 significantly abrogated VP1-induced inhibitive effect on the IFN-β signaling pathway. These data suggested that DNAJA3 plays an important antiviral role against FMDV by both degrading VP1 and restoring of IFN-β signaling pathway.

Interference of DNAJB6/MRJ Isoform Switch by Morpholino Inhibits Replication of HIV-1 and RSV

The molecular chaperon MRJ (DNAJB6) exhibits two splice isoforms that have different roles in human viral infection, but the regulatory mechanism of MRJ isoform expression is yet unclear. In this study, we show that reduction of the polyadenylation factor CstF64 was correlated with the increase of the MRJ large isoform (MRJ-L) in human macrophages and elucidate the mechanism underlying CstF64-modulated MRJ isoform expression. Moreover, we exploited an antisense strategy targeting MRJ-L for virus replication. A morpholino oligonucleotide complementary to the 5′ splice site of MRJ intron 8 downregulated MRJ-L expression and suppressed the replication of not only HIV-1 but also respiratory syncytial virus (RSV). We demonstrated that downregulation of the MRJ-L level reduced HIV-1 replication as well as the subgenomic mRNA and viral production of RSV. The present findings that two human health-threatening viruses take advantage of MRJ-L for infection suggest MRJ-L as a potential target for broad-spectrum antiviral strategy.

Roles of heat shock factor 1 beyond the heat shock response

Various stress factors leading to protein damage induce the activation of an evolutionarily conserved cell protective mechanism, the heat shock response (HSR), to maintain protein homeostasis in virtually all eukaryotic cells. Heat shock factor 1 (HSF1) plays a central role in the HSR. HSF1 was initially known as a transcription factor that upregulates genes encoding heat shock proteins (HSPs), also called molecular chaperones, which assist in refolding or degrading injured intracellular proteins. However, recent accumulating evidence indicates multiple additional functions for HSF1 beyond the activation of HSPs. Here, we present a nearly comprehensive list of non-HSP-related target genes of HSF1 identified so far. Through controlling these targets, HSF1 acts in diverse stress-induced cellular processes and molecular mechanisms, including the endoplasmic reticulum unfolded protein response and ubiquitin-proteasome system, multidrug resistance, autophagy, apoptosis, immune response, cell growth arrest, differentiation underlying developmental diapause, chromatin remodelling, cancer development, and ageing. Hence, HSF1 emerges as a major orchestrator of cellular stress response pathways.

Multiple Inhibitory Factors Act in the Late Phase of HIV-1 Replication: a Systematic Review of the Literature

The use of lentiviral vectors for therapeutic purposes has shown promising results in clinical trials. The ability to produce a clinical-grade vector at high yields remains a critical issue. One possible obstacle could be cellular factors known to inhibit human immunodeficiency virus (HIV). To date, five HIV restriction factors have been identified, although it is likely that more factors are involved in the complex HIV-cell interaction. Inhibitory factors that have an adverse effect but do not abolish virus production are much less well described. Therefore, a gap exists in the knowledge of inhibitory factors acting late in the HIV life cycle (from transcription to infection of a new cell), which are relevant to the lentiviral vector production process. The objective was to review the HIV literature to identify cellular factors previously implicated as inhibitors of the late stages of lentivirus production. A search for publications was conducted on MEDLINE via the PubMed interface, using the keyword sequence "HIV restriction factor" or "HIV restriction" or "inhibit HIV" or "repress HIV" or "restrict HIV" or "suppress HIV" or "block HIV," with a publication date up to 31 December 2016. Cited papers from the identified records were investigated, and additional database searches were performed. A total of 260 candidate inhibitory factors were identified. These factors have been identified in the literature as having a negative impact on HIV replication. This study identified hundreds of candidate inhibitory factors for which the impact of modulating their expression in lentiviral vector production could be beneficial.

Heat Shock Protein 90 Facilitates Latent HIV Reactivation through Maintaining the Function of Positive Transcriptional Elongation Factor b (p-TEFb) under Proteasome Inhibition

The persistence of HIV in resting memory CD4⁺ T cells at a latent state is considered as the major barrier on the path to achieve a cure for HIV. Proteasome inhibitors (PIs) were previously reported as latency reversing agents (LRAs) but the mechanism underlying this function is yet unclear. Here we demonstrate that PIs reactivate latent HIV ex vivo without global T cell activation, and may facilitate host innate immune responses. Mechanistically, latent HIV reactivation induced by PIs is mediated by heat shock factor 1 (HSF1) via the recruitment of the heat shock protein (HSP) 90-positive transcriptional elongation factor b (p-TEFb) complex. Specifically, HSP90 downstream HSF1 gives positive feedback to the reactivation process through binding to cyclin-dependent kinase 9 (CDK9) and preventing it from undergoing degradation by the proteasome. Overall, these findings suggest proteasome inhibitors as potential latency reversing agents. In addition, HSF1/HSP90 involved in HIV transcription elongation, may serve as therapeutic targets in HIV eradication.

Shrimp miRNAs regulate innate immune response against white spot syndrome virus infection

MicroRNAs are short noncoding RNAs of RNA interference pathways that regulate gene expression through partial complementary base-pairing to target mRNAs. In this study, miRNAs that are expressed in white spot syndrome virus (WSSV)-infected Penaeus monodon, were identified using next generation sequencing. Forty-six miRNA homologs were identified from WSSV-infected shrimp hemocyte. Stem-loop real-time RT-PCR analysis showed that 11 out of 16 selected miRNAs were differentially expressed upon WSSV infection. Of those, pmo-miR-315 and pmo-miR-750 were highly responsive miRNAs. miRNA target prediction revealed that the miRNAs were targeted at 5'UTR, ORF, and 3'UTR of several immune-related genes such as genes encoding antimicrobial peptides, signaling transduction proteins, heat shock proteins, oxidative stress proteins, proteinases or proteinase inhibitors, proteins in blood clotting system, apoptosis-related proteins, proteins in prophenoloxidase system, pattern recognition proteins and other immune molecules. The highly conserved miRNA homolog, pmo-bantam, was characterized for its function in shrimp. The pmo-bantam was predicted to target the 3'UTR of Kunitz-type serine protease inhibitor (KuSPI). Binding of pmo-bantam to the target sequence of KuSPI gene was analyzed by luciferase reporter assay. Correlation of pmo-bantam and KuSPI expression was observed in lymphoid organ of WSSV-infected shrimp. These results implied that miRNAs might play roles as immune gene regulators in shrimp antiviral response.

Human Heat shock protein 40 (Hsp40/DnaJB1) promotes influenza A virus replication by assisting nuclear import of viral ribonucleoproteins

A unique feature of influenza A virus (IAV) life cycle is replication of the viral genome in the host cell nucleus. The nuclear import of IAV genome is an indispensable step in establishing virus infection. IAV nucleoprotein (NP) is known to mediate the nuclear import of viral genome via its nuclear localization signals. Here, we demonstrate that cellular heat shock protein 40 (Hsp40/DnaJB1) facilitates the nuclear import of incoming IAV viral ribonucleoproteins (vRNPs) and is important for efficient IAV replication. Hsp40 was found to interact with NP component of IAV RNPs during early stages of infection. This interaction is mediated by the J domain of Hsp40 and N-terminal region of NP. Drug or RNAi mediated inhibition of Hsp40 resulted in reduced nuclear import of IAV RNPs, diminished viral polymerase function and attenuates overall viral replication. Hsp40 was also found to be required for efficient association between NP and importin alpha, which is crucial for IAV RNP nuclear translocation. These studies demonstrate an important role for cellular chaperone Hsp40/DnaJB1 in influenza A virus life cycle by assisting nuclear trafficking of viral ribonucleoproteins.

HSP70 binding protein 1 (HspBP1) suppresses HIV-1 replication by inhibiting NF-κB mediated activation of viral gene expression

HIV-1 efficiently hijacks host cellular machinery and exploits a plethora of host–viral interactions for its successful survival. Identifying host factors that affect susceptibility or resistance to HIV-1 may offer a promising therapeutic strategy against HIV-1. Previously, we have reported that heat shock proteins, HSP40 and HSP70 reciprocally regulate HIV-1 gene-expression and replication. In the present study, we have identified HSP70 binding protein 1 (HspBP1) as a host-intrinsic inhibitor of HIV-1. HspBP1 level was found to be significantly down modulated during HIV-1 infection and virus production inversely co-related with HspBP1 expression. Our results further demonstrate that HspBP1 inhibits HIV-1 long terminal repeat (LTR) promoter activity. Gel shift and chromatin immunoprecipitation assays revealed that HspBP1 was recruited on HIV-1 LTR at NF-κB enhancer region (κB sites). The binding of HspBP1 to κB sites obliterates the binding of NF-κB hetero-dimer (p50/p65) to the same region, leading to repression in NF-κB mediated activation of LTR-driven gene-expression. HspBP1 also plays an inhibitory role in the reactivation of latently infected cells, corroborating its repressive effect on NF-κB pathway. Thus, our results clearly show that HspBP1 acts as an endogenous negative regulator of HIV-1 gene-expression and replication by suppressing NF-κB-mediated activation of viral transcription.

Evolutionary distance of amino acid sequence orthologs across macaque subspecies: identifying candidate genes for SIV resistance in Chinese rhesus macaques

We use the Reciprocal Smallest Distance (RSD) algorithm to identify amino acid sequence orthologs in the Chinese and Indian rhesus macaque draft sequences and estimate the evolutionary distance between such orthologs. We then use GOanna to map gene function annotations and human gene identifiers to the rhesus macaque amino acid sequences. We conclude methodologically by cross-tabulating a list of amino acid orthologs with large divergence scores with a list of genes known to be involved in SIV or HIV pathogenesis. We find that many of the amino acid sequences with large evolutionary divergence scores, as calculated by the RSD algorithm, have been shown to be related to HIV pathogenesis in previous laboratory studies. Four of the strongest candidate genes for SIVmac resistance in Chinese rhesus macaques identified in this study are CDK9, CXCL12, TRIM21, and TRIM32. Additionally, ANKRD30A, CTSZ, GORASP2, GTF2H1, IL13RA1, MUC16, NMDAR1, Notch1, NT5M, PDCD5, RAD50, and TM9SF2 were identified as possible candidates, among others. We failed to find many laboratory experiments contrasting the effects of Indian and Chinese orthologs at these sites on SIVmac pathogenesis, but future comparative studies might hold fertile ground for research into the biological mechanisms underlying innate resistance to SIVmac in Chinese rhesus macaques.

Tat predominantly associates with host promoter elements in HIV-1-infected T-cells - regulatory basis of transcriptional repression of c-Rel

HIV-1 Tat is a multifunctional regulatory protein that, in addition to its primary function of transactivating viral transcription, also tends to modulate cellular gene expression, for which the molecular mechanism remains to be clarified. We have reported earlier nuclear factor kappa B (NFκB) enhancer binding activity of Tat and proposed this DNA binding activity as a possible molecular basis for Tat-mediated regulation of cellular gene expression in infected cells. In the present study, we analyzed the genome-wide occupancy of Tat protein on host cell chromatin in HIV-1-infected T-cells to investigate a potential role of Tat on cellular gene expression. The results obtained identify a spectrum of binding sites of Tat protein on the chromatin and reveal that Tat is also recruited on a number of cellular gene promoters in HIV-1-infected T-cells, indicating its possible involvement in the regulation of gene expression of such cellular genes. Tat was identified as a repressor of one such validated gene, c-Rel, because it downregulates the expression of c-Rel in both Tat expressing and HIV-1-infected T-cells. The results also show that Tat downregulates c-Rel promoter activity by interacting with specific NFκB sites on the c-Rel promoter, thus providing a molecular basis of Tat-mediated regulation of cellular gene expression. Thus, in the present study, we have not only identified recruitment sites of Tat on the chromatin in HIV-1-infected T-cells, but also report for the first time that c-Rel is downregulated in HIV-1-infected cells specifically by interaction of Tat with NFκB binding sites on the promoter.

Inhibition of HSP70 reduces porcine reproductive and respiratory syndrome virus replication in vitro

Background

Successful viral infection requires the involvement of host cellular factors in their life cycle. Heat shock protein 70 (HSP70) can be recruited by numerous viruses to promote the folding, maturation, or assembly of viral proteins. We have previously shown that HSP70 is significantly elevated in porcine reproductive and respiratory syndrome virus (PRRSV)-infected lungs, suggesting HSP70 may play a potential role during PRRSV infection. In this study, we tried to investigate the role of HSP70 during PRRSV infection.

Results

In this study, we observed that PRRSV infection induced the expression of HSP70. The down-regulation of HSP70 using quercetin, a HSPs synthesis inhibitor, or small interfering RNAs (siRNA) reduced the viral protein level and viral production. Notably, these inhibitory effects on PRRSV infection could be attenuated by heat shock treatment. In addition, HSP70 was found to colocalize with the viral double-stranded RNA (dsRNA) and knockdown of HSP70 decreased the dsRNA levels, suggesting HSP70 is involved in the formation of viral replication and transcription complex (RTC) and thus affects the viral replication.

Conclusions

Our study revealed that HSP70 is an essential host factor required for the replication of PRRSV. The inhibition of HSP70 significantly reduced PRRSV replication, which may be applied as an effective antiviral strategy.

Novel role of HSP40/DNAJ in the regulation of HIV-1 replication

OBJECTIVES

DNAJ/HSP40 is an evolutionarily conserved family of proteins bearing various functions. Historically, it has been emphasized that HSP40/DNAJ family proteins play a positive role in infection of various viruses. We identified DNAJ/HSP40B6 as a potential negative regulator of HIV-1 replication in our genetic screens. In this study, we investigated the functional interactions between HIV-1 and HSP40 family members.

DESIGN

We took genetic and comparative virology approaches to expand the primary observation.

METHODS

Multiple HSP40/DNAJ proteins were tested for their ability to inhibit replication of adenovirus, herpes simplex virus type 1, HIV-1, and vaccinia virus. The mechanism of inhibition was investigated by using HSP40/DNAJ mutants and measuring the efficiencies of each viral replication steps.

RESULTS

HSP40A1, B1, B6, and C5, but not C3, were found to be able to limit HIV-1 production. This effect was specific to HIV-1 for such effects were not detected in adenovirus, herpes simplex virus type 1, and vaccinia virus. Genetic analyses suggested that the conserved DNAJ domain was responsible for the inhibition of HIV-1 production through which HSP40 regulates HSP70 ATPase activity. Interestingly, HSP40s lowered the levels of steady-state viral messenger RNA. This was not attributed to the inhibition of Tat/long terminal repeat-driven transcription but the downregulation of Rev expression.

CONCLUSIONS

This is the first report providing evidence that HSP70-HSP40 complex confers an innate resistance specific to HIV-1. For their interferon-inducible nature, HSP40 family members should account for the anti-HIV-1 function of interferon.

A computational study identifies HIV progression-related genes using mRMR and shortest path tracing

Since statistical relationships between HIV load and CD4+ T cell loss have been demonstrated to be weak, searching for host factors contributing to the pathogenesis of HIV infection becomes a key point for both understanding the disease pathology and developing treatments. We applied Maximum Relevance Minimum Redundancy (mRMR) algorithm to a set of microarray data generated from the CD4+ T cells of viremic non-progressors (VNPs) and rapid progressors (RPs) to identify host factors associated with the different responses to HIV infection. Using mRMR algorithm, 147 gene had been identified. Furthermore, we constructed a weighted molecular interaction network with the existing protein-protein interaction data from STRING database and identified 1331 genes on the shortest-paths among the genes identified with mRMR. Functional analysis shows that the functions relating to apoptosis play important roles during the pathogenesis of HIV infection. These results bring new insights of understanding HIV progression.

Anti-HIV-1 activity, protease inhibition and safety profile of extracts prepared from Rhus parviflora

Background

In the present study, extracts prepared from the leaves of Rhus parviflora Roxb. (Anacardiaceae) were evaluated for their anti-HIV activity, which have been traditionally used for the treatment of neurological disorders such as anxiety, insomnia and epilepsy.

Methods

Aqueous and 50% ethanolic extracts prepared from leaves of the plant were tested for their cytotoxicity and anti-HIV property using reporter gene based assays as well as human peripheral blood lymphocytes (PBLs). Further these extracts were evaluated for their ability to inhibit HIV-1 reverse transcriptase (RT) and protease activity. Safety profile of the extracts was determined on viability of Lactobacillus sp., secretion of pro-inflammatory cytokines by vaginal keratinocytes and transepithelial resistance.

Results

Both aqueous (IC₅₀ = 15 μg/ml) and 50% ethanolic (IC₅₀ = 26 μg/ml) extracts prepared from leaves of R. parviflora showed anti-HIV activity in TZM-bl cells wherein the virus was treated with the extracts prior to infection. Further, both the extracts also inhibited virus load in HIV infected CEM-GFP cells and human PBLs. The anti-HIV activity is mediated through inhibition of HIV-1 protease activity. Both the extracts did not disturb the integrity of monolayer formed by intestinal epithelial Caco-2 cells. The extracts when tested up to 100 μg/ml did not significantly reduce the viability of L. plantarum, L. fermentum, L. rhamnosus and L. casei. The extracts (100 μg/ml) did not reveal any cytotoxic effect on vaginal keratinocytes (Vk2/E6E7). Levels of pro-inflammatory cytokines secreted by Vk2/E6E7 cells treated with both the plant extracts were within the non-inflammatory range.

Conclusions

The studies reported herein showed in vitro anti-HIV activity and preliminary safety profile of the extracts prepared from the leaves of R. parviflora.

Identification of cellular proteins required for replication of human immunodeficiency virus type 1

Cellular proteins are essential for human immunodeficiency virus type 1 (HIV-1) replication and may serve as viable new targets for treating infection. Using gene trap insertional mutagenesis, a high-throughput approach based on random inactivation of cellular genes, candidate genes were found that limit virus replication when mutated. Disrupted genes (N=87) conferring resistance to lytic infection with several viruses were queried for an affect on HIV-1 replication by utilizing small interfering RNA (siRNA) screens in TZM-bl cells. Several genes regulating diverse pathways were found to be required for HIV-1 replication, including DHX8, DNAJA1, GTF2E1, GTF2E2, HAP1, KALRN, UBA3, UBE2E3, and VMP1. Candidate genes were independently tested in primary human macrophages, toxicity assays, and/or Tat-dependent β-galactosidase reporter assays. Bioinformatics analyses indicated that several host factors present in this study participate in canonical pathways and functional processes implicated in prior genome-wide studies. However, the genes presented in this study did not share identity with those found previously. Novel antiviral targets identified in this study should open new avenues for mechanistic investigation.

Novel inhibitors of heat shock protein Hsp70-mediated luciferase refolding that bind to DnaJ

Inhibitors of both heat shock proteins Hsp90 and Hsp70 have been identified in assays measuring luciferase refolding containing rabbit reticulocyte lysate or purified chaperone components. Here, we report the discovery of a series of phenoxy-N-arylacetamides that disrupt Hsp70-mediated luciferase refolding by binding to DnaJ, the bacterial homolog of human Hsp40. Inhibitor characterization experiments demonstrated negative cooperativity with respect to DnaJ and luciferase concentration, but varying the concentration of ATP had no effect on potency. Thermal shift analysis suggested a direct interaction with DnaJ, but not with Hsp70. These compounds may be useful tools for studying DnaJ/Hsp40 in various cellular processes.

DnaJ homolog Hdj2 facilitates Japanese encephalitis virus replication

Background

Japanese encephalitis virus (JEV) is a member of the mosquito-borne Flaviviridae family of viruses that causes human encephalitis. Upon infection of a new host, replication of viral RNA involves not only the viral RNA-dependent RNA polymerase (RdRp), but also host proteins. Host factors involved in JEV replication are not well characterized.

Results

We identified Hdj2, a heat-shock protein 40 (Hsp40)/DnaJ homolog, from a mouse brain cDNA library interacting with JEV nonstructural protein 5 (NS5) encoding viral RdRp using yeast two-hybrid system. Specific interaction of Hdj2 with NS5 was confirmed by coimmunoprecipitation and colocalization in JEV-infected cells. Overexpression of Hdj2 in JEV-infected cells led to an increase of RNA synthesis, and the virus titer was elevated approximately 4.5- to 10-fold. Knocking down of Hdj2 by siRNA reduced the virus production significantly.

Conclusions

We conclude that Hdj2 directly associates with JEV NS5 and facilitates viral replication. This study is the first to demonstrate Hdj2 involved in JEV replication, providing insight into a potential therapeutic target and cell-based vaccine development of JEV infection.

Human immunodeficiency virus-1 Nef suppresses Hsp70-mediated Tat activation

The human immunodeficiency virus type 1 (HIV-1) long terminal repeat (LTR) contains binding sites for several host transcription factors that contribute to HIV-1 gene expression. Although previous reports have indicated that HIV-1 Nef positively or negatively regulates HIV-1 gene expression, the precise molecular mechanisms by which this occurs remain largely unknown. In this study, we report that Nef suppressed LTR-driven transcription only in the presence of HIV-1 Tat, which was localized to the cytoplasm and degraded by the proteasome. However, the depletion of Hsp70 was found to reduce the suppressive effect of Nef on HIV-1 gene expression. These results suggest that Nef suppresses Hsp70-mediated HIV-1 Tat activation.

Reciprocal regulation of human immunodeficiency virus-1 gene expression and replication by heat shock proteins 40 and 70

Cellular heat shock proteins (Hsps) are induced upon heat shock, UV irradiation and microbial or viral infection. They are also known to be involved in apoptosis and immune response in addition to their chaperone function. Although some literature exists regarding the role of Hsps in human immunodeficiency virus (HIV)-1 infection, a clear understanding of their role remains elusive. Previously, we have shown that Hsp40, a co-chaperone of Hsp70, interacts with HIV-1 negative regulatory factor (Nef) and is required for Nef-mediated increase in viral gene expression and replication. We now show that Hsp70 is also present in the Nef-Hsp40 complex reported earlier. Furthermore, Hsp70 inhibits viral gene expression and replication; however, Hsp40 can rescue this down regulation of viral gene expression induced by Hsp70. We also show that HIV-1 viral protein R is required for this inhibitory effect of Hsp70 on viral replication. Our data further show that Hsp40 is consistently up regulated in HIV-1 infection, whereas Hsp70 is down regulated after initial up regulation favoring viral replication. Finally, Hsp70 expression inhibits the phosphorylation of cyclin-dependent kinase 9 required for high-affinity binding of HIV-1 transactivator of transcription-positive transcription elongation factor b complex to transactivation response RNA, whereas Hsp40 seems to induce it. Thus, Hsp40 and Hsp70, both closely associated in their chaperone function, seem to act contrary to each other in regulating viral gene expression. It seems that Hsp70 favors the host by inhibiting viral replication, whereas Hsp40 works in favor of the virus by inducing its replication. Thus, differential expression of Hsp40 and Hsp70 reciprocally regulates viral gene expression and replication in HIV-1 infection.

Theiler's murine encephalomyelitis virus infection induces a redistribution of heat shock proteins 70 and 90 in BHK-21 cells, and is inhibited by novobiocin and geldanamycin

Theiler's murine encephalomyelitis virus (TMEV) is a positive-sense RNA virus belonging to the Cardiovirus genus in the family Picornaviridae. In addition to other host cellular factors and pathways, picornaviruses utilise heat shock proteins (Hsps) to facilitate their propagation in cells. This study investigated the localisation of Hsps 70 and 90 in TMEV-infected BHK-21 cells by indirect immunofluorescence and confocal microscopy. The effect of Hsp90 inhibitors novobiocin (Nov) and geldanamycin (GA) on the development of cytopathic effect (CPE) induced by infection was also examined. Hsp90 staining was uniformly distributed in the cytoplasm of uninfected cells but was found concentrated in the perinuclear region during late infection where it overlapped with the signal for non-structural protein 2C within the viral replication complex. Hsp70 redistributed into the vicinity of the viral replication complex during late infection, but its distribution did not overlap with that of 2C. Inhibition of Hsp90 by GA and Nov had a negative effect on virus growth over a 48-h period as indicated by no observable CPE in treated compared to untreated cells. 2C was detected by Western analysis of GA-treated infected cell lysates at doses between 0.01 and 0.125 μM, suggesting that processing of viral precursors was not affected in the presence of this drug. In contrast, 2C was absent in cell lysates of Nov-treated cells at doses above 10 μM, although CPE was evident 48 hpi. This is the first study describing the dynamic behaviour of Hsps 70 and 90 in TMEV-infected cells and to identify Hsp90 as an important host factor in the life cycle of this virus.

Influenza A virus nucleoprotein exploits Hsp40 to inhibit PKR activation

Background

Double-stranded RNA dependent protein kinase (PKR) is a key regulator of the anti-viral innate immune response in mammalian cells. PKR activity is regulated by a 58 kilo Dalton cellular inhibitor (P58^IPK), which is present in inactive state as a complex with Hsp40 under normal conditions. In case of influenza A virus (IAV) infection, P58^IPK is known to dissociate from Hsp40 and inhibit PKR activation. However the influenza virus component responsible for PKR inhibition through P58^IPK activation was hitherto unknown.

Principal Findings

Human heat shock 40 protein (Hsp40) was identified as an interacting partner of Influenza A virus nucleoprotein (IAV NP) using a yeast two-hybrid screen. This interaction was confirmed by co-immunoprecipitation studies from mammalian cells transfected with IAV NP expressing plasmid. Further, the IAV NP-Hsp40 interaction was validated in mammalian cells infected with various seasonal and pandemic strains of influenza viruses. Cellular localization studies showed that NP and Hsp40 co-localize primarily in the nucleus. During IAV infection in mammalian cells, expression of NP coincided with the dissociation of P58^IPK from Hsp40 and decrease PKR phosphorylation. We observed that, plasmid based expression of NP in mammalian cells leads to decrease in PKR phosphorylation. Furthermore, inhibition of NP expression during influenza virus replication led to PKR activation and concomitant increase in eIF2α phosphorylation. Inhibition of NP expression also led to reduced IRF3 phosphorylation, enhanced IFN β production and concomitant reduction of virus replication. Taken together our data suggest that NP is the viral factor responsible for P58^IPK activation and subsequent inhibition of PKR-mediated host response during IAV infection.

Significance

Our findings demonstrate a novel role of IAV NP in inhibiting PKR-mediated anti-viral host response and help us understand P58^IPK mediated inhibition of PKR activity during IAV infection.

Cyclin K inhibits HIV-1 gene expression and replication by interfering with cyclin-dependent kinase 9 (CDK9)-cyclin T1 interaction in Nef-dependent manner

Human immunodeficiency virus-1 (HIV-1) exploits a number of host cellular factors for successful survival and propagation. The viral protein Nef plays an important role in HIV-1 pathogenesis by interacting with various cellular proteins. In the present work, we identified Cyclin K (CycK) as a novel Nef-interacting protein, and for the first time, we showed that CycK inhibits HIV-1 gene expression and replication in a Nef-dependent manner. The positive elongation factor b complex comprising cyclin-dependent kinase 9 (CDK9) and Cyclin T1 is a critical cellular complex required for viral gene expression and replication. Enhanced expression of CycK in the presence of Nef induced CycK-CDK9 binding, which prevented CDK9-Cyclin T1 complex formation and nuclear translocation of CDK9, resulting in inhibition of HIV-1 long terminal repeat-driven gene expression. Furthermore, this effect of CycK was not observed with Nef-deleted virus, indicating the importance of Nef in this phenomenon. Finally, silencing of CycK in HIV-1-infected cells resulted in increased translocation of CDK9 into the nucleus, leading to increased viral gene expression and replication. These data also suggest that endogenous CycK might act as an inhibitory factor for HIV-1 gene expression and replication in T-cells. Thus, our results clearly demonstrate that CycK utilizes HIV-1 Nef protein to displace CycT1 from the positive elongation factor b complex, resulting in inhibition of HIV-1 gene expression and replication.

Active participation of cellular chaperone Hsp90 in regulating the function of rotavirus nonstructural protein 3 (NSP3)

Heat shock protein 90 (Hsp90) has been reported to positively regulate rotavirus replication by modulating virus induced PI3K/Akt and NFκB activation. Here, we report the active association of Hsp90 in the folding and stabilization of rotavirus nonstructural protein 3 (NSP3). In pCD-NSP3-transfected cells, treatment with Hsp90 inhibitor (17-N,N-dimethylethylenediamine-geldanamycin (17DMAG)) resulted in the proteasomal degradation of NSP3. Sequence analysis and deletion mutations revealed that the region spanning amino acids 225-258 within the C-terminal eIF4G-binding domain of NSP3 is a putative Hsp90 binding region. Co-immunoprecipitation and mammalian two-hybrid experiments revealed direct interaction of the C-terminal 12-kDa domain of Hsp90 (C90) with residues 225-258 of NSP3. NSP3-Hsp90 interaction is important for the formation of functionally active mature NSP3, because full-length NSP3 in the presence of the Hsp90 inhibitor or NSP3 lacking the amino acid 225-258 region did not show NSP3 dimers following in vitro coupled transcription-translation followed by chase. Disruption of residues 225-258 within NSP3 also resulted in poor RNA binding and eIF4G binding activity. In addition, inhibition of Hsp90 by 17DMAG resulted in reduced nuclear translocation of poly(A)-binding protein and translation of viral proteins. These results highlight the crucial role of Hsp90 chaperone in the regulation of assembly and functionality of a viral protein during the virus replication and propagation in host cells.

Cellular heat shock factor 1 positively regulates human immunodeficiency virus-1 gene expression and replication by two distinct pathways

Human immunodeficiency virus-1 (HIV-1) infection leads to changes in cellular gene expression, which in turn tend to modulate viral gene expression and replication. Cellular heat shock proteins (HSPs) are induced upon heat shock, UV irradiation and microbial or viral infections. We have reported earlier Nef-dependent induction of HSP40 leading to increased HIV-1 gene expression; however, the mechanism of induction remained to be elucidated. As expression of HSPs is regulated by heat shock factors (HSFs), we have now studied the role of HSF1 not only in Nef-dependent HSP40 induction but also in HIV-1 gene expression. Our results show that HSF1 is also induced during HIV-1 infection and it positively regulates HIV-1 gene expression by two distinct pathways. First, along with Nef it activates HSP40 promoter which in turn leads to increased HIV-1 gene expression. Second, HSF1 directly interacts with newly identified HSF1 binding sequence on HIV-1 LTR promoter and induces viral gene expression and replication. Thus, the present work not only identifies a molecular basis for HSF1-mediated enhancement of viral replication but also provides another example of how HIV-1 uses host cell machinery for its successful replication in the host.

Anti-HIV activity of Indian medicinal plants

Acquired immunodeficiency syndrome patients face great socio-economic difficulties in obtaining treatment. There is an urgent need for new, safe, and cheap anti-HIV agents. Traditional medicinal plants are a valuable source of novel anti-HIV agents and may offer alternatives to expensive medicines in future. Various medicinal plants or plant-derived natural products have shown strong anti-HIV activity and are under various stages of clinical development in different parts of the world. The present study was directed towards assessment of anti-HIV activity of various extracts prepared from Indian medicinal plants. The plants were chosen on the basis of similarity of chemical constituents with reported anti-HIV compounds or on the basis of their traditional usage as immunomodulators. Different extracts were prepared by Soxhlet extraction and liquid-liquid partitioning. Ninety-two extracts were prepared from 23 plants. Anti-HIV activity was measured in a human CD4+ T-cell line, CEM-GFP cells infected with HIV-1NL4.3. Nine extracts of 8 different plants significantly reduced viral production in CEM-GFP cells infected with HIV-1NL4.3. Aegle marmelos, Argemone mexicana, Asparagus racemosus, Coleus forskohlii, and Rubia cordifolia demonstrated promising anti-HIV potential and were investigated for their active principles.

Hyperthermia potentiates oncolytic herpes viral killing of pancreatic cancer through a heat shock protein pathway

BACKGROUND

Oncolytic herpes simplex virus-1 (HSV-1) is designed to specifically infect, replicate in, and lyse cancer cells. This study investigates a novel therapeutic regimen, combining the effects of NV1066 (a recombinant HSV-1) and hyperthermia in the treatment of pancreatic cancer.

METHODS

NV1066 is an attenuated HSV-1 that replicates in cells resistant to apoptosis. Heat shock protein 72 (Hsp72) is a member of a family of proteins that is upregulated after hyperthermic insult, lending cellular protection by inhibiting apoptosis. In these experiments, we test the hypothesis that increased Hsp72 expression in response to hyperthermia enhances anti-apoptotic mechanisms, thereby increasing viral replication and tumor cell kill. Hs 700T pancreatic cancer cells were treated with hyperthermia alone (42 degrees C), NV1066 alone, and combination therapy. Cell survival and viral growth were measured. The effect of siRNA-directed Hsp72 knockdown was also measured.

RESULTS

Combining hyperthermia and viral treatment produced a synergistic effect on cell kill. Viral growth increased greater than 6-fold in the presence of hyperthermia (P < .05). Hyperthermia alone showed minimal cytotoxic activity against Hs 700T cells, while NV1066 infection resulted in approximately 50% cell kill. The combination of hyperthermia and viral infection significantly increased cell kill to approximately 80% (P < .01). Hsp72 knockdown attenuated this synergistic effect.

CONCLUSION

Hyperthermia enhances NV1066 replication, thereby potentiating the viral oncolytic response against pancreatic cancer cells. This finding has potential clinical application in the use of heated perfusion or permissive hyperthermia for delivery of oncolytic viral therapies.

Global genomics and proteomics approaches to identify host factors as targets to induce resistance against Tomato bushy stunt virus

The success of RNA viruses as pathogens of plants, animals, and humans depends on their ability to reprogram the host cell metabolism to support the viral infection cycle and to suppress host defense mechanisms. Plus-strand (+)RNA viruses have limited coding potential necessitating that they co-opt an unknown number of host factors to facilitate their replication in host cells. Global genomics and proteomics approaches performed with Tomato bushy stunt virus (TBSV) and yeast (Saccharomyces cerevisiae) as a model host have led to the identification of 250 host factors affecting TBSV RNA replication and recombination or bound to the viral replicase, replication proteins, or the viral RNA. The roles of a dozen host factors involved in various steps of the replication process have been validated in yeast as well as a plant host. Altogether, the large number of host factors identified and the great variety of cellular functions performed by these factors indicate the existence of a truly complex interaction between TBSV and the host cell. This review summarizes the advantages of using a simple plant virus and yeast as a model host to advance our understanding of virus–host interactions at the molecular and cellular levels. The knowledge of host factors gained can potentially be used to inhibit virus replication via gene silencing, expression of dominant negative mutants, or design of specific chemical inhibitors leading to novel specific or broad-range resistance and antiviral tools against (+)RNA plant viruses.