An Interaction with PARP-1 and Inhibition of Parylation Contribute to Attenuation of DNA Damage Signaling by the Adenovirus E4orf4 Protein

The adenoviral E4orf4 protein: A multifunctional protein serving as a guide for treating cancer, a multifactorial disease

Viruses exploit several cellular pathways to support their replication, and many of these virus-targeted pathways are also important for cancer growth. Consequently, studying virus-host interactions offers valuable insights into tumorigenesis and can suggest the development of novel anti-cancer therapies, with oncolytic viruses being one well-known example. The adenovirus E4orf4 protein, which disrupts several host regulatory pathways to facilitate viral infection, also functions as a potent anti-cancer agent when expressed independently. E4orf4 can selectively kill a wide range of cancer cell lines while sparing non-cancerous cells. Moreover, it effectively eliminated cancer in an in vivo Drosophila model without causing significant harm to normal tissues. In this study we provide evidence that an E4orf4-mimicking drug cocktail, comprising sublethal doses of four FDA-approved drugs targeting the pathways disrupted by E4orf4, significantly enhanced cancer cell death in many cancer cell types compared with individual drugs or less inclusive drug combinations. The quadruple drug cocktail was not toxic in non-cancerous cells. These findings provide a proof-of-principle for the potential application of virus-host interaction studies to design an effective E4orf4-based cancer therapy. Further investigation of E4orf4 interactions with the host cell will likely improve this E4orf4-based therapy by adding drugs that disrupt additional pathways. Crucially, the E4orf4-based approach offers a strategic advantage by avoiding the time-consuming development of novel drugs. Instead, it leverages existing drugs, including those that might be too toxic for use as monotherapies, by employing them at sublethal concentrations in combination. Thus, it provides a feasible and efficient method for advancing cancer therapy.

Identification of porcine PARP11 as a restricted factor for pseudorabies virus

Introduction

PRV infection in swine can cause devastating disease and pose a potential threat to humans. Advancing the interplay between PRV and host is essential to elucidate the pathogenic mechanism of PRV and identify novel anti-PRV targets.

Methods

PARP11-KO PK-15 cells were firstly constructed by CRISPR/Cas9 technology. Next, the effect of PARP11-KO on PRV infection was determined by RT-qPCR, TCID50 assay, RNA-seq, and western blot.

Results and discussion

In this study, we identified PARP11 as a host factor that can significantly affect PRV infection. Inhibition of PARP11 and knockout of PARP11 can significantly promoted PRV infection. Subsequently, we further found that PARP11 knockout upregulated the transcription of NXF1 and CRM1, resulting in enhanced transcription of viral genes. Furthermore, we also found that PARP11 knockout could activate the autophagy pathway and suppress the mTOR pathway during PRV infection. These findings could provide insight into the mechanism in which PARP11 participated during PRV infection and offer a potential target to develop anti-PRV therapies.

Identification of the Potential Role of the E4orf4 Protein in Adenovirus A, B, C, and D Groups in Cancer Therapy: Computational Approaches

The human adenovirus (HADV) early region 4 open reading frame 4 (E4orf4) protein plays a regulatory role in promoting viral infection by interacting with various cellular proteins. E4orf4 can induce death in cancer cells. One of the death pathways that is induced by this protein is related to the formation of membrane blebbing following the phosphorylation of tyrosine amino acids. The activation of this pathway requires the interaction of E4orf4 with Src family kinases (SFKs). The modulation mechanism of Src-dependent signaling via E4orf4 is not yet fully understood. However, evidence suggests that a physical association between the Src kinase domain and the arginine-rich motif of E4orf4 is crucial. Physically connecting E4orf4 to Src kinase leads to the deregulation of the Src-related signaling pathway, thereby inducing cytoplasmic death. In this study, we mapped the E4orf4 interaction site in Src to investigate the interaction between E4orf4 and Src in detail. We also compared the binding strength of E4orf4 proteins from different HADV groups. To this end, we performed bioinformatics structural analysis of the Src kinase domain and E4orf4 to identify E4orf4 interaction sites. The group with the lowest binding energy was predicted to be the most likely candidate for the highest cytoplasmic death in tumor cells based on the energy of the E4orf4-Src complex in various HADV groups. These results show that HADV-A and HADV-C have minimal binding energies to the E4orf4-Src complex, while the dissociation constant (Kd) of HADV-A was less than that of HADV-C. According to the obtained results, E4orf4 of the HADV-A group is more effective at triggering cytoplasmic death based on its most robust interaction with the Src kinase domain.

Metabolic Activation of PARP as a SARS-CoV-2 Therapeutic Target-Is It a Bait for the Virus or the Best Deal We Could Ever Make with the Virus? Is AMBICA the Potential Cure?

The COVID-19 pandemic has had a great impact on global health and is an economic burden. Even with vaccines and anti-viral medications we are still scrambling to get a balance. In this perspective, we have shed light upon an extremely feasible approach by which we can control the SARS-CoV-2 infection and the associated complications, bringing some solace to this ongoing turmoil. We are providing some insights regarding an ideal agent which could prevent SARS-CoV-2 multiplication. If we could identify an agent which is an activator of metabolism and is also bioactive, we could prevent corona activation (AMBICA). Some naturally occurring lipid molecules best fit this identity as an agent which has the capacity to replenish our host cells, specifically immune cells, with ATP. It could also act as a source for providing a substrate for host cell PARP family members for MARylation and PARylation processes, leading to manipulation of the viral macro domain function, resulting in curbing the virulence and propagation of SARS-CoV-2. Identification of the right lipid molecule or combination of lipid molecules will fulfill the criteria. This perspective has focused on a unique angle of host-pathogen interaction and will open up a new dimension in treating COVID-19 infection.

Role of PARP-1 in Human Cytomegalovirus Infection and Functional Partners Encoded by This Virus

Human cytomegalovirus (HCMV) is a ubiquitous pathogen that threats the majority of the world's population. Poly (ADP-ribose) polymerase 1 (PARP-1) and protein poly (ADP-ribosyl)ation (PARylation) regulates manifold cellular functions. The role of PARP-1 and protein PARylation in HCMV infection is still unknown. In the present study, we found that the pharmacological and genetic inhibition of PARP-1 attenuated HCMV replication, and PARG inhibition favors HCMV replication. PARP-1 and its enzymatic activity were required for efficient HCMV replication. HCMV infection triggered the activation of PARP-1 and induced the translocation of PARP-1 from nucleus to cytoplasm. PARG was upregulated in HCMV-infected cells and this upregulation was independent of viral DNA replication. Moreover, we found that HCMV UL76, a true late protein of HCMV, inhibited the overactivation of PARP-1 through direct binding to the BRCT domain of PARP-1. In addition, UL76 also physically interacted with poly (ADP-ribose) (PAR) polymers through the RG/RGG motifs of UL76 which mediates its recruitment to DNA damage sites. Finally, PARP-1 inhibition or depletion potentiated HCMV-triggered induction of type I interferons. Our results uncovered the critical role of PARP-1 and PARP-1-mediated protein PARylation in HCMV replication.

NAD+ Degrading Enzymes, Evidence for Roles During Infection

Declines in cellular nicotinamide adenine dinucleotide (NAD) contribute to metabolic dysfunction, increase susceptibility to disease, and occur as a result of pathogenic infection. The enzymatic cleavage of NAD⁺ transfers ADP-ribose (ADPr) to substrate proteins generating mono-ADP-ribose (MAR), poly-ADP-ribose (PAR) or O-acetyl-ADP-ribose (OAADPr). These important post-translational modifications have roles in both immune response activation and the advancement of infection. In particular, emergent data show viral infection stimulates activation of poly (ADP-ribose) polymerase (PARP) mediated NAD⁺ depletion and stimulates hydrolysis of existing ADP-ribosylation modifications. These studies are important for us to better understand the value of NAD⁺ maintenance upon the biology of infection. This review focuses specifically upon the NAD⁺ utilising enzymes, discusses existing knowledge surrounding their roles in infection, their NAD⁺ depletion capability and their influence within pathogenic infection.

The Antiviral Activities of Poly-ADP-Ribose Polymerases

The poly-adenosine diphosphate (ADP)-ribose polymerases (PARPs) are responsible for ADP-ribosylation, a reversible post-translational modification involved in many cellular processes including DNA damage repair, chromatin remodeling, regulation of translation and cell death. In addition to these physiological functions, recent studies have highlighted the role of PARPs in host defenses against viruses, either by direct antiviral activity, targeting certain steps of virus replication cycle, or indirect antiviral activity, via modulation of the innate immune response. This review focuses on the antiviral activity of PARPs, as well as strategies developed by viruses to escape their action.

The roles of PARP-1 and XPD and their potential interplay in repairing bupivacaine-induced neuron oxidative DNA damage

Bupivacaine has been widely used in clinical Anesthesia, but its neurotoxicity has been frequently reported, implicating cellular oxidative DNA damage as the major underlying mechanism. However, the mechanism underlying bupivacaine-induced oxidative DNA damage is unknown. We, thus, exposed SH-SY5Y cells to 1.5mM bupivacaine to induce neurotoxicity. Then, iTRAQ proteomic analysis was used to explore the repair of neuronal oxidative DNA damage. By analyzing the STRING version 11.0 database, the bioinformatics relationship between key repair enzymes was tracked. Subsequently, immunofluorescence co-localization and immunoprecipitation were used to investigate the interaction between key repair enzymes. The iTRAQ showed that Poly [ADP-ribose] polymerase 1 (PARP-1) from the base excision repair pathway participated closely in the repair of oxidative DNA damage induced by bupivacaine, and inhibition of PARP-1 expression significantly aggravated bupivacaine-induced DNA damage and apoptosis. Interestingly, this study showed that there were interactions and co-expression between PARP-1 and XPD (xeroderma pigmentosum D), another key protein of the nucleic acid excision repair pathway. After inhibiting XPD, PARP-1 expression was significantly reduced. However, simultaneous inhibition of both XPD and PARP-1 did not further increase DNA damage. It is concluded that PARP-1 may repair bupivacaine-induced oxidative DNA damage through XPD-mediated interactions.

En Guard! The Interactions between Adenoviruses and the DNA Damage Response

Virus–host cell interactions include several skirmishes between the virus and its host, and the DNA damage response (DDR) network is one of their important battlegrounds. Although some aspects of the DDR are exploited by adenovirus (Ad) to improve virus replication, especially at the early phase of infection, a large body of evidence demonstrates that Ad devotes many of its proteins, including E1B-55K, E4orf3, E4orf4, E4orf6, and core protein VII, and utilizes varied mechanisms to inhibit the DDR. These findings indicate that the DDR would strongly restrict Ad replication if allowed to function efficiently. Various Ad serotypes inactivate DNA damage sensors, including the Mre11-Rad50-Nbs1 (MRN) complex, DNA-dependent protein kinase (DNA-PK), and Poly (ADP-ribose) polymerase 1 (PARP-1). As a result, these viruses inhibit signaling via DDR transducers, such as the ataxia-telangiectasia mutated (ATM) and ATM- and Rad3-related (ATR) kinases, to downstream effectors. The different Ad serotypes utilize both shared and distinct mechanisms to inhibit various branches of the DDR. The aim of this review is to understand the interactions between Ad proteins and the DDR and to appreciate how these interactions contribute to viral replication.

NAD-linked mechanisms of gene de-repression and a novel role for CtBP in persistent adenovirus infection of lymphocytes

BACKGROUND

Adenovirus (AdV) infection is ubiquitous in the human population and causes acute infection in the respiratory and gastrointestinal tracts. In addition to lytic infections in epithelial cells, AdV can persist in a latent form in mucosal lymphocytes, and nearly 80% of children contain viral DNA in the lymphocytes of their tonsils and adenoids. Reactivation of latent AdV is thought to be the source of deadly viremia in pediatric transplant patients. Adenovirus latency and reactivation in lymphocytes is not well studied, though immune cell activation has been reported to promote productive infection from latency. Lymphocyte activation induces global changes in cellular gene expression along with robust changes in metabolic state. The ratio of free cytosolic NAD+/NADH can impact gene expression via modulation of transcriptional repressor complexes. The NAD-dependent transcriptional co-repressor C-terminal Binding Protein (CtBP) was discovered 25 years ago due to its high affinity binding to AdV E1A proteins, however, the role of this interaction in the viral life cycle remains unclear.

METHODS

The dynamics of persistently- and lytically-infected cells are evaluated. RT-qPCR is used to evaluate AdV gene expression following lymphocyte activation, treatment with nicotinamide, or disruption of CtBP-E1A binding.

RESULTS

PMA and ionomycin stimulation shifts the NAD+/NADH ratio in lymphocytic cell lines and upregulates viral gene expression. Direct modulation of NAD+/NADH by nicotinamide treatment also upregulates early and late viral transcripts in persistently-infected cells. We found differential expression of the NAD-dependent CtBP protein homologs between lymphocytes and epithelial cells, and inhibition of CtBP complexes upregulates AdV E1A expression in T lymphocyte cell lines but not in lytically-infected epithelial cells.

CONCLUSIONS

Our data provide novel insight into factors that can regulate AdV infections in activated human lymphocytes and reveal that modulation of cellular NAD+/NADH can de-repress adenovirus gene expression in persistently-infected lymphocytes. In contrast, disrupting the NAD-dependent CtBP repressor complex interaction with PxDLS-containing binding partners paradoxically alters AdV gene expression. Our findings also indicate that CtBP activities on viral gene expression may be distinct from those occurring upon metabolic alterations in cellular NAD+/NADH ratios or those occurring after lymphocyte activation.