Epstein-Barr virus miR-BHRF1-3 targets the BZLF1 3'UTR and regulates the lytic cycle

Sequence Analysis of microRNAs Encoded by Simian Lymphocryptoviruses

Lymphocryptoviruses (LCVs) are ubiquitous gamma-herpesviruses that establish life-long infections in both humans and non-human primates (NHPs). In immunocompromised hosts, LCV infections are commonly associated with B cell disorders and malignancies such as lymphoma. In this study, we evaluated simian LCV-encoded small microRNAs (miRNAs) present in lymphoblastoid cell lines (LCLs) derived from a Mauritian cynomolgus macaque (Macaca fascicularis) with cyLCV-associated post-transplant lymphoproliferative disease (PTLD) as well as the viral miRNAs expressed in a baboon (Papio hamadryas) LCL that harbors CeHV12. Via sequence comparisons, we further predicted viral miRNAs encoded by LCVs that infect two additional NHP species: stump-tailed macaques (Macaca arctoides) and bonobos (Pan paniscus). Together, these species represent two arms of the primate phylogeny: Hominoids (Pan) and Old-World monkeys (Macaca, Papio). Through our analysis, we defined sequences for >95 viral miRNAs encoded by these four NHP LCVs. Our study provides the most comprehensive annotation of NHP LCV miRNAs to date, yielding a resource for developing sequence-specific reagents to detect these molecules. Importantly, we further demonstrate that cyLCV miRNAs can be detected in circulation in vivo and have biomarker potential for LCV-related PTLD.

Identifying the key regulators orchestrating Epstein-Barr virus reactivation

Epstein-Barr virus (EBV) infects more than 90% of the human population worldwide and establishes lifelong infection in hosts by switching between latent and lytic infection. EBV latency can be reactivated under appropriate conditions, leading to expression of the viral lytic genes and production of infectious progeny viruses. EBV reactivation involves crosstalk between various factors and signaling pathways, and the subsequent complicated virus-host interplays determine whether EBV continues to propagate. However, the detailed mechanisms underlying these processes remain unclear. In this review, we summarize the critical factors regulating EBV reactivation and the associated mechanisms. This encompasses the transcription and post-transcriptional regulation of immediate-early (IE) genes, the functions of viral factors on viral DNA replication and progeny virus production, the mechanisms through which viral proteins disrupt and inhibit the host's innate immune response, and the host factors that modulate EBV reactivation. Finally, we explore the potential applications of novel technologies in studying EBV reactivation, providing novel insights into the investigation of mechanisms governing EBV reactivation and the development of anti-EBV therapeutic strategies.

Epstein-Barr Virus and gastric carcinoma pathogenesis with emphasis on underlying epigenetic mechanisms

Gastric cancer (GC) remains one of the top causes of cancer-related mortality around the world. The pathogenesis of GC is attributed to lifestyle, family history, genetic mutations, epigenetic alterations, as well as infectious agents such as Epstein-Barr Virus (EBV). EBV, a ubiquitous human gamma herpes virus, with latent asymptomatic infection in more than 95% of the world's population, is able to infect through the oral epithelium. EBV is described as the first virus found in human neoplastic, when it was detected in Burkitt lymphoma tumor biopsy. Nowadays this virus is considered to be involved in various human malignancies such as GC. Despite comprehensive efforts and immense studies, the main underlying mechanism is not well described as there are crucial contradictions regarding the presence of this virus and the prognosis of the disease. Immunological alterations, genetic mutations, and epigenetic modifications are among the most important criteria presented in EBV- associated gastric cancer (EBVaGC), leading to its consideration as a separate subtype with unique clinical, histological, biochemical, and genetic characteristics. The current study aimed to review the association between EBV and GC with an emphasis on the role of epigenetic modifications in the suppression or progression of carcinogenesis. To put all findings in a nutshell, several genes and chromatin mutations, promoter hypermethylation and subsequent silencing of related genes, and histone modifications and aberrant micro RNAs (miRNAs) expression were considered as the major altered mechanisms in the pathogenesis of EBVaGC, most of which able to be suggested as therapeutic targets. However, the current knowledge appeared to be imperfect, hence further studies are encouraged.

Functional Targets for Epstein-Barr Virus BART MicroRNAs in B Cell Lymphomas

MicroRNAs are key post-transcriptional regulators of gene expression and their dysregulation is often linked to cancer. Epstein-Barr virus encodes 22 BamHI A Rightward Transcript (BART) miRNAs, which are expressed in nearly all EBV-associated cancers and implicated in viral pathogenesis. To investigate biological targets for BART miRNAs in B cell lymphomas, we performed a meta-analysis of publicly available Ago-CLIP datasets from EBV-positive Burkitt lymphomas (BLs), primary effusion lymphomas (PELs), AIDS-associated diffuse large B cell lymphomas (DLBCLs), and lymphoblastoid cell lines (LCLs). Our analysis focused on comparing targets of EBV BART miRNAs across the different types of transformed B cells. Using reporter assays, we then experimentally validated over 50 functional interactions between BART miRNAs and cellular protein-coding transcripts involved in activities such as B cell differentiation (PRDM1, IRF4, and MYC), cell cycle regulation (UHMK1, CDKN1A, MDM2, and NPAT), apoptosis (MCL1), signaling and intracellular trafficking (GAB1, SOS1, MAPK1, RAB11A, CAV1, and RANBP9), and tumor suppression (CCDC6). Moreover, ectopic BART miRNA expression in several EBV-negative BL cells induced transcriptional changes that may influence molecular signatures of EBV-associated BLs. Collectively, our findings reveal novel, functional interactions for BART miRNAs in lymphomas and provide insights into their roles in these B cell cancers.

From virus to cancer: Epstein-Barr virus miRNA connection in Burkitt's lymphoma

In Burkitt's lymphoma (BL), Epstein-Barr virus-encoded microRNAs (EBV miRNAs) are emerging as crucial regulatory agents that impact cellular and viral gene regulation. This review investigates the multifaceted functions of EBV miRNAs in the pathogenesis of Burkitt lymphoma. EBV miRNAs regulate several cellular processes that are essential for BL development, such as apoptosis, immune evasion, and cellular proliferation. These small, non-coding RNAs target both viral and host mRNAs, finely adjusting the cellular environment to favor oncogenesis. Prominent miRNAs, such as BART (BamHI-A rightward transcript) and BHRF1 (BamHI fragment H rightward open reading frame 1), are emphasized for their roles in tumor growth and immune regulation. For example, BART miRNAs prevent apoptosis by suppressing pro-apoptotic proteins, whereas BHRF1 miRNAs promote viral latency and immunological evasion. Understanding the intricate connections among EBV miRNAs and their targets illuminates BL pathogenesis and suggests novel treatment approaches. Targeting EBV miRNAs or their specific pathways offers a feasible option for developing innovative therapies that aim to disrupt the carcinogenic processes initiated by these viral components. future studies should focus on precisely mapping miRNA‒target networks and developing miRNA-based diagnostic and therapeutic tools. This comprehensive article highlights the importance of EBV miRNAs in Burkitt lymphoma, indicating their potential as biomarkers and targets for innovative treatment strategies.

Duck plague virus-encoded microRNA dev-miR-D28-3p inhibits viral replication via targeting UL27

Herpesviruses-encoded microRNAs (miRNAs) have been discovered to be essential regulators in viral life cycle, participating in viral replication, latent or lytic infection, and immunological escape. However, the roles of miRNAs encoded by duck plague virus (DPV) are still unknown. Dev-miR-D28-3p is a miRNA uniquely encoded by DPV CHv strain. The aim of this study was to explore the effect of dev-miR-D28-3p on DPV replication and explore the potential mechanisms involved. Our findings demonstrated that transfection of dev-miR-D28-3p mimic into duck embryo fibroblasts (DEFs) effectively suppressed viral copies, viral titers and viral protein expressions during DPV infection, while the results above were reversed after transfection with dev-miR-D28-3p inhibitor. Subsequently, we further discovered that dev-miR-D28-3p specifically bound to DPV-encoded UL27 and inhibited its expression, suggesting that UL27 was the target gene of dev-miR-D28-3p. Finally, we investigated the role of UL27 in DPV replication and found the overexpression of UL27 increased viral copies, viral titers, and viral protein expressions; whereas the opposite results appear when knockdown of UL27. Our findings illustrated a novel mechanism that DPV regulated itself replication via dev-miR-D28-3p, paving the way for exploring the role of DPV-encoded miRNAs.

A comprehensive overview on the crosstalk between microRNAs and viral pathogenesis and infection

Infections caused by viruses as the smallest infectious agents, pose a major threat to global public health. Viral infections utilize different host mechanisms to facilitate their own propagation and pathogenesis. MicroRNAs (miRNAs), as small noncoding RNA molecules, play important regulatory roles in different diseases, including viral infections. They can promote or inhibit viral infection and have a pro-viral or antiviral role. Also, viral infections can modulate the expression of host miRNAs. Furthermore, viruses from different families evade the host immune response by producing their own miRNAs called viral miRNAs (v-miRNAs). Understanding the replication cycle of viruses and their relation with host miRNAs and v-miRNAs can help to find new treatments against viral infections. In this review, we aim to outline the structure, genome, and replication cycle of various viruses including hepatitis B, hepatitis C, influenza A virus, coronavirus, human immunodeficiency virus, human papillomavirus, herpes simplex virus, Epstein-Barr virus, Dengue virus, Zika virus, and Ebola virus. We also discuss the role of different host miRNAs and v-miRNAs and their role in the pathogenesis of these viral infections.

MicroRNA-focused CRISPR/Cas9 screen identifies miR-142 as a key regulator of Epstein-Barr virus reactivation

Reactivation from latency plays a significant role in maintaining persistent lifelong Epstein-Barr virus (EBV) infection. Mechanisms governing successful activation and progression of the EBV lytic phase are not fully understood. EBV expresses multiple viral microRNAs (miRNAs) and manipulates several cellular miRNAs to support viral infection. To gain insight into the host miRNAs regulating transitions from EBV latency into the lytic stage, we conducted a CRISPR/Cas9-based screen in EBV+ Burkitt lymphoma (BL) cells using anti-Ig antibodies to crosslink the B cell receptor (BCR) and induce reactivation. Using a gRNA library against >1500 annotated human miRNAs, we identified miR-142 as a key regulator of EBV reactivation. Genetic ablation of miR-142 enhanced levels of immediate early and early lytic gene products in infected BL cells. Ago2-PAR-CLIP experiments with reactivated cells revealed miR-142 targets related to Erk/MAPK signaling, including components directly downstream of the B cell receptor (BCR). Consistent with these findings, disruption of miR-142 enhanced SOS1 levels and Mek phosphorylation in response to surface Ig cross-linking. Effects could be rescued by inhibitors of Mek (cobimetinib) or Raf (dabrafenib). Taken together, these results show that miR-142 functionally regulates SOS1/Ras/Raf/Mek/Erk signaling initiated through the BCR and consequently, restricts EBV entry into the lytic cycle.

Immunity and Immune Evasion Mechanisms of Epstein-Barr Virus

Epstein-Barr virus (EBV) is the first human oncogenic virus to be identified, which evades the body's immune surveillance through multiple mechanisms that allow long-term latent infection. Under certain pathological conditions, EBVs undergo a transition from the latent phase to the lytic phase and cause targeted dysregulation of the host immune system, leading to the development of EBV-related diseases. Therefore, an in-depth understanding of the mechanism of developing an immune response to EBV and the evasion of immune recognition by EBV is important for the understanding of the pathogenesis of EBV, which is of great significance for finding strategies to prevent EBV infection, and developing a therapy to treat EBV-associated diseases. In this review, we will discuss the molecular mechanisms of host immunological responses to EBV infection and the mechanisms of EBV-mediated immune evasion during chronic active infection.

MicroRNA-mediated control of Epstein-Barr virus infection and potential diagnostic and therapeutic implications

Herpesviruses, such as Epstein-Barr virus (EBV), encode multiple viral microRNAs that are expressed throughout various infection stages. While much progress has been made in evaluating both the viral and host microRNAs (miRNAs) that are detected during infection as well as elucidating their molecular targets in vitro, our understanding of their contributions to pathogenesis in vivo, viral oncogenesis, and clinical implications for these small molecules remains limited. miRNAs are widely recognized as key regulators of global cellular processes, including apoptosis, cell differentiation, and development of immune responses. This review discusses the roles of miRNAs in EBV infection and current advances in miRNA-based diagnostic and therapeutic strategies potentially applicable toward EBV-associated diseases.

MicroRNA Regulation of Human Herpesvirus Latency

Herpesviruses are ubiquitous human pathogens. After productive (lytic) infection, all human herpesviruses are able to establish life-long latent infection and reactivate from it. Latent infection entails suppression of viral replication, maintenance of the viral genome in infected cells, and the ability to reactivate. Most human herpesviruses encode microRNAs (miRNAs) that regulate these processes during latency. Meanwhile, cellular miRNAs are hijacked by herpesviruses to participate in these processes. The viral or cellular miRNAs either directly target viral transcripts or indirectly affect viral infection through host pathways. These findings shed light on the molecular determinants that control the lytic-latent switch and may lead to novel therapeutics targeting latent infection. We discuss the multiple mechanisms by which miRNAs regulate herpesvirus latency, focusing on the patterns in these mechanisms.