Induction of Multiple miR-200/182 Members in the Brains of Mice Are Associated with Acute Herpes Simplex Virus 1 Encephalitis

Potential diagnostic value of miRNAs in sexually transmitted infections

MiRNAs are small endogenous non-coding RNAs that have been demonstrated to be involved in post-transcriptional gene silencing, regulating a number of metabolic functions in the human body, including immune response, cellular physiology, organ development, angiogenesis, signaling, and other aspects. As popular molecules that have been studied in previous years, given their extensive regulatory functions, miRNAs hold considerable promise as non-invasive biomarkers. Sexually transmitted infections(STIs) are still widespread and have an adverse effect on individuals, communities, and society worldwide. miRNAs in the regulatory networks are generally involved in their molecular processes of formation and development. In this review, we discuss the value of miRNAs for the diagnosis of STIs.

Herpes Simplex Virus 1 MicroRNAs: An Update

BACKGROUND

Herpes simplex virus 1 (HSV-1), an important human pathogen, is capable of latent infection in neurons and productive (lytic) infection in other tissue cells. Once infected with HSV-1, the immune system of the organism cannot eliminate the virus and carries it lifelong. HSV-1 possesses approximately 150 kb of double-stranded linear genomic DNA and can encode at least 70 proteins and 37 mature microRNAs (miRNAs) derived from 18 precursor miRNAs (pre-miRNAs).

SUMMARY

These HSV-1-encoded miRNAs are widely involved in multiple processes in the life cycle of the virus and the host cell, including viral latent and lytic infection, as well as host cell immune signaling, proliferation, and apoptosis.

KEY MESSAGE

In this review, we focused primarily on recent advances in HSV-1-encoded miRNA expression, function, and mechanism, which may provide new research ideas and feasible research methods systemically and comprehensively.

Possible role of CNS microRNAs in Human Mpox virus encephalitis-a mini-review

In May 2022, a re-emerging viral pathogen belonging to the Poxviridae was first reported from the UK, and WHO confirmed the outbreak after the prevalence of the disease increased. As of February 15, 2023, more than 85,000 confirmed cases have been recorded in 110 countries. Due to the spread of the virus across multiple countries, WHO declared the mpox outbreak as a public health emergency. Human mpox virus is an enveloped virus with a linear double-stranded DNA that can cause encephalitis with neurological complications such as pharyngitis, fever, anorexia, adenopathy, vesiculopapular rash, and headache. Dysregulation of microRNAs in viral encephalitis has been reported in a variety of documents. In this mini-review, we aim to discuss the possibility of CNS-related microRNA dysregulation in mpox-related encephalitis.

The Virus-Induced Upregulation of the miR-183/96/182 Cluster and the FoxO Family Protein Members Are Not Required for Efficient Replication of HSV-1

Herpes simplex virus 1 (HSV-1) expresses a large number of miRNAs, and their function is still not completely understood. In addition, HSV-1 has been found to deregulate host miRNAs, which adds to the complexity of the regulation of efficient virus replication. In this study, we comprehensively addressed the deregulation of host miRNAs by massive-parallel sequencing. We found that only miRNAs expressed from a single cluster, miR-183/96/182, are reproducibly deregulated during productive infection. These miRNAs are predicted to regulate a great number of potential targets involved in different cellular processes and have only 33 shared targets. Among these, members of the FoxO family of proteins were identified as potential targets for all three miRNAs. However, our study shows that the upregulated miRNAs do not affect the expression of FoxO proteins, moreover, these proteins were upregulated in HSV-1 infection. Furthermore, we show that the individual FoxO proteins are not required for efficient HSV-1 replication. Taken together, our results indicate a complex and redundant response of infected cells to the virus infection that is efficiently inhibited by the virus.

MiR-155: An Important Regulator of Neuroinflammation

MicroRNAs (miRNAs) are small non-coding RNA molecules that regulate gene expression at the post-transcriptional level and that play an important role in many cellular processes, including modulation of inflammation. MiRNAs are present in high concentrations in the central nervous system (CNS) and are spatially and temporally expressed in a specific way. Therefore, an imbalance in the expression pattern of these small molecules can be involved in the development of neurological diseases. Generally, CNS responds to damage or disease through the activation of an inflammatory response, but many neurological disorders are characterized by uncontrolled neuroinflammation. Many studies support the involvement of miRNAs in the activation or inhibition of inflammatory signaling and in the promotion of uncontrolled neuroinflammation with pathological consequences. MiR-155 is a pro-inflammatory mediator of the CNS and plays an important regulatory role. The purpose of this review is to summarize how miR-155 is regulated and the pathological consequences of its deregulation during neuroinflammatory disorders, including multiple sclerosis, Alzheimer's disease and other neuroinflammatory disorders. Modulation of miRNAs' expression could be used as a therapeutic strategy in the treatment of pathological neuroinflammation.

MicroRNA-155 and antiviral immune responses

The microRNA, miR-155 regulates both adaptive and innate immune responses. In viral infections, miR-155 can affect both innate immunity (interferon response, natural killer cell activity, and macrophage polarization) and adaptive immunity (including generation of anti-viral antibodies, CD8⁺ cytotoxic T lymphocytes, Th17, Th2, Th1, Tfh and Treg cells). In many viral infections, the proper and timely regulation of miR-155 expression is critical for the induction of an effective anti-virus immune response and viral clearance without any harmful immunopathologic consequences. MiR-155 may also exert pro-viral effects, mainly through the inhibition of the anti-viral interferon response. Thus, dysregulated expression of miR-155 can result in virus persistence and disruption of the normal response to viral infections. This review provides a thorough discussion of the role of miR-155 in immune responses and immunopathologic reactions during viral infections, and highlights its potential as a therapeutic target.

Local Immune Control of Latent Herpes Simplex Virus Type 1 in Ganglia of Mice and Man

Herpes simplex virus type 1 (HSV-1) is a prevalent human pathogen. HSV-1 genomes persist in trigeminal ganglia neuronal nuclei as chromatinized episomes, while epithelial cells are typically killed by lytic infection. Fluctuations in anti-viral responses, broadly defined, may underlay periodic reactivations. The ganglionic immune response to HSV-1 infection includes cell-intrinsic responses in neurons, innate sensing by several cell types, and the infiltration and persistence of antigen-specific T-cells. The mechanisms specifying the contrasting fates of HSV-1 in neurons and epithelial cells may include differential genome silencing and chromatinization, dictated by variation in access of immune modulating viral tegument proteins to the cell body, and protection of neurons by autophagy. Innate responses have the capacity of recruiting additional immune cells and paracrine activity on parenchymal cells, for example via chemokines and type I interferons. In both mice and humans, HSV-1-specific CD8 and CD4 T-cells are recruited to ganglia, with mechanistic studies suggesting active roles in immune surveillance and control of reactivation. In this review we focus mainly on HSV-1 and the TG, comparing and contrasting where possible observational, interventional, and in vitro studies between humans and animal hosts.

MiR-200c-3p expression may be associated with worsening of the clinical course of patients with COVID-19

COVID-19 represents a public health emergency, whose mechanism of which is not fully understood. It is speculated that microRNAs may play a crucial role in host cells after infection by SARS-CoV-2. Thus, our study aimed to analyze the expression of miR-200c-3p in saliva samples from patients with COVID-19. One handred eleven samples from patients with COVID-19 were divided into 4 groups. Group I: 39 patients negative for Covid-19; Group II: 37 positive and symptomatic patients, with no indication of hospitalization; Group III: 21 patients with respiratory disorders (hospitalized); Group IV: 14 patients with severe conditions (oxygen therapy). The expression levels of miR-200c-3p were determined using qPCR. We found greater expression of miR-200c-3p in patients in group IV (p<0.0001), and also verified that patients aged ≥42 years had a higher expression of this miR (p=0.013). Logistic regression analysis revealed that the expression of miR-200c-3p and systemic arterial hypertension are factors independently associated with patients in group IV (p<0.0001). Our results suggest that miR-200c-3p is a predictor of severity independent of COVID-19 risk factors, which could represent a way of screening patients affected by SARS-CoV-2.

Toll-like receptor-mediated innate immunity against herpesviridae infection: a current perspective on viral infection signaling pathways

Background

In the past decades, researchers have demonstrated the critical role of Toll-like receptors (TLRs) in the innate immune system. They recognize viral components and trigger immune signal cascades to subsequently promote the activation of the immune system.

Main body

Herpesviridae family members trigger TLRs to elicit cytokines in the process of infection to activate antiviral innate immune responses in host cells. This review aims to clarify the role of TLRs in the innate immunity defense against herpesviridae, and systematically describes the processes of TLR actions and herpesviridae recognition as well as the signal transduction pathways involved.

Conclusions

Future studies of the interactions between TLRs and herpesviridae infections, especially the subsequent signaling pathways, will not only contribute to the planning of effective antiviral therapies but also provide new molecular targets for the development of antiviral drugs.

MicroRNA-146a Is a Wide-Reaching Neuroinflammatory Regulator and Potential Treatment Target in Neurological Diseases

Progressive functional deterioration and loss of neurons underlies neurological diseases and constitutes an important cause of disability and death worldwide. The causes of various types of neurological diseases often share several critical nerve-related cellular mechanisms and pathological features, particularly the neuroinflammatory response in the nervous system. A rapidly growing body of evidence indicates that various microRNAs play pivotal roles in these processes in neurological diseases and might be viable therapeutic targets. Among these microRNAs, microRNA-146a (miR-146a) stands out due to the rapid increase in recent literature on its mechanistic involvement in neurological diseases. In this review, we summarize and highlight the critical role of miR-146a in neurological diseases. MiR-146a polymorphisms are associated with the risk of neurological disease. Alterations in miR-146a expression levels are crucial events in the pathogenesis of numerous neurological diseases that are spatially and temporally diverse. Additionally, the target genes of miR-146a are involved in the regulation of pathophysiological processes in neurological diseases, particularly the neuroinflammatory response. In summary, miR-146a mainly plays a critical role in neuroinflammation during the progression of neurological diseases and might be a prospective biomarker and therapeutic target. Understanding the mechanisms by which miR-146a affects the neuroinflammatory response in different neurological injuries, different cell types, and even different stages of certain neurological diseases will pave the way for its use as a therapeutic target in neurodegenerative diseases.

Integration analysis of a miRNA-mRNA expression in A549 cells infected with a novel H3N2 swine influenza virus and the 2009 H1N1 pandemic influenza virus

Swine are reservoirs for anthropogenic/zoonotic influenza viruses, and the prevalence and repeated introduction of the 2009 H1N1 pandemic influenza virus (pdm/09) into pigs raises the possibility of generating novel swine influenza viruses with the potential to infect humans. However, studies aiming to identify miRNAs involved in the transfer of novel swine influenza virus infection to human cells are rare. In this investigation, from the view of small RNA, microarrays and high-throughput sequencing were used to detect differentially expressed miRNAs and mRNAs after human lung epithelial cells were infected with the following three stains of influenza viruses: a novel H3N2 swine influenza virus reassorted with pdm/09 fragments, pdm/09 and classical swine influenza virus. A miRNA-mRNA interaction map was generated to show the correlation between miRNAs related to infection by the viruses with human infective potential/capability. The expression of 4 miRNAs (hsa-miR-96-5p, hsa-miR-140-5p, hsa-miR-30a-3p and hsa-miR-582-5p) and 5 relevant mRNAs (RCC1, ERVFRD-1, RANBP1, SCARB2 and RPS29) was determined. The integration analysis indicated that these candidates have rarely been reported to be associated with influenza virus. Focusing on miRNA expression changes could reveal novel reassortant viruses with human infective potential that may provide insight into future pandemics.

MicroRNAs in Neuroinflammation: Implications in Disease Pathogenesis, Biomarker Discovery and Therapeutic Applications

The central nervous system can respond to threat via the induction of an inflammatory response. Under normal circumstances this response is tightly controlled, however uncontrolled neuroinflammation is a hallmark of many neurological disorders. MicroRNAs are small non-coding RNA molecules that are important for regulating many cellular processes. The ability of microRNAs to modulate inflammatory signaling is an area of ongoing research, which has gained much attention in recent years. MicroRNAs may either promote or restrict inflammatory signaling, and either exacerbate or ameliorate the pathological consequences of excessive neuroinflammation. The aim of this review is to summarize the mode of regulation for several important and well-studied microRNAs in the context of neuroinflammation, including miR-155, miR-146a, miR-124, miR-21 and let-7. Furthermore, the pathological consequences of miRNA deregulation during disorders that feature neuroinflammation are discussed, including Multiple Sclerosis, Alzheimer’s disease, Parkinson’s disease, Prion diseases, Japanese encephalitis, Herpes encephalitis, ischemic stroke and traumatic brain injury. There has also been considerable interest in the use of altered microRNA signatures as biomarkers for these disorders. The ability to modulate microRNA expression may even serve as the basis for future therapeutic strategies to help treat pathological neuroinflammation.

MiR-155-5p modulates HSV-1 replication via the epigenetic regulation of SRSF2 gene expression

A previous study reported that miR-155-5p knockout mice were more resistant to herpes simplex virus type I (HSV-1) infection. However, the exact underlying molecular mechanism remains to be elucidated. Here, we demonstrated that HSV-1 infection upregulates miR-155-5p expression. By binding to the promoter of serine/arginine-rich splicing factor 2 (SRSF2), which is an important transcriptional activator of HSV-1 genes that was previously reported by our group, and altering the histone modification located near the transcription start site (TSS) of the SRSF2 gene, miR-155-5p promotes the transcription of the SRSF2 gene, ultimately increasing viral replication and viral gene expression. Our results provide insight for an understanding of the roles and molecular mechanism of miR-155-5p in HSV-1 replication and the epigenetic control of SRSF2 gene expression.

Isolation of Viral-Infected Brain Regions for miRNA Profiling from Formalin-Fixed Paraffin-Embedded Tissues by Laser Capture Microdissection

Brain is a highly heterogeneous organ with numerous layers of specialized cells. Viral infection further adds complexity to downstream analysis because only a subpopulation of the brain is infected. In these instances, molecular changes that occur within infected cells are not truly reflected when whole tissue is used for downstream analysis. Laser capture microdissection (LCM) is a tool that allows for the selection and isolation of cells or regions of interest as determined by microscopic observation. It provides a platform for visually selecting the tissue that truly represents the material one wishes to study, such as viral infected cells. Formalin-fixed paraffin-embedded viral-infected tissue allows for safe handling and processing by LCM. Here, we describe a method whereby viral-infected regions of the brain were specifically isolated by LCM from the rest of the FFPE tissue. The isolated regions were then used to extract RNA for microRNA profiling. This approach can be applied to study microRNA changes from any viral infection in any given tissue.

Herpes Simplex Virus 1 Deregulation of Host MicroRNAs

Viruses utilize microRNAs (miRNAs) in a vast variety of possible interactions and mechanisms, apparently far beyond the classical understanding of gene repression in humans. Likewise, herpes simplex virus 1 (HSV-1) expresses numerous miRNAs and deregulates the expression of host miRNAs. Several HSV-1 miRNAs are abundantly expressed in latency, some of which are encoded antisense to transcripts of important productive infection genes, indicating their roles in repressing the productive cycle and/or in maintenance/reactivation from latency. In addition, HSV-1 also exploits host miRNAs to advance its replication or repress its genes to facilitate latency. Here, we discuss what is known about the functional interplay between HSV-1 and the host miRNA machinery, potential targets, and the molecular mechanisms leading to an efficient virus replication and spread.

Deep sequencing and miRNA profiles in alcohol-induced neuroinflammation and the TLR4 response in mice cerebral cortex

Alcohol abuse can induce brain injury and neurodegeneration, and recent evidence shows the participation of immune receptors toll-like in the neuroinflammation and brain damage. We evaluated the role of miRNAs as potential modulators of the neuroinflammation associated with alcohol abuse and the influence of the TLR4 response. Using mice cerebral cortex and next-generation sequencing (NGS), we identified miRNAs that were differentially expressed in the chronic alcohol-treated versus untreated WT or TLR4-KO mice. We observed a differentially expression of miR-183 Cluster (C) (miR-96/-182/-183), miR-200a and miR-200b, which were down-regulated, while mirR-125b was up-regulated in alcohol-treated WT versus (vs.) untreated mice. These miRNAs modulate targets genes related to the voltage-gated sodium channel, neuron hyperexcitability (Nav1.3, Trpv1, Smad3 and PP1-γ), as well as genes associated with innate immune TLR4 signaling response (Il1r1, Mapk14, Sirt1, Lrp6 and Bdnf). Functional enrichment of the miR-183C and miR-200a/b family target genes, revealed neuroinflammatory pathways networks involved in TLR4 signaling and alcohol abuse. The changes in the neuroinflammatory targets genes associated with alcohol abuse were mostly abolished in the TLR4-KO mice. Our results show the relationship between alcohol intake and miRNAs expression and open up new therapeutically targets to prevent deleterious effects of alcohol on the brain.

Long noncoding RNA MALAT1 in exosomes drives regenerative function and modulates inflammation-linked networks following traumatic brain injury

BACKGROUND

Neuroinflammation is a common therapeutic target for traumatic brain injury (TBI) due to its contribution to delayed secondary cell death and has the potential to occur for years after the initial insult. Exosomes from adipose-derived stem cells (hASCs) containing the long noncoding RNA MALAT1 are a novel, cell-free regenerative approach to long-term recovery after traumatic brain injury (TBI) that have the potential to modulate inflammation at the genomic level. The long noncoding RNA MALAT1 has been shown to be an important component of the secretome of hASCs.

METHODS

We isolated exosomes from hASC containing or depleted of MALAT1. The hASC-derived exosomes were then administered intravenously to rats following a mild controlled cortical impact (CCI). We followed the rats with behavior, in vivo imaging, histology, and RNA sequencing (RNA Seq).

RESULTS

Using in vivo imaging, we show that exosomes migrate into the spleen within 1 h following administration and enter the brain several hours later following TBI. Significant recovery of function on motor behavior as well as a reduction in cortical brain injury was observed after TBI in rats treated with exosomes. Treatment with either exosomes depleted of MALAT1 or conditioned media depleted of exosomes showed limited regenerative effects, demonstrating the importance of MALAT1 in exosome-mediated recovery. Analysis of the brain and spleen transcriptome using RNA Seq showed MALAT1-dependent modulation of inflammation-related pathways, cell cycle, cell death, and regenerative molecular pathways. Importantly, our data demonstrates that MALAT1 regulates expression of other noncoding RNAs including snoRNAs.

CONCLUSION

We demonstrate that MALAT1 in hASC-derived exosomes modulates multiple therapeutic targets, including inflammation, and has tremendous therapeutic potential for treatment of TBI.

miR-21-3p Regulates Influenza A Virus Replication by Targeting Histone Deacetylase-8

Influenza A virus (IAV) is responsible for severe morbidity and mortality in animals and humans worldwide. miRNAs are a class of small noncoding single-stranded RNA molecules that can negatively regulate gene expression and play important roles in virus-host interaction. However, the roles of miRNAs in IAV infection are still not fully understood. Here, we profiled the cellular miRNAs of A549 cells infected with A/goose/Jilin/hb/2003 (H5N1) and a comparison A/Beijing/501/2009 (H1N1). miRNA microarray and quantitative PCR analysis showed that several miRNAs were differentially expressed in A549 cells during IAV infection. Subsequently, we demonstrated that IAV replication was essential for the regulation of these miRNAs, and bioinformatic analysis revealed that the targets of these miRNAs affected biological processes relevant to IAV replication. Specifically, miR-21-3p was found to be down-regulated in IAV-infected A549 cells and selected for further detailed analysis. Target prediction and functional study illustrated that miR-21-3p repressed the expression of HDAC8 by targeting its 3′UTR. Furthermore, we confirmed miR-21-3p could promote virus replication, which was similar to the result of knocking down HDAC8, indicating that miR-21-3p promoted IAV replication by suppressing HDAC8 expression. Altogether, our results suggest a potential host defense against IAV through down-regulation of miR-21-3p.

MicroRNA-182 inhibits HCMV replication through activation of type I IFN response by targeting FOXO3 in neural cells

Human cytomegalovirus (HCMV) has led to kinds of clinical disorders and great morbidity worldwide, such as sensorineural hearing loss (SNHL), mental retardation, and developmental delays in immunocompromised individuals. Congenital HCMV infection is a leading cause of birth defects, primarily manifesting as neurological disorders. Previous studies reported that HCMV has evolved a variety of mechanisms to evade the immune system, such as dysregulation of miRNAs. However, reports concerning the role of miRNA in HCMV infection in neural cells are limited. Here, we reported that a host microRNA, miR-182, was significantly up-regulated by HCMV infection in U-251MG and NPCs cells. Subsequently, our results of in vitro and in vivo experiments demonstrated that miR-182 was a positive regulator of interferon regulatory factor 7 (IRF7) by directly targeting FOXO3, resulting in the induction of IFN-I response and suppression of HCMV replication in neural cells. Taken together, our findings provide detailed molecular mechanisms of the antiviral function of miR-182 against HCMV infection in neural cells, and suggest an intrinsic anti-HCMV therapeutic target.

Are miRNAs critical determinants in herpes simplex virus pathogenesis?

miRNAs are small noncoding RNA that play a crucial role in gene regulation by inhibiting translation or promoting mRNA degradation. Viruses themselves express miRNAs that can target either the host or viral mRNA transcriptome. Moreover, viral infection of cells causes a drastic change in host miRNAs. This complex interaction between the host and viruses often favors the virus to evade immune elimination and favors the establishment and maintenance of latency. In this review we discuss the function of both host and viral miRNAs in regulating herpes simplex virus pathogenesis and also discuss the prospect of using miRNAs as biomarkers and therapeutic tools.

Emerging roles of syndecan 2 in epithelial and mesenchymal cancer progression

Syndecan 2 (SDC2) belongs to a four-member family of evolutionary conserved small type I transmembrane proteoglycans consisting of a protein core to which glycosaminoglycan chains are covalently attached. SDC2 is a cell surface heparan sulfate proteoglycan, which is increasingly drawing attention for its distinct characteristics and its participation in numerous cell functions, including those related to carcinogenesis. Increasing evidence suggests that the role of SDC2 in cancer pathogenesis is dependent on cancer tissue origin rendering its use as a biomarker/therapeutic target feasible. This mini review discusses the mechanisms, through which SDC2, in a distinct manner, modulates complex signalling networks to affect cancer progression. © 2017 IUBMB Life, 69(11):824-833, 2017.

Expression of miR-155 associated with Toll-like receptors 3, 7, and 9 transcription in the olfactory bulbs of cattle naturally infected with BHV5

Bovine herpesvirus 5 (BHV5) infection of young cattle is frequently associated with fatal neurological disease and, as such, represents an attractive model for studying the pathogenesis of viral-induced meningoencephalitis. Following replication in the nasal mucosa, BHV5 invades the central nervous system (CNS) mainly through the olfactory pathway. The innate immune response triggered by the host face to virus replication through the olfactory route is poorly understood. Recently, an upregulation of conserved pathogen-associated molecular pattern, as Toll-like receptors (TLRs), has been demonstrated in the CNS of BHV5 experimentally infected cows. A new perspective to understand host-pathogen interactions has emerged elucidating microRNAs (miRNAs) network that interact with innate immune response during neurotropic viral infections. In this study, we demonstrated a link between the expression of TLRs 3, 7, and 9 and miR-155 transcription in the olfactory bulbs (OB) of 16 cows suffering from acute BHV5-induced neurological disease. The OBs were analyzed for viral antigens and genome, miR-155 and TLR 3, 7, and 9 expression considering three major regions: olfactory receptor neurons (ORNs), glomerular layer (GL), and mitral cell layer (ML). BHV5 antigens and viral genomes, corresponding to glycol-C gene, were detected in all OBs regions by fluorescent antibody assay (FA) and PCR, respectively. TLR 3, 7, and 9 transcripts were upregulated in ORNs and ML, yet only ORN layers revealed a positive correlation between TLR3 and miR-155 transcription. In ML, miR-155 correlated positively with all TLRs studied. Herein, our results evidence miR-155 transcription in BHV5 infected OB tissue associated to TLRs expression specifically ORNs which may be a new window for further studies.

Viral Ubiquitin Ligase Stimulates Selective Host MicroRNA Expression by Targeting ZEB Transcriptional Repressors

Infection with herpes simplex virus-1 (HSV-1) brings numerous changes in cellular gene expression. Levels of most host mRNAs are reduced, limiting synthesis of host proteins, especially those involved in antiviral defenses. The impact of HSV-1 on host microRNAs (miRNAs), an extensive network of short non-coding RNAs that regulate mRNA stability/translation, remains largely unexplored. Here we show that transcription of the miR-183 cluster (miR-183, miR-96, and miR-182) is selectively induced by HSV-1 during productive infection of primary fibroblasts and neurons. ICP0, a viral E3 ubiquitin ligase expressed as an immediate-early protein, is both necessary and sufficient for this induction. Nuclear exclusion of ICP0 or removal of the RING (really interesting new gene) finger domain that is required for E3 ligase activity prevents induction. ICP0 promotes the degradation of numerous host proteins and for the most part, the downstream consequences are unknown. Induction of the miR-183 cluster can be mimicked by depletion of host transcriptional repressors zinc finger E-box binding homeobox 1 (ZEB1)/-crystallin enhancer binding factor 1 (δEF1) and zinc finger E-box binding homeobox 2 (ZEB2)/Smad-interacting protein 1 (SIP1), which we establish as new substrates for ICP0-mediated degradation. Thus, HSV-1 selectively stimulates expression of the miR-183 cluster by ICP0-mediated degradation of ZEB transcriptional repressors.

Growth of malignant extracranial tumors alters microRNAome in the prefrontal cortex of TumorGraft mice

A wide array of central nervous system complications, neurological deficits, and cognitive impairments occur and persist as a result of systemic cancer and cancer treatments. This condition is known as chemo brain and it affects over half of cancer survivors. Recent studies reported that cognitive impairments manifest before chemotherapy and are much broader than chemo brain alone, thereby adding in tumor brain as a component. The molecular mechanisms of chemo brain are under-investigated, and the mechanisms of tumor brain have not been analyzed at all. The frequency and timing, as well as the long-term persistence, of chemo brain and tumor brain suggest they may be epigenetic in nature. MicroRNAs, small, single-stranded non-coding RNAs, constitute an important part of the cellular epigenome and are potent regulators of gene expression. miRNAs are crucial for brain development and function, and are affected by a variety of different stresses, diseases and conditions. However, nothing is known about the effects of extracranial tumor growth or chemotherapy agents on the brain microRNAome. We used the well-established TumorGraft ™ mouse models of triple negative (TNBC) and progesterone receptor positive (PR+BC) breast cancer, and profiled global microRNAome changes in tumor-bearing mice upon chemotherapy, as compared to untreated tumor-bearing mice and intact mice. Our analysis focused on the prefrontal cortex (PFC), based on its roles in memory, learning, and executive functions, and on published data showing the PFC is a target in chemo brain. This is the first study showing that tumor presence alone significantly impacted the small RNAome of PFC tissues. Both tumor growth and chemotherapy treatment affected the small RNAome and altered levels of miRNAs, piRNAs, tRNAs, tRNA fragments and other molecules involved in post-transcriptional regulation of gene expression. Amongst those, miRNA changes were the most pronounced, involving several miRNA families, such as the miR-200 family and miR-183/96/182 cluster; both were deregulated in tumor-bearing and chemotherapy-treated animals. We saw that miRNA deregulation was associated with altered levels of brain-derived neurotrophic factor (BDNF), which plays an important role in cognition and memory and is one of the known miRNA targets. BDNF downregulation has been associated with an array of neurological conditions and could be one of the mechanisms underlying tumor brain and chemo brain. In the future our study could serve as a roadmap for further analysis of cancer and chemotherapy's neural side effects, and differentially expressed miRNAs should be explored as potential tumor brain and chemo brain biomarkers.