Regulatory effect of m6 A modification on different viruses

RNA N6-methyladenosine methylation in influenza A virus infection

Influenza A virus (IAV) is a negative-sense single-stranded RNA virus that causes acute lung injury and acute respiratory distress syndrome, posing a serious threat to both animal and human health. N6-methyladenosine (m6A), a prevalent and abundant post-transcriptional methylation of RNA in eukaryotes, plays a crucial regulatory role in IAV infection by altering viral RNA and cellular transcripts to affect viral infection and the host immune response. This review focuses on the molecular mechanisms underlying m6A modification and its regulatory function in the context of IAV infection and the host immune response. This will provide a better understanding of virus-host interactions and offer insights into potential anti-IAV strategies.

The regulation of antiviral innate immunity through non-m6A RNA modifications

The post-transcriptional RNA modifications impact the dynamic regulation of gene expression in diverse biological and physiological processes. Host RNA modifications play an indispensable role in regulating innate immune responses against virus infection in mammals. Meanwhile, the viral RNAs can be deposited with RNA modifications to interfere with the host immune responses. The N6-methyladenosine (m6A) has boosted the recent emergence of RNA epigenetics, due to its high abundance and a transcriptome-wide widespread distribution in mammalian cells, proven to impact antiviral innate immunity. However, the other types of RNA modifications are also involved in regulating antiviral responses, and the functional roles of these non-m6A RNA modifications have not been comprehensively summarized. In this Review, we conclude the regulatory roles of 2'-O-methylation (Nm), 5-methylcytidine (m5C), adenosine-inosine editing (A-to-I editing), pseudouridine (Ψ), N1-methyladenosine (m1A), N7-methylguanosine (m7G), N6,2'-O-dimethyladenosine (m6Am), and N4-acetylcytidine (ac4C) in antiviral innate immunity. We provide a systematic introduction to the biogenesis and functions of these non-m6A RNA modifications in viral RNA, host RNA, and during virus-host interactions, emphasizing the biological functions of RNA modification regulators in antiviral responses. Furthermore, we discussed the recent research progress in the development of antiviral drugs through non-m6A RNA modifications. Collectively, this Review conveys knowledge and inspiration to researchers in multiple disciplines, highlighting the challenges and future directions in RNA epitranscriptome, immunology, and virology.

HPV E7-drived ALKBH5 promotes cervical cancer progression by modulating m6A modification of PAK5

Human papillomavirus (HPV) infection is a causative agent of cervical cancer (CC). N6-methyladenosine (m6A) modification is implicated in carcinogenesis and tumor progression. However, the involvement of m6A modification in HPV-involved CC remains unclear. Here we showed that HPV E6/7 oncoproteins affected the global m6A modification and E7 specifically promoted the expression of ALKBH5. We found that ALKBH5 was significantly upregulated in CC and might serve as a valuable prognostic marker. Forced expression of ALKBH5 enhanced the malignant phenotypes of CC cells. Mechanistically, we discovered that E7 increased ALKBH5 expression through E2F1-mediated activation of the H3K27Ac and H3K4Me3 histone modifications, as well as post-translational modification mediated by DDX3. ALKBH5-mediated m6A demethylation enhanced the expression of PAK5. The m6A reader YTHDF2 bound to PAK5 mRNA and regulated its stability in an m6A-dependent manner. Moreover, ALKBH5 promoted tumorigenesis and metastasis of CC by regulating PAK5. Overall, our findings herein demonstrate a significant role of ALKBH5 in CC progression in HPV-positive cells. Thus, we propose that ALKBH5 may serve as a prognostic biomarker and therapeutic target for CC patients.

Pseudorabies virus exploits N6-methyladenosine modification to promote viral replication

Introduction

Pseudorabies virus (PRV) is the pathogenic virus of porcine pseudorabies (PR), belonging to the Herpesviridae family. PRV has a wide range of hosts and in recent years has also been reported to infect humans. N⁶-methyladenosine (m⁶A) modification is the major pathway of RNA post-transcriptional modification. Whether m⁶A modification participates in the regulation of PRV replication is unknown.

Methods

Here, we investigated that the m⁶A modification was abundant in the PRV transcripts and PRV infection affected the epitranscriptome of host cells. Knockdown of cellular m⁶A methyltransferases METTL3 and METTL14 and the specific binding proteins YTHDF2 and YTHDF3 inhibited PRV replication, while silencing of demethylase ALKBH5 promoted PRV output. The overexpression of METTL14 induced more efficient virus proliferation in PRV-infected PK15 cells. Inhibition of m⁶A modification by 3-deazaadenosine (3-DAA), a m⁶A modification inhibitor, could significantly reduce viral replication.

Results and Discussion

Taken together, m⁶A modification played a positive role in the regulation of PRV replication and gene expression. Our research revealed m⁶A modification sites in PRV transcripts and determined that m⁶A modification dynamically mediated the interaction between PRV and host.

Dynamic transcriptome analyses reveal m6A regulated immune non-coding RNAs during dengue disease progression

Dengue infection is one of the most prevalent arthropod-borne viral diseases, which can result in severe complications. Identification of genes and long non-coding RNAs (lncRNAs) involved in dengue infection would help in deciphering potential mechanisms responsible for the disease progression. We comprehensively analyzed the dynamic transcriptome during dengue disease progression and identified critical genes and lncRNAs with expression perturbations. Our findings revealed that the expression of genes (i.e., CCR10 and GNG7) and lncRNAs (i.e., CTBP1-AS and MAFG-AS1) were potentially regulated by m6A RNA methylation. Interestingly, dengue viral proteins prevalently interact with genes or lncRNAs with expression perturbations, which are involved in cell cycle, inflammation signaling pathways and immune response. Dynamically expressed genes and lncRNAs were likely to locate in the central regions of human protein-protein network, which play crucial roles in mediating signaling spread and helping viral replication. Immune microenvironments analysis revealed that plasma cells levels were increased and T cells infiltrations were decreased during dengue disease progression. Dynamically expressed genes and lncRNAs were correlated with immune cell infiltrations. Moreover, network analysis reveals the associations between dengue viral infections and human complex diseases (i.e., digestive diseases and neoplasms). Our comprehensive transcriptome analysis of dengue disease progression identified potential gene and lncRNA biomarkers, providing novel insights for understanding the pathogenesis of and developing effective therapeutic strategies for dengue infection.

RNA modifications: importance in immune cell biology and related diseases

RNA modifications have become hot topics recently. By influencing RNA processes, including generation, transportation, function, and metabolization, they act as critical regulators of cell biology. The immune cell abnormality in human diseases is also a research focus and progressing rapidly these years. Studies have demonstrated that RNA modifications participate in the multiple biological processes of immune cells, including development, differentiation, activation, migration, and polarization, thereby modulating the immune responses and are involved in some immune related diseases. In this review, we present existing knowledge of the biological functions and underlying mechanisms of RNA modifications, including N⁶-methyladenosine (m⁶A), 5-methylcytosine (m⁵C), N¹-methyladenosine (m¹A), N⁷-methylguanosine (m⁷G), N⁴-acetylcytosine (ac⁴C), pseudouridine (Ψ), uridylation, and adenosine-to-inosine (A-to-I) RNA editing, and summarize their critical roles in immune cell biology. Via regulating the biological processes of immune cells, RNA modifications can participate in the pathogenesis of immune related diseases, such as cancers, infection, inflammatory and autoimmune diseases. We further highlight the challenges and future directions based on the existing knowledge. All in all, this review will provide helpful knowledge as well as novel ideas for the researchers in this area.

EBV Exploits RNA m6A Modification to Promote Cell Survival and Progeny Virus Production During Lytic Cycle

N6-methyladenosine (m⁶A) mediates various biological processes by affecting RNA stability, splicing, and translational efficiency. The roles of m⁶A modification in Epstein-Barr virus (EBV) infection in the lytic phase are unclear. Here, knockout of the m⁶A methyltransferase, N6-methyladenosine methyltransferase-like 3 (METTL3), or inhibition of methylation by DAA or UZH1a decreased the expression of viral lytic proteins and reduced progeny virion production. Interestingly, cell growth and viability were decreased by induction of the lytic cycle in METTL3-knockout or inhibitor-treated cells. Apoptosis was induced in those conditions possibly because of a decreased level of the anti-apoptotic viral protein, BHRF1. Therefore, m⁶A shows potential as a target of lytic induction therapy for EBV-associated cancers, including Burkitt lymphoma.

Identification and Characterization of BmNPV m6A Sites and Their Possible Roles During Viral Infection

Bombyx mori nucleopolyhedrovirus (BmNPV) is one of the most serious pathogens and causes serious economic losses in sericulture. At present, there is no epigenetic modification of BmNPV transcripts, especially of m6A, and this modification mediates diverse cellular and viral functions. This study showed that m6A modifications are widespread in BmNPV transcripts in virally infected cells and the identified m6A peaks with a conserved RRACH sequence. m6A sites predominantly appear in the coding sequences (CDS) and the 3'-end of CDS. About 37% of viral genes with m6A sites deleted from the viral genome did not produce any infectious virions in KOV-transfected cells. Among the viral genes related to replication and proliferation, ie-1 mRNA was identified with a higher m6A level than other viral genes. The m6A sites in the ie-1 mRNA may be negatively related to the protein expression. Viral replication was markedly inhibited in cells overexpressed with BmYTHDF3 in a dose-dependent manner, and a contrary effect was found in si-BmYTHDF3-transfected cells. Collectively, the identification of putative m6A modification in BmNPV transcripts provides a foundation for comprehensively understanding the viral infection, replication, and pathobiology in silkworms.