Epstein-Barr virus (EBV) oncoprotein EBNA3C is indispensable for primary B-cell transformation and maintenance of lymphoblastoid cells outgrowth. EBNA3C usurps two putative cellular pathways—cell-cycle and apoptosis, essentially through modulating ubiquitin-mediated protein-degradation or gene transcription. In cancer cells, these two pathways are interconnected with autophagy,—a survival-promoting catabolic network in which cytoplasmic material including mis/un-folded protein aggregates and damaged organelles along with intracellular pathogens are degraded and recycled in lysosomal compartments. Studies have shown that tumor viruses including EBV can manipulate autophagy as a survival strategy. Here, we demonstrate that EBNA3C elevates autophagy, which serves as a prerequisite for apoptotic inhibition and maintenance of cell growth. Using PCR based micro-array we show that EBNA3C globally accelerates autophagy gene transcription under growth limiting conditions. Reanalyzing the ENCODE ChIP-sequencing data (GSE52632 and GSE26386) followed by ChIP-PCR demonstrate that EBNA3C recruits several histone activation epigenetic marks (H3K4me1, H3K4me3, H3K9ac, and H3K27ac) for transcriptional activation of autophagy genes, notably ATG3, ATG5, and ATG7 responsible for autophagosome formation. Moreover, under growth limiting conditions EBNA3C further stimulates the autophagic response through upregulation of a number of tumor suppressor genes, notably cyclin-dependent kinase inhibitors—CDKN1B (p27Kip1) and CDKN2A (p16INK4a) and autophagy mediated cell-death modulators—DRAM1 and DAPK1. Together our data highlight a new role of an essential EBV oncoprotein in regulating autophagy cascade as a survival mechanism and offer novel-targets for potential therapeutic expansion against EBV induced B-cell lymphomas.

Coronaviruses can cause serious respiratory tract infections and may also impact other end organs such as the central nervous system, the lung and the heart. The coronavirus disease 2019 (COVID-19) has had a devastating impact on humanity. Understanding the mechanisms that contribute to the pathogenesis of coronavirus infections, will set the foundation for development of new treatments to attenuate the impact of infections with coronaviruses on host cells and tissues. During infection of host cells, coronaviruses trigger an imbalance between increased production of reactive oxygen species (ROS) and reduced antioxidant host responses that leads to increased redox stress. Subsequently, increased redox stress contributes to reduced antiviral host responses and increased virus-induced inflammation and apoptosis that ultimately drive cell and tissue damage and end organ disease. However, there is limited understanding how different coronaviruses including SARS-CoV-2, manipulate cellular machinery that drives redox responses. This review aims to elucidate the redox mechanisms involved in the replication of coronaviruses and associated inflammation, apoptotic pathways, autoimmunity, vascular dysfunction and tissue damage that collectively contribute to multiorgan damage.

Epstein-Barr virus (EBV) nuclear oncoprotein EBNA3C is essential for B-cell transformation and development of several B-cell lymphomas particularly those are generated in an immuno-compromised background. EBNA3C recruits ubiquitin-proteasome machinery for deregulating multiple cellular oncoproteins and tumor suppressor proteins. Although EBNA3C is found to be ubiquitinated at its N-terminal region and interacts with 20S proteasome, the viral protein is surprisingly stable in growing B-lymphocytes. EBNA3C can also circumvent autophagy-lysosomal mediated protein degradation and subsequent antigen presentation for T-cell recognition. Recently, we have shown that EBNA3C enhances autophagy, which serve as a prerequisite for B-cell survival particularly under growth deprivation conditions. We now demonstrate that proteasomal inhibition by MG132 induces EBNA3C degradation both in EBV transformed B-lymphocytes and ectopic-expression systems. Interestingly, MG132 treatment promotes degradation of two EBNA3 family oncoproteins-EBNA3A and EBNA3C, but not the viral tumor suppressor protein EBNA3B. EBNA3C degradation induced by proteasomal inhibition is partially blocked when autophagy-lysosomal pathway is inhibited. In response to proteasomal inhibition, EBNA3C is predominantly K63linked polyubiquitinated, colocalized with the autophagy-lysosomal fraction in the cytoplasm and participated within p62-LC3B complex, which facilitates autophagy-mediated degradation. We further show that the degradation signal is present at the first 50 residues of the Nterminal region of EBNA3C. Proteasomal inhibition reduces the colony formation ability of this important viral oncoprotein, induces apoptotic cell death and increases transcriptional activation of both latent and lytic gene expression which further promotes viral reactivation from EBV transformed B-lymphocytes. Altogether, this study offers rationale to use proteasome inhibitors as potential therapeutic strategy against multiple EBV associated B-cell lymphomas, where EBNA3C is expressed.

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26 Epstein-Barr virus (EBV) nuclear oncoprotein EBNA3C is essential for B-cell transformation 27 and development of several B-cell lymphomas particularly those are generated in an immuno-28 compromised background. EBNA3C recruits ubiquitin-proteasome machinery for deregulating 29 multiple cellular oncoproteins and tumor suppressor proteins. Although EBNA3C is found to be 30 ubiquitinated at its N-terminal region and interacts with 20S proteasome, the viral protein is 31 surprisingly stable in growing B-lymphocytes. EBNA3C can also circumvent autophagy-lysosomal 32 mediated protein degradation and subsequent antigen presentation for T-cell recognition. Recently, 33 we have shown that EBNA3C enhances autophagy, which serve as a prerequisite for B-cell survival 34 particularly under growth deprivation conditions. We now demonstrate that proteasomal inhibition 35 by MG132 induces EBNA3C degradation both in EBV transformed B-lymphocytes and ectopic-36 expression systems. Interestingly, MG132 treatment promotes degradation of two EBNA3 family 37 oncoproteins -EBNA3A and EBNA3C, but not the viral tumor suppressor protein EBNA3B. EBNA3C 38 degradation induced by proteasomal inhibition is partially blocked when autophagy-lysosomal 39 pathway is inhibited. In response to proteasomal inhibition, EBNA3C is predominantly K63-linked 40 polyubiquitinated, colocalized with the autophagy-lsyosomal fraction in the cytoplasm and 41 participated within p62-LC3B complex, which facilitates autophagy-mediated degradation. We 42 further show that the degradation signal is present at the first 50 residues of the N-terminal region 43 of EBNA3C. Proteasomal inhibition reduces the colony formation ability of this important viral 44 oncoprotein, increases transcriptional activation of both latent and lytic gene expression and 45 induces viral reactivation from EBV transformed B-lymphocytes. Altogether, this study offers 46 rationale to use proteasome inhibitors as potential therapeutic strategy against multiple EBV 47 associated B-cell lymphomas, where EBNA3C is expressed. 48 49 50 3 | P a g e 51 Author Summary 52 Epstein-Barr virus (EBV) establishes latent infection in B-lymphocytes and is associated with 53 a number of human malignancies, both of epithelial and lymphoid origin. EBV encoded EBNA3 54 family of nuclear latent antigens comprising of EBNA3A, EBNA3B, and EBNA3C are unique to 55 immunoblastic lymphomas. While EBNA3A and EBNA3C are involved in blocking many important 56 tumor suppressive mechanisms, EBNA3B exhibits tumor suppressive functions. Although EBNA3 57 proteins, in particular EBNA3C, interact with and employ different protein degradation machineries 58 to induce B-cell lymphomagenesis, these viral proteins are extremely stable in growing B-59 lymphocytes. To this end, we now demonstrate that proteasomal inhibition leads to specifically 60 degradation of oncogenic EBNA3A and EBNA3C proteins, whereas EBNA3B remains unaffected. 61 Upon proteasomal inhibition, EBNA3C degradation occurs via autophagy-lysosomal pathway, 62 thro...