Figure 9 - uploaded by Masanao Murakami
Content may be subject to copyright.
Both EBNA3C and Cyclin D1 are required for cell-cycle progression in EBV transformed cells. (A) Lentivirus transduced short hairpin RNA vectors knock down EBNA3C and Cyclin D1 in EBV transformed LCLs. Transduction with sh-RNA-containing lentivirus and selection of EBV-infected cells (LCL1) with puromycin resulted in stable cell lines expressing specific si-RNA against EBNA3C (LCL1_sh-E3C), cyclin D1 (LCL1_shCyD1) and sh-RNA sequence that lacks any complementary sequences in the human genome (LCL1_sh-Cont). The selected cells with GFP fluorescence were monitored by fluorescent microscopy. (B) Western blots showing the expression levels of EBNA3C, pRb, Cyclin D1, Cyclin D2 and Cyclin D3 in LCLs. GAPDH was used as the loading control. (C) Approximately 1 million cells were plated into each well of the 6-well plates and cultured at 37uC in complete medium without puromycin. Viable cells from each well were counted by trypan blue exclusion method daily for twenty days using an automated cell counter. The results shown are representative of two independent experiments. Error bars show standard deviations. doi:10.1371/journal.ppat.1001275.g009
Source publication
EBNA3C, one of the Epstein-Barr virus (EBV)-encoded latent antigens, is essential for primary B-cell transformation. Cyclin D1, a key regulator of G1 to S phase progression, is tightly associated and aberrantly expressed in numerous human cancers. Previously, EBNA3C was shown to bind to Cyclin D1 in vitro along with Cyclin A and Cyclin E. In the pr...
Contexts in source publication
Context 1
... exploits Cyclin D1/CDK6 to promote LCL proliferation by inactivating pRb. To address this, LCLs were stably transduced with lentiviruses that express short hairpin RNA to silence either EBNA3C (Sh-E3C) or cyclin D1 (Sh-CyD1). The Sh-Control RNA is not complementary to human genome sequences. Stable transduction was verified by GFP expression (Fig. 9A). The expression levels of knocked down genes among these cells were then detected by Western blot analysis (Fig. 9B). The results showed that the level of EBNA3C or Cyclin D1 was knocked down by sh-RNA whereas LCL1 transduced with sh- Figure 8. EBNA3C coupled with Cyclin D1/CDK6 complex nullifies the growth suppressive effect by pRb. ...
Context 2
... with lentiviruses that express short hairpin RNA to silence either EBNA3C (Sh-E3C) or cyclin D1 (Sh-CyD1). The Sh-Control RNA is not complementary to human genome sequences. Stable transduction was verified by GFP expression (Fig. 9A). The expression levels of knocked down genes among these cells were then detected by Western blot analysis (Fig. 9B). The results showed that the level of EBNA3C or Cyclin D1 was knocked down by sh-RNA whereas LCL1 transduced with sh- Figure 8. EBNA3C coupled with Cyclin D1/CDK6 complex nullifies the growth suppressive effect by pRb. A-B) Saos-2 cells were transfected with expression plasmids for myc-tagged pRb, flag-tagged Cyclin D1 and CDK6 and ...
Context 3
... had levels similar to LCL1 (Fig. 9B). The results also showed that pRb expression levels were slightly increased in both EBNA3C and Cyclin D1 knocked down samples, whereas there were no alterations observed for other Cyclin D expression levels (Fig. 9B). In order to determine whether both EBNA3C and Cyclin D1 are critical to maintain the proliferation of EBV transformed ...
Context 4
... had levels similar to LCL1 (Fig. 9B). The results also showed that pRb expression levels were slightly increased in both EBNA3C and Cyclin D1 knocked down samples, whereas there were no alterations observed for other Cyclin D expression levels (Fig. 9B). In order to determine whether both EBNA3C and Cyclin D1 are critical to maintain the proliferation of EBV transformed cells, a proliferation analysis was done (Fig. 9C). The results showed that the proliferation rate of both wild-type LCL1 and LCL1 infected with the lentivirus control sh-RNA (Sh- Control) expressing physiological ...
Context 5
... pRb expression levels were slightly increased in both EBNA3C and Cyclin D1 knocked down samples, whereas there were no alterations observed for other Cyclin D expression levels (Fig. 9B). In order to determine whether both EBNA3C and Cyclin D1 are critical to maintain the proliferation of EBV transformed cells, a proliferation analysis was done (Fig. 9C). The results showed that the proliferation rate of both wild-type LCL1 and LCL1 infected with the lentivirus control sh-RNA (Sh- Control) expressing physiological level of both EBNA3C and Cyclin D1 was significantly higher than that of LCLs with Sh-E3C and Sh-CyD1 (Fig. 9C). In agreement with the previously published results [20,49], ...
Context 6
... proliferation of EBV transformed cells, a proliferation analysis was done (Fig. 9C). The results showed that the proliferation rate of both wild-type LCL1 and LCL1 infected with the lentivirus control sh-RNA (Sh- Control) expressing physiological level of both EBNA3C and Cyclin D1 was significantly higher than that of LCLs with Sh-E3C and Sh-CyD1 (Fig. 9C). In agreement with the previously published results [20,49], we also observed that the proliferation rate of LCLs containing Sh-E3C with reduced levels of EBNA3C expression was approximately 3 fold slower than that of control cell-lines (Fig. 9C). Interestingly, the proliferation rate of LCLs with Sh-CyD1 was 50% higher than LCLs with ...
Context 7
... level of both EBNA3C and Cyclin D1 was significantly higher than that of LCLs with Sh-E3C and Sh-CyD1 (Fig. 9C). In agreement with the previously published results [20,49], we also observed that the proliferation rate of LCLs containing Sh-E3C with reduced levels of EBNA3C expression was approximately 3 fold slower than that of control cell-lines (Fig. 9C). Interestingly, the proliferation rate of LCLs with Sh-CyD1 was 50% higher than LCLs with Sh-E3C and only about 1.5 fold lower than that of control. This suggests that other D-type cyclins might be involved in LCL growth, particularly Cyclin D2 which was shown earlier to be associated in EBV mediated lymphomagenesis and probably ...
Similar publications
The development and differentiation of steroidogenic organs are controlled by Ad4BP/SF-1 (adrenal 4 binding protein/steroidogenic factor 1). Besides, lysosomal activity is required for steroidogenesis and also enables adrenocortical cell to survive during stress. However, the role of lysosomal activity on steroidogenic cell growth is as yet unknown...
Differentiation of trophoblast giant cells in the rodent placenta is accompanied by exit from the mitotic cell cycle and onset of endoreduplication. Commitment to giant cell differentiation is under developmental control, involving down-regulation of Id1 and Id2, concomitant with up-regulation of the basic helix-loop-helix factor Hxt and acquisitio...
Hepatitis B virus X protein (HBx) has been previously demonstrated to be associated with the regulation of cell proliferation; however, the exact mechanisms underlying this effect remain unclear. The present study aimed to investigate the regulatory mechanism of HBx on the cycle progression of primary renal tubular epithelial cells. Primary renal t...
Citations
... EBNA3C promotes cell proliferation by stabilizing cyclin D1 and cyclin D2. It stabilizes cyclin D1 by inhibiting its polyubiquitination, inhibiting GSK-3β, which enhances cyclin D1 nuclear localization, and promoting the proteasomal degradation of RASSF1A, a tumor suppressor protein involved in cyclin D1 regulation [60][61][62]. EBNA3C also increases cyclin D2 stability by affecting the proteasomal degradation of Bcl6 [63]. Additionally, EBNA3C promotes cell proliferation by stabilizing Pim-1, inhibiting its proteasomal degradation, and ultimately leading to the downregulation of the cell cycle inhibitor p21/WAF1 [64]. ...
... Direct Interactions: USP46/USP12: EBNA3C interacts with the USP46/USP12 DUB complex, leading to EBV-associated oncogenesis [66]. Cyclin D1: EBNA3C inhibits the polyubiquitination of cyclin D1 and stabilizes it [60][61][62]. Bcl6: EBNA3C modifies the proteasomal degradation Bcl6, causing a secondary increase in cyclin D2 stability [63]. ...
The Herpesviridae include the Epstein–Barr Virus (EBV) and the Kaposi Sarcoma-associated Herpesvirus (KSHV), both of which are oncogenic gamma-herpesviruses. These viruses manipulate host cellular mechanisms, including through ubiquitin-mediated pathways, to promote viral replication and oncogenesis. Ubiquitin, a regulatory protein which tags substrates for degradation or alters their function, is manipulated by both EBV and KSHV to facilitate viral persistence and cancer development. EBV infects approximately 90% of the global population and is implicated in malignancies including Burkitt lymphoma (BL), Hodgkin lymphoma (HL), post-transplant lymphoproliferative disorder (PTLD), and nasopharyngeal carcinoma. EBV latency proteins, notably LMP1 and EBNA3C, use ubiquitin-mediated mechanisms to inhibit apoptosis, promote cell proliferation, and interfere with DNA repair, contributing to tumorigenesis. EBV’s lytic proteins, including BZLF1 and BPLF1, further disrupt cellular processes to favor oncogenesis. Similarly, KSHV, a causative agent of Kaposi’s Sarcoma and lymphoproliferative disorders, has a latency-associated nuclear antigen (LANA) and other latency proteins that manipulate ubiquitin pathways to degrade tumor suppressors, stabilize oncogenic proteins, and evade immune responses. KSHV’s lytic cycle proteins, such as RTA and Orf64, also use ubiquitin-mediated strategies to impair immune functions and promote oncogenesis. This review explores the ubiquitin-mediated interactions of EBV and KSHV proteins, elucidating their roles in viral oncogenesis. Understanding these mechanisms offers insights into the similarities between the viruses, as well as provoking thought about potential therapeutic targets for herpesvirus-associated cancers.
... EBNA3C stabilizes CCND2 to regulate cell cycle progression [126]. EBNA3C also stabilizes CCND1 through inhibition of its polyubiquitination and EBNA3C enhances the kinase activity of Cyclin D1/CDK6 [127] ( Figure 1). EBNA3C amino acids 130-160 bind to two different sites on CCND1. ...
Epstein–Barr virus (EBV) is the first human DNA tumor virus identified from African Burkitt’s lymphoma cells. EBV causes ~200,000 various cancers world-wide each year. EBV-associated cancers express latent EBV proteins, EBV nuclear antigens (EBNAs), and latent membrane proteins (LMPs). EBNA1 tethers EBV episomes to the chromosome during mitosis to ensure episomes are divided evenly between daughter cells. EBNA2 is the major EBV latency transcription activator. It activates the expression of other EBNAs and LMPs. It also activates MYC through enhancers 400–500 kb upstream to provide proliferation signals. EBNALP co-activates with EBNA2. EBNA3A/C represses CDKN2A to prevent senescence. LMP1 activates NF-κB to prevent apoptosis. The coordinated activity of EBV proteins in the nucleus allows efficient transformation of primary resting B lymphocytes into immortalized lymphoblastoid cell lines in vitro.
... These intracellular pathogens have evolved impressive strategies to modulate the kinase activity of the Cyclin/CDK complex by interacting with the individual subunits of the heterodimer or altering the activity of CKIs. For instance, the EBV nuclear antigen-3C (E3C) interacts with the D-type cyclins D1 and D2 (Saha et al., 2011;Pei et al., 2018). E3C can form stable complexes with G 1 phase cyclins-D1 and D2/CDK-6 heterodimer [ Fig. 2a] (Saha et al., 2011;Pei et al., 2018). ...
... For instance, the EBV nuclear antigen-3C (E3C) interacts with the D-type cyclins D1 and D2 (Saha et al., 2011;Pei et al., 2018). E3C can form stable complexes with G 1 phase cyclins-D1 and D2/CDK-6 heterodimer [ Fig. 2a] (Saha et al., 2011;Pei et al., 2018). By upregulating the expression of D-type cyclin, EBV can deregulate the activities of the G 1 phase. ...
... Furthermore, an in-vitro study revealed that the N-terminal amino acids (130-159) of E3C are responsible for binding with Cyclin A and restricting the p27 KIP1 -mediated inhibition of Cyclin A/CDK-2 kinase activity (Tursiella et al., 2014). At the same time, C-terminal domain amino acids (957-990) might be playing a role in stabilizing the elements of this complex [ Fig. 2a] Saha et al., 2011). E3C might serve as a bridge between SCF Skp2 and p27 KIP1 , resulting in the degradation of p27 KIP1 , thereby relieving its inhibitory effect on the Cyclin A/CDK-2 complex (Jason S. Knight Jason et al., 2005). ...
The Epstein-Barr virus is a well-known cell cycle modulator. To establish successful infection in the host, EBV alters the cell cycle at multiple steps via antigens such as EBNAs, LMPs, and certain other EBV-encoded transcripts. Interestingly, several recent studies have indicated the possibility of EBV's neurotrophic potential. However, the effects and outcomes of EBV infection in the CNS are under-explored. Additionally, more and more epidemiological evidence implicates the cell-cycle dysregulation in neurodegeneration. Numerous hypotheses describe the triggers that force post-mitotic neurons to re-enter the cell cycle are prevalent. Apart from the known genetic and epigenetic factors responsible, several reports have shown the association of microbial infections with neurodegenerative pathology. Although, studies implicating the herpesvirus family members in neurodegeneration exist, the involvement of Epstein-Barr virus (EBV), in particular, is under-evaluated. Interestingly, a few clinical studies have reported patients of AD or PD to be seropositive for EBV. Based on the findings mentioned above, in this review, we propose that EBV infection in neurons could drive it towards neurodegeneration through dysregulation of cell-cycle events and induction of apoptosis.
... Frequent dysregulation of Bcl6 expression is involved in various B ce Furthermore, previous studies showed that EBNA3C can induce the degradation of Bcl6 protein through the ubiquitin-proteasome-dependent signaling pathway, further promoting cell proliferation, and the cell cycle by targeting Bcl2 and cyclin D1 [21]. EBNA3C directly interacts with cyclin D1 and inhibits its ubiquitination [22]. EBNA3C also stabilizes cyclin D2 by suppressing its ubiquitin-dependent degradation to facilitate cell proliferation [23]. ...
Simple Summary
Epstein–Barr virus (EBV) is the first discovered human tumor virus, which contributes to the oncogenesis of many human cancers. The ubiquitin–proteasome system is a key player during EBV-mediated oncogenesis and has been developed as a crucial therapeutic target for treatment. In this review, we briefly describe how EBV antigens can modulate the ubiquitin–proteasome system for targeted protein degradation and how they are regulated in the EBV life cycle to mediate oncogenesis. Additionally, the developed proteasome inhibitors are discussed for the treatment of EBV-associated cancers.
Abstract
Deregulation of the ubiquitin–proteasome system (UPS) plays a critical role in the development of numerous human cancers. Epstein–Barr virus (EBV), the first known human tumor virus, has evolved distinct molecular mechanisms to manipulate the ubiquitin–proteasome system, facilitate its successful infection, and drive opportunistic cancers. The interactions of EBV antigens with the ubiquitin–proteasome system can lead to oncogenesis through the targeting of cellular factors involved in proliferation. Recent studies highlight the central role of the ubiquitin–proteasome system in EBV infection. This review will summarize the versatile strategies in EBV-mediated oncogenesis that contribute to the development of specific therapeutic approaches to treat EBV-associated malignancies.
... Knockdown of Gli2 reversed the cancer-promoting effect of circcd151. cyclin d1 is a key protein regulating G 1 /S phase transformation, which can cause dna replication and division (50,51). Studies have shown that the expression of cyclind1 and Bax decreases and the expression of Bcl-2 increases following Gli2 gene silencing (52,53). ...
To investigate the changes of circular (circ)RNA circCD151 expression in lung cancer tissues and cells and its effects on proliferation, migration and invasion of lung cancer cells. The relative expression levels of circCD151 in lung cancer tissues and lung cancer cells (A549 and NCI‑H292) were determined by reverse transcription‑quantitative PCR. The effects of silencing or upregulation of circCD151 on the activity and clonal forming ability of A549 and NCI‑H292 cells were detected by CCK‑8 and cloning formation experiments. Transwell invasion assay detected the effects of silencing or upregulation of circCD151 on the migration and invasion ability of A549 and NCI‑H292 cells. The regulatory effect of circCD151 on miR‑30d‑5p was detected by dual luciferase reporter gene. The relative expression level of circCD151 in lung cancer tissues was significantly higher compared with that in adjacent tissues. The relative expression level of circCD151 in A549 and NCI‑H292 cells was significantly higher compared with that in human lung epithelial cells. In A549 and NCI‑H292 cells, silencing circCD151 decreased cell activity and clonal formation ability and invasion ability was also significantly decreased. circCD151 was upregulated in A549 and NCI‑H292 cells and the activity and clonal formation ability of A549 and NCI‑H292 cells were significantly increased and the invasion ability was also significantly increased. Double luciferase reporter assay confirmed the ceRNA regulatory mechanism of circCD151/miR‑30d‑5p/GLI2. In the present study, in vivo and in vitro functional studies demonstrated that circCD151 may promote the proliferation, invasion and cell stemness of lung cancer cells. Further molecular mechanism studies demonstrated that circCD151 could promote the malignant proliferation of lung adenocarcinoma by targeting miR‑30d‑5p and upregulating GLI2 expression. From the perspective of circRNA, the present study will provide new clues to the pathogenesis and prognostic judgment of lung adenocarcinoma and provide a new target for clinical treatment.
... Flow cytometry suggested that apatinib was involved in the inhibition of G1/S cell cycle transition in GBM cells (Fig. 5B). Cyclin D1 is an important marker of G1 phase arrest in the cell cycle 31 . Western blotting revealed that the expression (see figure on previous page) Fig. 3 NDUFA4L2 knockdown induces apoptosis, which is further enhanced by autophagy inhibitor treatment in vitro and vivo. ...
NADH dehydrogenase [ubiquinone] 1 alpha subcomplex, 4-like 2 (NDUFA4L2) is a subunit of Complex I of the mitochondrial respiratory chain, which is important in metabolic reprogramming and oxidative stress in multiple cancers. However, the biological role and molecular regulation of NDUFA4L2 in glioblastoma (GBM) are poorly understood. Here, we found that NDUFA4L2 was significantly upregulated in GBM; the elevated levels were correlated with reduced patient survival. Gene knockdown of NDUFA4L2 inhibited tumor cell proliferation and enhanced apoptosis, while tumor cells initiated protective mitophagy in vitro and in vivo. We used lentivirus to reduce expression levels of NDUFA4L2 protein in GBM cells exposed to mitophagy blockers, which led to a significant enhancement of tumor cell apoptosis in vitro and inhibited the development of xenografted tumors in vivo. In contrast to other tumor types, NDUFA4L2 expression in GBM may not be directly regulated by hypoxia-inducible factor (HIF)-1α, because HIF-1α inhibitors failed to inhibit NDUFA4L2 in GBM. Apatinib was able to effectively target NDUFA4L2 in GBM, presenting an alternative to the use of lentiviruses, which currently cannot be used in humans. Taken together, our data suggest the use of NDUFA4L2 as a potential therapeutic target in GBM and demonstrate a practical treatment approach.
... In addition, a prominent role of EBNA3C is pointed in this context as it can interact and transcriptionally regulate a wide array of cellular and viral transcriptional factors (153). For instance, EBNA3C N-terminal region was shown to complex with the N-terminal pRb binding domain and C-terminal domain of cyclin D1, which not only stabilizes cyclin D1 through the inhibition of its ubiquitin-mediated proteasomal degradation, but also enhances the functional kinase activity of cyclin D1/CDK6, thus facilitating the G1-S transition (154). Repression of p53 transcriptional activity and sparing p53-induced apoptosis in osteosarcoma cells was mediated by EBNA3C direct interaction of the latter N-terminal domain with p53 C-terminal DNA-binding and tetramerization domain (155). ...
Tumors are renowned as intricate systems that harbor heterogeneous cancer cells with distinctly diverse molecular signatures, sizes and genomic contents. Among those various genomic clonal populations within the complex tumoral architecture are the polyploid giant cancer cells (PGCC). Although described for over a century, PGCC are increasingly being recognized for their prominent role in tumorigenesis, metastasis, therapy resistance and tumor repopulation after therapy. A shared characteristic among all tumors triggered by oncoviruses is the presence of polyploidy. Those include Human Papillomaviruses (HPV), Epstein Barr Virus (EBV), Hepatitis B and C viruses (HBV and HCV, respectively), Human T-cell lymphotropic virus-1 (HTLV-1), Kaposi's sarcoma herpesvirus (KSHV) and Merkel polyomavirus (MCPyV). Distinct viral proteins, for instance Tax for HTLV-1 or HBx for HBV have demonstrated their etiologic role in favoring the appearance of PGCC. Different intriguing biological mechanisms employed by oncogenic viruses, in addition to viruses with high oncogenic potential such as human cytomegalovirus, could support the generation of PGCC, including induction of endoreplication, inactivation of tumor suppressors, development of hypoxia, activation of cellular senescence and others. Interestingly, chemoresistance and radioresistance have been reported in the context of oncovirus-induced cancers, for example KSHV and EBV-associated lymphomas and high-risk HPV-related cervical cancer. This points toward a potential linkage between the previously mentioned players and highlights PGCC as keystone cancer cells in virally-induced tumors. Subsequently, although new therapeutic approaches are actively needed to fight PGCC, attention should also be drawn to reveal the relationship between PGCC and oncoviruses, with the ultimate goal of establishing effective therapeutic platforms for treatment of virus-associated cancers. This review discusses the presence of PGCCs in tumors induced by oncoviruses, biological mechanisms potentially favoring their appearance, as well as their consequent implication at the clinical and therapeutic level.
... Cyclin D and cyclindependent kinase (CDK) have been identified as potential therapeutic targets in cancers [19]. The EBV essential antigen EBNA3C facilitates G1/S transition and cell proliferation by stabilizing Cyclin D1 and Cyclin D2 proteins in EBV-transformed cells [20,21]. LMP1 can also induce Cyclin D2 ...
... Cyclin D and cyclin-dependent kinase (CDK) have been identified as potential therapeutic targets in cancers [19]. The EBV essential antigen EBNA3C facilitates G1/S transition and cell proliferation by stabilizing Cyclin D1 and Cyclin D2 proteins in EBV-transformed cells [20,21]. LMP1 can also induce Cyclin D2 expression to mediate uncontrolled cell proliferation [22]. ...
Simple Summary
Epstein-Barr virus (EBV) is the first-discovered and important human tumor virus. It infects more than 90% of human population and induces various lymphomas. Development of specific targeted therapies is very critical for treatment of EBV-induced lymphomas, but it remains a great challenge. In this review, we introduced the current progress of EBV-specific therapies and the promising approaches that can be developed as novel targeted therapies, which involve protective or therapeutic strategies to target these lymphomas on different levels. This work will provide new insights into the development of new targeted therapies against EBV-associated lymphomas.
Abstract
The Epstein-Barr virus (EBV) is the first human tumor virus identified that can transform quiescent B lymphocytes into lymphoblastoid cell lines (LCLs) in vitro. EBV can establish asymptomatic life-long persistence and is associated with multiple human malignancies, including non-Hodgkin lymphoma and Hodgkin lymphoma, as well as infectious mononucleosis. Although EBV-associated lymphomagenesis has been investigated for over 50 years, viral-mediated transformation is not completely understood, and the development of EBV-specific therapeutic strategies to treat the associated cancers is still a major challenge. However, the rapid development of several novel therapies offers exciting possibilities to target EBV-induced lymphomas. This review highlights targeted therapies with potential for treating EBV-associated lymphomas, including small molecule inhibitors, immunotherapy, cell therapy, preventative and therapeutic vaccines, and other potent approaches, which are novel strategies for controlling, preventing, and treating these viral-induced malignances.
... Mdm2, Cyclin D1, c-Myc, Pim1) or enhance degradation of tumor suppressor proteins (viz. p53, p27 Kip1 , pRb, p21 CIP1 ) [27,28,29,30,31,32]. In addition, EBNA3C is poly-ubiquitinated at the N-terminal region and interacts with the C8/α7 subunit of the 20S proteasome [28,33]. ...
... Earlier, we have demonstrated that EBNA3C expression increases basal level of K63-linked polyubiquitination, which further increases in absence of growth promoting signals [36]. Additionally, EBNA3C was shown to recruit UPS to regulate turn-over of many important cell oncoproteins and tumor suppressors [27,28,29,30,31,74,75,76]. Initially Knight et al. demonstrated the poly-ubiquitination on the N-terminal domain of EBNA3C [28]. ...
... Myc-, flag-, GFP-and RFP-tagged EBNA3C constructs in pA3M, pA3F, pEGFP-C1 and pDsRED-Monomer-N1 vectors, respectively were previously described [27,29,36]. Myc-tagged EBNA1 expressing construct in pA3M was described earlier [90]. ...
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 K63-linked 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 N-terminal 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.
... In Vitro cell transformation, up-regulate chemokines, (White et al., 2012) EBNA3C Co-activates ENBA2, Interact with cell cycle regulation, apoptosis and tumor suppressor proteins (Lin et al., 2002;Piovan et al., 2005;Saha et al, 2011aSaha et al, , 2011bSaha and Robertson, 2011) EBNA5 Helps in B cell transformation, Act as a transcriptional activator (Harada and Kieff, 1997;Mannick et al., 1991) LMP1 Mimic CD40 signaling, Act as an oncogene. (F Hu et al., 1993;Izumi et al., 1997;Mancao et al., 2005;Mosialos et al., 1995;Wang et al., 1985) LMP2A ...
p53, p63, and p73, the members of the p53 family of proteins, are structurally similar proteins that play central roles regulating cell cycle and apoptotic cell death. Alternative splicing at the carboxyl terminus and the utilization of different promoters further categorizes these proteins as having different isoforms for each. Among such isoforms, TA and ΔN versions of each protein serve as the pro and the anti-apoptotic proteins, respectively. Changes in the expression patterns of these isoforms are noted in many human cancers. Proteins of certain human herpesviruses, like Kaposi's sarcoma-associated herpesvirus (KSHV) and Epstein-Barr virus (EBV), interact with p53 family members and alter their expressions in many malignancies. Upon infections in the B cells and epithelial cells, EBV expresses different lytic or latent proteins during viral replication and latency respectively to preserve viral copy number, chromosomal integrity and viral persistence inside the host. In this review, we have surveyed and summarised the interactions of EBV gene products, known so far, with the p53 family proteins. The interactions between P53 and EBV oncoproteins are observed in stomach cancer, non-Hodgkin's lymphoma (NHL) of the head and neck, Nasopharyngeal Cancer (NPC), Gastric carcinoma (GC) and Burkitt's lymphoma (BL). EBV latent protein EBNA1, EBNA3C, LMP-1, and lytic proteins BZLF-1 can alter p53 expressions in many cancer cell lines. Interactions of p63 with EBNA-1, 2, 5, LMP-2A and BARF-1 have also been investigated in several cancers. Similarly, associations of p73 isoform with EBV latent proteins EBNA3C and LMP-1 have been reported. Methylation and single nucleotide polymorphisms in p53 have also been found to be correlated with EBV infection. Therefore, interactions and altered expression strategies of the isoforms of p53 family proteins in EBV associated cancers propose an important field for further molecular research.
