Tathagata Choudhuri - Academia.edu (original) (raw)
Papers by Tathagata Choudhuri
Oncology Research, Jul 1, 2011
Frontiers in Molecular Biosciences, Aug 2, 2023
As a part of viral cancer evolution, KSHV-infected human endothelial cells exert a unique transcr... more As a part of viral cancer evolution, KSHV-infected human endothelial cells exert a unique transcriptional program via upregulated mTORC1 signaling. This event makes them sensitive to mTOR inhibitors. Master transcriptional regulator PTEN acts as the prime regulator of mTOR and determining factor for mTOR inhibitory drug resistance and sensitivity. PTEN is posttranslationally modified in KSHV-associated cell lines and infected tissues. Our current study is an attempt to understand the functional role of upstream modulator PTEN in determining the sensitivity of mTOR inhibitors against KSHV-infected cells in an in vitro stress-responsive model. Our analysis shows that, despite phosphorylation, endogenous levels of intact PTEN in different KSHV-infected cells compared to normal and non-infected cells are quite high. Genetic overexpression of intact PTEN showed functional integrity of this gene in the infected cells in terms of induction of a synchronized cell death process via cell cycle regulation and mitochondria-mediated apoptosis. PTEN overexpression enhanced the mTOR inhibitory drug activity, the silencing of which hampers the process against KSHV-infected cells. Additionally, we have shown that endogenous PTEN acts as a stress balancer molecule inside KSHV-infected cells and can induce stresssensitized death program post mTOR inhibitor treatment, lined up in the ATM-chk2-p53 axis. Moreover, autophagic regulation was found as a major regulator in mTOR inhibitor-induced PTEN-mediated death axis from our study. The current work critically intersected the PTEN-mediated stress balancing mechanism where autophagy has been utilized as a part of the KSHV stress management system and is specifically fitted and switched toward autophagy-mediated apoptosis directing toward a therapeutic perspective.
Toxicology and Applied Pharmacology, Mar 15, 2014
Cigarette smoking is a key factor for the development and progression of different cancers includ... more Cigarette smoking is a key factor for the development and progression of different cancers including mammary tumor in women. Resveratrol (Res) is a promising natural chemotherapeutic agent that regulates many cellular targets including p21, a cip/kip family of cyclin kinase inhibitors involved in DNA damage-induced cell cycle arrest and blocking of DNA replication and repair. We have recently shown that cigarette smoke condensate (CSC) prepared from commercially available Indian cigarette can cause neoplastic transformation of normal breast epithelial MCF-10A cell. Here we studied the mechanism of Res mediated apoptosis in CSC transformed (MCF-10A-Tr) cells in vitro and in vivo. Res mediated apoptosis in MCF-10A-Tr cells was a p21 dependent event. It increased the p21 protein expression in MCF-10A-Tr cells and MCF-10A-Tr cells-mediated tumors in xenograft mice. Res treatment reduced the tumor size(s) and expression of anti-apoptotic proteins (e.g. PI3K, AKT, NFκB) in solid tumor. The expressions of cell cycle regulatory (Cyclins, CDC-2, CDC-6, etc.), BER associated (Pol-β, Pol-δ, Pol-ε, Pol-η, RPA, Fen-1, DNA-Ligase-I, etc.) proteins and LP-BER activity decreased in MCF-10A-Tr cells but remain significantly unaltered in isogenic p21 null MCF-10A-Tr cells after Res treatment. Interestingly, no significant changes were noted in SP-BER activity in both the cell lines after Res exposure. Finally, it was observed that increased p21 blocks the LP-BER in MCF-10A-Tr cells by increasing its interaction with PCNA via competing with Fen-1 after Res treatment. Thus, Res caused apoptosis in CSC-induced cancer cells by reduction of LP-BER activity and this phenomenon largely depends on p21.
Journal of Virology, Jul 1, 2006
Oncology Research, Nov 15, 2013
Nanomedicine, Aug 1, 2013
Current Bioactive Compounds, Jan 16, 2024
Scientific Reports, Dec 11, 2023
The TNM staging system is currently used to detect cancer stages. Regardless, a small proportion ... more The TNM staging system is currently used to detect cancer stages. Regardless, a small proportion of cancer patients recur even after therapy, suggesting more specific molecular tools are required to justify the stage-specific detection and prompt cancer diagnosis. Thus, we aimed to explore the blood-based DNA methylation signature of metastatic nasopharyngeal carcinoma (NPC) to establish a holistic methylation biomarker panel. For the identification of methylation signature, the EPIC BeadChip-based array was performed. Comparative analysis for identifying unique probes, validation, and functional studies was investigated by analyzing GEO and TCGA datasets. We observed 4093 differentially methylated probes (DMPs), 1232 hydroxymethylated probes, and 25 CpG islands. Gene expression study revealed both upregulated and downregulated genes. Correlation analysis suggested a positive (with a positive r, p ≤ 0.05) and negative (with a negative r, p ≤ 0.05) association with different cancers. TFBS analysis exhibited the binding site for many TFs. Furthermore, gene enrichment analysis indicated the involvement of those identified genes in biological pathways. However, blood-based DNA methylation data uncovered a distinct DNA methylation pattern, which might have an additive role in NPC progression by altering the TFs binding. Moreover, based on tissuespecificity, a variation of correlation between methylation and gene expression was noted in different cancers. Nasopharyngeal carcinoma (NPC) is one of the predominant malignancies in South Asian continents, primarily in southern China, Indonesia, and India 1. According to the global cancer repository report published by GLO-BOCAN in 2020 (https:// gco. iarc. fr/), NPC ranked 22nd based on occurrence. Among the in-vogue treatment regimens, radiotherapy and parallel chemotherapy increase NPC patients' survival. To date, identifying NPC at an initial stage is challenging because the symptoms of this cancer resemble other, more common conditions, which creates confusion for clinicians to diagnose. It is also hard to examine the nasopharynx. Sometimes, the submucosal lesions spread silently with a standard appearance during clinical tests. Thus, many NPC patients appear in clinics with advanced stages, resulting in a poor prognosis 2. So far, the TNM (tumor-node-metastasis) staging technique is a decisive parameter in providing analytical information and directing treatment choices for cancers, including NPC. To date, this model is not enough to determine the best personalized treatment. About 20-30% of NPC patients with the same stages receiving similar treatment show local relapse or distal metastasis 3-5 , pointing out that molecular subclassification may be clinically appropriate, but more accurate molecular tools are a prerequisite that can stratify patients concerning prognosis and response to therapy. Since NPC is diversely categorized into four subtypes based on histological character and ethnicity-specific occurrence, there is very little knowledge available for NPC's prognostic biomarkers to predict and improve patient outcomes. The development of malignancy or its distribution is a complex phenomenon comprising many factors, which may differ uniquely from one cancer to another. Cumulative evidence suggests that the tumors' molecular characteristics add predictive strength in developing molecular biomarkers. DNA methylation at the 5ʹ cytosine
Organic and Biomolecular Chemistry, 2022
1-Butane sulfonic acid-3-methylimidazolium tosylate, [BSMIM]OTs, is a remarkable catalyst for the... more 1-Butane sulfonic acid-3-methylimidazolium tosylate, [BSMIM]OTs, is a remarkable catalyst for the cascade synthesis of coumarin-functionalized indole derivatives via a tandem cyclization reaction of aniline and phenylglyoxal monohydrate.
Journal of Virology, Apr 1, 2007
Kaposi's sarcoma-associated herpesvirus (KSHV) persists as episomes in infected cells by circular... more Kaposi's sarcoma-associated herpesvirus (KSHV) persists as episomes in infected cells by circularizing at the terminal repeats (TRs). The KSHV episome carries multiple reiterated copies of the terminal repeat, and each copy is capable of supporting replication. Expression of the latency-associated nuclear antigen (LANA) is critical for the replication of TR-containing plasmids. A 32-bp sequence upstream of LANA binding site 1 (LBS1), referred to as RE (replication element), along with LANA binding sites 1 and 2 (RE-LBS1/2), is sufficient to support replication (
Virology, Jul 1, 2006
Epstein-Barr virus (EBV) is a lymphotrophic herpesvirus infecting most of the world's population.... more Epstein-Barr virus (EBV) is a lymphotrophic herpesvirus infecting most of the world's population. It is associated with a number of human lymphoid and epithelial tumors and lymphoproliferative diseases in immunocompromised patients. A subset of latent EBV antigens is required for immortalization of primary B-lymphocytes. The metastatic suppressor Nm23-H1 which is downregulated in human invasive breast carcinoma reduces the migration and metastatic activity of breast carcinoma cells when expressed from a heterologous promoter. Interestingly, the EBV nuclear antigen 3C (EBNA3C) reverses these activities of Nm23-H1. The alpha V integrins recognize a variety of ligands for signaling and are involved in cell migration and proliferation and also serve as major receptors for extracellular-matrix-mediated cell adhesion and migration. The goal of this study was to determine if Nm23-H1 and EBNA3C can modulate alpha V integrin expression and downstream activities. The results of our studies indicate that Nm23-H1 downregulates alpha V intregrin expression in a dose responsive manner. In contrast, EBNA3C can upregulate alpha V integrin expression. Furthermore, the study showed that the association of the Sp1 and GATA transcription factors with Nm23-H1 is required for modulation of the alpha V integrin activity. Thus, these results suggest a direct correlation between the alpha V integrin expression and the interaction of Nm23-H1 with EBNA3C.
Cell Host & Microbe, Aug 1, 2007
Members of the herpesviridae family including Kaposi's sarcoma-associated herpesvirus (KSHV) pers... more Members of the herpesviridae family including Kaposi's sarcoma-associated herpesvirus (KSHV) persist latently in their hosts and harbor their genomes as closed circular episomes. Propagation of the KSHV genome into new daughter cells requires replication of the episome once every cell division and is considered critically dependent on expression of the virus encoded latency-associated nuclear antigen (LANA). This study demonstrates a LANA-independent mechanism of KSHV latent DNA replication. A cis-acting DNA element within a discreet KSHV genomic region termed the long unique region (LUR) can initiate and support replication of plasmids lacking LANA-binding sequences or a eukaryotic replication origin. The human cellular replication machinery proteins ORC2 and MCM3 associated with the LUR element and depletion of cellular ORC2 abolished replication of the plasmids indicating that recruitment of the host cellular replication machinery is important for LUR-dependent replication. Thus, KSHV can initiate replication of its genome independent of any transacting viral factors.
Journal of Virology, Oct 1, 2007
Epstein-Barr virus (EBV) is a ubiquitous human herpesvirus associated with the development of bot... more Epstein-Barr virus (EBV) is a ubiquitous human herpesvirus associated with the development of both lymphoid and epithelial tumors. The EBV critical latent antigens EBNA1 and EBNA3C interact with Nm23-H1, a known suppressor of cell migration and tumor metastasis. This interaction is critical for the regulation of downstream cellular genes involved in tumorigenesis and cell migration. The significance of these interactions was determined in nude mice using cancer cells expressing both EBV antigens and Nm23-H1. The EBV antigens promoted the growth of transformed cells in vivo, but their expression was less critical during the later stage of tumor development. The expression of Nm23-H1 affected the growth of cancer cells and suppressed their metastatic potential. This effect was effectively rescued by the expression of both EBV antigens. Interestingly, the prometastatic potential of EBNA3C was greater than that of EBNA1, which triggered a dramatic immune response, as indicated by increased spleen size and development of ascites in the mice. These studies now bridge the expression of the EBV antigens with tumorigenesis and metastasis and widen the range of potential targets for development of therapies for EBV-associated malignancies.
Journal of Virology, Feb 1, 2006
Previous studies have demonstrated the interaction between the Epstein-Barr virus (EBV) nuclear a... more Previous studies have demonstrated the interaction between the Epstein-Barr virus (EBV) nuclear antigen 3C (EBNA3C) and the metastatic suppressor Nm23-H1 both in vitro and in vivo (C. Subramanian, M. A. Cotter II, and E. S. Robertson, Nat. Med. 7:350-355, 2001). EBNA3C can reverse the ability of Nm23-H1 to suppress migration of Burkitt's lymphoma and breast carcinoma cell lines in vitro. EBNA3C contributes to EBVassociated human cancers by regulating transcription of a number of cellular and viral promoters and by targeting and altering the transcription activities of the metastasis suppressor Nm23-H1. Cyclo-oxygenase-2 (COX-2), an inducible enzyme important in inflammation, is overexpressed in a variety of cancers and can influence cell migration. In this report we show that Nm23-H1 and EBNA3C can modulate expression of COX-2 in the context of EBV infection and transformation. The levels of COX-2 were consistently higher in EBVpositive cells than in EBV-negative cells. Additionally, we show that Nm23-H1 can upregulate the COX-2 promoter element in luciferase reporter assays, whereas EBNA3C alone did not affect the level of response but clearly contributed to an additive increase when coexpressed with Nm23-H1. The downstream effect of COX-2 expression was also evaluated and showed that prostaglandin E 2 levels increased with Nm23-H1 and that there was some level of cooperativity in the presence of EBNA3C. The majority of this response was mediated through the cyclic AMP response element and NF-B sites. These studies suggest a potential role for COX-2 in EBV-associated human cancers.
Journal of Virology, Jun 15, 2007
Barr virus (EBV) infects most of the human population and persists in B lymphocytes for the lifet... more Barr virus (EBV) infects most of the human population and persists in B lymphocytes for the lifetime of the host. The establishment of latent infection by EBV requires the expression of a unique repertoire of genes. The product of one of these viral genes, the EBV nuclear antigen 3C (EBNA3C), is essential for the growth transformation of primary B lymphocytes in vitro and can regulate the transcription of a number of viral and cellular genes important for the immortalization process. This study demonstrates an associated function of EBNA3C which involves the disruption of the G 2 /M cell cycle checkpoint. We show that EBNA3Cexpressing lymphoblastoid cell lines treated with the drug nocodazole, which is known to block cells at the G 2 /M transition, did not show a G 2 /M-specific checkpoint arrest. Analyses of the cell cycles of cells expressing EBNA3C demonstrated that the expression of this essential EBV nuclear antigen is capable of releasing the G 2 /M checkpoint arrest induced by nocodazole. This G 2 /M arrest in response to nocodazole was also abolished by caffeine, suggesting an involvement of the ATM/ATR signaling pathway in the regulation of this cell cycle checkpoint. Importantly, we show that the direct interaction of EBNA3C with Chk2, the ATM/ATR signaling effector, is responsible for the release of this nocodazole-induced G 2 /M arrest and that this interaction leads to the serine 216 phosphorylation of Cdc25c, which is sequestered in the cytoplasm by 14-3-3. Overall, our data suggest that EBNA3C can directly regulate the G 2 /M component of the host cell cycle machinery, allowing for the release of the checkpoint block.
Journal of Virology, 2021
In the EBNA3C blot, the last band of the left subpanel and first band of the right subpanel are t... more In the EBNA3C blot, the last band of the left subpanel and first band of the right subpanel are the same band obtained in the same experiment. This band is presented as data from a single experiment in the two adjacent subpanels for better visualization and simplicity. Page 1327, Fig. 6B: Due to an error in figure assembly, the second lane is an inadvertent duplicate of the fifth lane. We have replaced the image using the correct original data. The lane between the currently labeled lane 4 and lane 5 was intentionally left blank. Figure 6B should appear as shown below. Correction of these errors does not affect the validity of the research or the conclusions that we have drawn.
Virology, 2014
The p73 protein has structural and functional homology with the tumor suppressor p53, which plays... more The p73 protein has structural and functional homology with the tumor suppressor p53, which plays an important role in cell cycle regulation, apoptosis, and DNA repair. The p73 locus encodes both a tumor suppressor (TAp73) and a putative oncogene (ΔNp73). p73 May play a significant role in p53-deficient lymphomas infected with Epstein-Barr virus (EBV). EBV produces an asymptomatic infection in the majority of the global population, but it is associated with several human B-cell malignancies. The EBV-encoded Epstein-Barr virus nuclear antigen 3C (EBNA3C) is thought to disrupt the cell cycle checkpoint by interacting directly with p53 family proteins. Doxorubicin, a commonly used chemotherapeutic agent, induces apoptosis through p53 and p73 signaling such that the lowΔNp73 level promotes the p73-mediated intrinsic pathway of apoptosis. In this report, we investigated the mechanism by which EBV infection counters p73α-induced apoptosis through EBNA3C.
Frontiers in Molecular Biosciences
As a part of viral cancer evolution, KSHV-infected human endothelial cells exert a unique transcr... more As a part of viral cancer evolution, KSHV-infected human endothelial cells exert a unique transcriptional program via upregulated mTORC1 signaling. This event makes them sensitive to mTOR inhibitors. Master transcriptional regulator PTEN acts as the prime regulator of mTOR and determining factor for mTOR inhibitory drug resistance and sensitivity. PTEN is post-translationally modified in KSHV-associated cell lines and infected tissues. Our current study is an attempt to understand the functional role of upstream modulator PTEN in determining the sensitivity of mTOR inhibitors against KSHV-infected cells in an in vitro stress-responsive model. Our analysis shows that, despite phosphorylation, endogenous levels of intact PTEN in different KSHV-infected cells compared to normal and non-infected cells are quite high. Genetic overexpression of intact PTEN showed functional integrity of this gene in the infected cells in terms of induction of a synchronized cell death process via cell cyc...
Oncology Research, Jul 1, 2011
Frontiers in Molecular Biosciences, Aug 2, 2023
As a part of viral cancer evolution, KSHV-infected human endothelial cells exert a unique transcr... more As a part of viral cancer evolution, KSHV-infected human endothelial cells exert a unique transcriptional program via upregulated mTORC1 signaling. This event makes them sensitive to mTOR inhibitors. Master transcriptional regulator PTEN acts as the prime regulator of mTOR and determining factor for mTOR inhibitory drug resistance and sensitivity. PTEN is posttranslationally modified in KSHV-associated cell lines and infected tissues. Our current study is an attempt to understand the functional role of upstream modulator PTEN in determining the sensitivity of mTOR inhibitors against KSHV-infected cells in an in vitro stress-responsive model. Our analysis shows that, despite phosphorylation, endogenous levels of intact PTEN in different KSHV-infected cells compared to normal and non-infected cells are quite high. Genetic overexpression of intact PTEN showed functional integrity of this gene in the infected cells in terms of induction of a synchronized cell death process via cell cycle regulation and mitochondria-mediated apoptosis. PTEN overexpression enhanced the mTOR inhibitory drug activity, the silencing of which hampers the process against KSHV-infected cells. Additionally, we have shown that endogenous PTEN acts as a stress balancer molecule inside KSHV-infected cells and can induce stresssensitized death program post mTOR inhibitor treatment, lined up in the ATM-chk2-p53 axis. Moreover, autophagic regulation was found as a major regulator in mTOR inhibitor-induced PTEN-mediated death axis from our study. The current work critically intersected the PTEN-mediated stress balancing mechanism where autophagy has been utilized as a part of the KSHV stress management system and is specifically fitted and switched toward autophagy-mediated apoptosis directing toward a therapeutic perspective.
Toxicology and Applied Pharmacology, Mar 15, 2014
Cigarette smoking is a key factor for the development and progression of different cancers includ... more Cigarette smoking is a key factor for the development and progression of different cancers including mammary tumor in women. Resveratrol (Res) is a promising natural chemotherapeutic agent that regulates many cellular targets including p21, a cip/kip family of cyclin kinase inhibitors involved in DNA damage-induced cell cycle arrest and blocking of DNA replication and repair. We have recently shown that cigarette smoke condensate (CSC) prepared from commercially available Indian cigarette can cause neoplastic transformation of normal breast epithelial MCF-10A cell. Here we studied the mechanism of Res mediated apoptosis in CSC transformed (MCF-10A-Tr) cells in vitro and in vivo. Res mediated apoptosis in MCF-10A-Tr cells was a p21 dependent event. It increased the p21 protein expression in MCF-10A-Tr cells and MCF-10A-Tr cells-mediated tumors in xenograft mice. Res treatment reduced the tumor size(s) and expression of anti-apoptotic proteins (e.g. PI3K, AKT, NFκB) in solid tumor. The expressions of cell cycle regulatory (Cyclins, CDC-2, CDC-6, etc.), BER associated (Pol-β, Pol-δ, Pol-ε, Pol-η, RPA, Fen-1, DNA-Ligase-I, etc.) proteins and LP-BER activity decreased in MCF-10A-Tr cells but remain significantly unaltered in isogenic p21 null MCF-10A-Tr cells after Res treatment. Interestingly, no significant changes were noted in SP-BER activity in both the cell lines after Res exposure. Finally, it was observed that increased p21 blocks the LP-BER in MCF-10A-Tr cells by increasing its interaction with PCNA via competing with Fen-1 after Res treatment. Thus, Res caused apoptosis in CSC-induced cancer cells by reduction of LP-BER activity and this phenomenon largely depends on p21.
Journal of Virology, Jul 1, 2006
Oncology Research, Nov 15, 2013
Nanomedicine, Aug 1, 2013
Current Bioactive Compounds, Jan 16, 2024
Scientific Reports, Dec 11, 2023
The TNM staging system is currently used to detect cancer stages. Regardless, a small proportion ... more The TNM staging system is currently used to detect cancer stages. Regardless, a small proportion of cancer patients recur even after therapy, suggesting more specific molecular tools are required to justify the stage-specific detection and prompt cancer diagnosis. Thus, we aimed to explore the blood-based DNA methylation signature of metastatic nasopharyngeal carcinoma (NPC) to establish a holistic methylation biomarker panel. For the identification of methylation signature, the EPIC BeadChip-based array was performed. Comparative analysis for identifying unique probes, validation, and functional studies was investigated by analyzing GEO and TCGA datasets. We observed 4093 differentially methylated probes (DMPs), 1232 hydroxymethylated probes, and 25 CpG islands. Gene expression study revealed both upregulated and downregulated genes. Correlation analysis suggested a positive (with a positive r, p ≤ 0.05) and negative (with a negative r, p ≤ 0.05) association with different cancers. TFBS analysis exhibited the binding site for many TFs. Furthermore, gene enrichment analysis indicated the involvement of those identified genes in biological pathways. However, blood-based DNA methylation data uncovered a distinct DNA methylation pattern, which might have an additive role in NPC progression by altering the TFs binding. Moreover, based on tissuespecificity, a variation of correlation between methylation and gene expression was noted in different cancers. Nasopharyngeal carcinoma (NPC) is one of the predominant malignancies in South Asian continents, primarily in southern China, Indonesia, and India 1. According to the global cancer repository report published by GLO-BOCAN in 2020 (https:// gco. iarc. fr/), NPC ranked 22nd based on occurrence. Among the in-vogue treatment regimens, radiotherapy and parallel chemotherapy increase NPC patients' survival. To date, identifying NPC at an initial stage is challenging because the symptoms of this cancer resemble other, more common conditions, which creates confusion for clinicians to diagnose. It is also hard to examine the nasopharynx. Sometimes, the submucosal lesions spread silently with a standard appearance during clinical tests. Thus, many NPC patients appear in clinics with advanced stages, resulting in a poor prognosis 2. So far, the TNM (tumor-node-metastasis) staging technique is a decisive parameter in providing analytical information and directing treatment choices for cancers, including NPC. To date, this model is not enough to determine the best personalized treatment. About 20-30% of NPC patients with the same stages receiving similar treatment show local relapse or distal metastasis 3-5 , pointing out that molecular subclassification may be clinically appropriate, but more accurate molecular tools are a prerequisite that can stratify patients concerning prognosis and response to therapy. Since NPC is diversely categorized into four subtypes based on histological character and ethnicity-specific occurrence, there is very little knowledge available for NPC's prognostic biomarkers to predict and improve patient outcomes. The development of malignancy or its distribution is a complex phenomenon comprising many factors, which may differ uniquely from one cancer to another. Cumulative evidence suggests that the tumors' molecular characteristics add predictive strength in developing molecular biomarkers. DNA methylation at the 5ʹ cytosine
Organic and Biomolecular Chemistry, 2022
1-Butane sulfonic acid-3-methylimidazolium tosylate, [BSMIM]OTs, is a remarkable catalyst for the... more 1-Butane sulfonic acid-3-methylimidazolium tosylate, [BSMIM]OTs, is a remarkable catalyst for the cascade synthesis of coumarin-functionalized indole derivatives via a tandem cyclization reaction of aniline and phenylglyoxal monohydrate.
Journal of Virology, Apr 1, 2007
Kaposi's sarcoma-associated herpesvirus (KSHV) persists as episomes in infected cells by circular... more Kaposi's sarcoma-associated herpesvirus (KSHV) persists as episomes in infected cells by circularizing at the terminal repeats (TRs). The KSHV episome carries multiple reiterated copies of the terminal repeat, and each copy is capable of supporting replication. Expression of the latency-associated nuclear antigen (LANA) is critical for the replication of TR-containing plasmids. A 32-bp sequence upstream of LANA binding site 1 (LBS1), referred to as RE (replication element), along with LANA binding sites 1 and 2 (RE-LBS1/2), is sufficient to support replication (
Virology, Jul 1, 2006
Epstein-Barr virus (EBV) is a lymphotrophic herpesvirus infecting most of the world's population.... more Epstein-Barr virus (EBV) is a lymphotrophic herpesvirus infecting most of the world's population. It is associated with a number of human lymphoid and epithelial tumors and lymphoproliferative diseases in immunocompromised patients. A subset of latent EBV antigens is required for immortalization of primary B-lymphocytes. The metastatic suppressor Nm23-H1 which is downregulated in human invasive breast carcinoma reduces the migration and metastatic activity of breast carcinoma cells when expressed from a heterologous promoter. Interestingly, the EBV nuclear antigen 3C (EBNA3C) reverses these activities of Nm23-H1. The alpha V integrins recognize a variety of ligands for signaling and are involved in cell migration and proliferation and also serve as major receptors for extracellular-matrix-mediated cell adhesion and migration. The goal of this study was to determine if Nm23-H1 and EBNA3C can modulate alpha V integrin expression and downstream activities. The results of our studies indicate that Nm23-H1 downregulates alpha V intregrin expression in a dose responsive manner. In contrast, EBNA3C can upregulate alpha V integrin expression. Furthermore, the study showed that the association of the Sp1 and GATA transcription factors with Nm23-H1 is required for modulation of the alpha V integrin activity. Thus, these results suggest a direct correlation between the alpha V integrin expression and the interaction of Nm23-H1 with EBNA3C.
Cell Host & Microbe, Aug 1, 2007
Members of the herpesviridae family including Kaposi's sarcoma-associated herpesvirus (KSHV) pers... more Members of the herpesviridae family including Kaposi's sarcoma-associated herpesvirus (KSHV) persist latently in their hosts and harbor their genomes as closed circular episomes. Propagation of the KSHV genome into new daughter cells requires replication of the episome once every cell division and is considered critically dependent on expression of the virus encoded latency-associated nuclear antigen (LANA). This study demonstrates a LANA-independent mechanism of KSHV latent DNA replication. A cis-acting DNA element within a discreet KSHV genomic region termed the long unique region (LUR) can initiate and support replication of plasmids lacking LANA-binding sequences or a eukaryotic replication origin. The human cellular replication machinery proteins ORC2 and MCM3 associated with the LUR element and depletion of cellular ORC2 abolished replication of the plasmids indicating that recruitment of the host cellular replication machinery is important for LUR-dependent replication. Thus, KSHV can initiate replication of its genome independent of any transacting viral factors.
Journal of Virology, Oct 1, 2007
Epstein-Barr virus (EBV) is a ubiquitous human herpesvirus associated with the development of bot... more Epstein-Barr virus (EBV) is a ubiquitous human herpesvirus associated with the development of both lymphoid and epithelial tumors. The EBV critical latent antigens EBNA1 and EBNA3C interact with Nm23-H1, a known suppressor of cell migration and tumor metastasis. This interaction is critical for the regulation of downstream cellular genes involved in tumorigenesis and cell migration. The significance of these interactions was determined in nude mice using cancer cells expressing both EBV antigens and Nm23-H1. The EBV antigens promoted the growth of transformed cells in vivo, but their expression was less critical during the later stage of tumor development. The expression of Nm23-H1 affected the growth of cancer cells and suppressed their metastatic potential. This effect was effectively rescued by the expression of both EBV antigens. Interestingly, the prometastatic potential of EBNA3C was greater than that of EBNA1, which triggered a dramatic immune response, as indicated by increased spleen size and development of ascites in the mice. These studies now bridge the expression of the EBV antigens with tumorigenesis and metastasis and widen the range of potential targets for development of therapies for EBV-associated malignancies.
Journal of Virology, Feb 1, 2006
Previous studies have demonstrated the interaction between the Epstein-Barr virus (EBV) nuclear a... more Previous studies have demonstrated the interaction between the Epstein-Barr virus (EBV) nuclear antigen 3C (EBNA3C) and the metastatic suppressor Nm23-H1 both in vitro and in vivo (C. Subramanian, M. A. Cotter II, and E. S. Robertson, Nat. Med. 7:350-355, 2001). EBNA3C can reverse the ability of Nm23-H1 to suppress migration of Burkitt's lymphoma and breast carcinoma cell lines in vitro. EBNA3C contributes to EBVassociated human cancers by regulating transcription of a number of cellular and viral promoters and by targeting and altering the transcription activities of the metastasis suppressor Nm23-H1. Cyclo-oxygenase-2 (COX-2), an inducible enzyme important in inflammation, is overexpressed in a variety of cancers and can influence cell migration. In this report we show that Nm23-H1 and EBNA3C can modulate expression of COX-2 in the context of EBV infection and transformation. The levels of COX-2 were consistently higher in EBVpositive cells than in EBV-negative cells. Additionally, we show that Nm23-H1 can upregulate the COX-2 promoter element in luciferase reporter assays, whereas EBNA3C alone did not affect the level of response but clearly contributed to an additive increase when coexpressed with Nm23-H1. The downstream effect of COX-2 expression was also evaluated and showed that prostaglandin E 2 levels increased with Nm23-H1 and that there was some level of cooperativity in the presence of EBNA3C. The majority of this response was mediated through the cyclic AMP response element and NF-B sites. These studies suggest a potential role for COX-2 in EBV-associated human cancers.
Journal of Virology, Jun 15, 2007
Barr virus (EBV) infects most of the human population and persists in B lymphocytes for the lifet... more Barr virus (EBV) infects most of the human population and persists in B lymphocytes for the lifetime of the host. The establishment of latent infection by EBV requires the expression of a unique repertoire of genes. The product of one of these viral genes, the EBV nuclear antigen 3C (EBNA3C), is essential for the growth transformation of primary B lymphocytes in vitro and can regulate the transcription of a number of viral and cellular genes important for the immortalization process. This study demonstrates an associated function of EBNA3C which involves the disruption of the G 2 /M cell cycle checkpoint. We show that EBNA3Cexpressing lymphoblastoid cell lines treated with the drug nocodazole, which is known to block cells at the G 2 /M transition, did not show a G 2 /M-specific checkpoint arrest. Analyses of the cell cycles of cells expressing EBNA3C demonstrated that the expression of this essential EBV nuclear antigen is capable of releasing the G 2 /M checkpoint arrest induced by nocodazole. This G 2 /M arrest in response to nocodazole was also abolished by caffeine, suggesting an involvement of the ATM/ATR signaling pathway in the regulation of this cell cycle checkpoint. Importantly, we show that the direct interaction of EBNA3C with Chk2, the ATM/ATR signaling effector, is responsible for the release of this nocodazole-induced G 2 /M arrest and that this interaction leads to the serine 216 phosphorylation of Cdc25c, which is sequestered in the cytoplasm by 14-3-3. Overall, our data suggest that EBNA3C can directly regulate the G 2 /M component of the host cell cycle machinery, allowing for the release of the checkpoint block.
Journal of Virology, 2021
In the EBNA3C blot, the last band of the left subpanel and first band of the right subpanel are t... more In the EBNA3C blot, the last band of the left subpanel and first band of the right subpanel are the same band obtained in the same experiment. This band is presented as data from a single experiment in the two adjacent subpanels for better visualization and simplicity. Page 1327, Fig. 6B: Due to an error in figure assembly, the second lane is an inadvertent duplicate of the fifth lane. We have replaced the image using the correct original data. The lane between the currently labeled lane 4 and lane 5 was intentionally left blank. Figure 6B should appear as shown below. Correction of these errors does not affect the validity of the research or the conclusions that we have drawn.
Virology, 2014
The p73 protein has structural and functional homology with the tumor suppressor p53, which plays... more The p73 protein has structural and functional homology with the tumor suppressor p53, which plays an important role in cell cycle regulation, apoptosis, and DNA repair. The p73 locus encodes both a tumor suppressor (TAp73) and a putative oncogene (ΔNp73). p73 May play a significant role in p53-deficient lymphomas infected with Epstein-Barr virus (EBV). EBV produces an asymptomatic infection in the majority of the global population, but it is associated with several human B-cell malignancies. The EBV-encoded Epstein-Barr virus nuclear antigen 3C (EBNA3C) is thought to disrupt the cell cycle checkpoint by interacting directly with p53 family proteins. Doxorubicin, a commonly used chemotherapeutic agent, induces apoptosis through p53 and p73 signaling such that the lowΔNp73 level promotes the p73-mediated intrinsic pathway of apoptosis. In this report, we investigated the mechanism by which EBV infection counters p73α-induced apoptosis through EBNA3C.
Frontiers in Molecular Biosciences
As a part of viral cancer evolution, KSHV-infected human endothelial cells exert a unique transcr... more As a part of viral cancer evolution, KSHV-infected human endothelial cells exert a unique transcriptional program via upregulated mTORC1 signaling. This event makes them sensitive to mTOR inhibitors. Master transcriptional regulator PTEN acts as the prime regulator of mTOR and determining factor for mTOR inhibitory drug resistance and sensitivity. PTEN is post-translationally modified in KSHV-associated cell lines and infected tissues. Our current study is an attempt to understand the functional role of upstream modulator PTEN in determining the sensitivity of mTOR inhibitors against KSHV-infected cells in an in vitro stress-responsive model. Our analysis shows that, despite phosphorylation, endogenous levels of intact PTEN in different KSHV-infected cells compared to normal and non-infected cells are quite high. Genetic overexpression of intact PTEN showed functional integrity of this gene in the infected cells in terms of induction of a synchronized cell death process via cell cyc...