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Patrick S. Moore - One of the best experts on this subject based on the ideXlab platform.

  • The emergence of Kaposi's sarcoma-associated Herpesvirus (Human Herpesvirus 8).
    The New England journal of medicine, 2000
    Co-Authors: Patrick S. Moore
    Abstract:

    The concept of emerging “new” pathogens is somewhat misnamed, since these pathogens are usually old infections that have newly adapted to social and technological changes. Such is the case for Kaposi's sarcoma–associated Herpesvirus, also referred to as Human Herpesvirus 8 (HHV-8), which was first described in 1994 and is the subject of two articles, one by Luppi et al.1 and one by Pauk et al.,2 in this issue of the Journal. HHV-8 is closely related to the Epstein–Barr virus (Human Herpesvirus 4) and infects CD19+ B cells as well as the endothelial-derived spindle cells of Kaposi's sarcoma lesions.3 In addition . . .

  • Kaposi's Sarcoma-Associated Herpesvirus: Epidemiology, Virology, and Molecular Biology
    Advances in virus research, 1999
    Co-Authors: Ronit Sarid, Sonja J. Olsen, Patrick S. Moore
    Abstract:

    Publisher Summary Kaposi's sarcoma-associated Herpesvirus (KSHV) is the eighth Human Herpesvirus (HHVS) and is the subject of considerable interest because of its association with several major acquired immunodeficiency syndromes (AIDS)-related malignancies. Epidemiologic studies now largely agree that this virus is the required infectious cofactor responsible for Kaposi's sarcoma (KS) and related neoplastic disorders. Although the virus is important from a clinical and a public health standpoint, it also promises to provide a surprisingly rich source of basic information on how viruses induce cellular proliferation. As with other tumor viruses, there are also a number of important obstacles to the study of KSHV. Although KSHV can be cultured to high titer in naturally infected lymphoma cell lines, the virus cannot be sustainably cultivated from KS lesions analogous to Epstein-Barr virus (EBV or Human Herpesvirus 4/HHV4) in nasopharyngeal carcinoma.

Shrikant Kukreti - One of the best experts on this subject based on the ideXlab platform.

Paul M Lieberman - One of the best experts on this subject based on the ideXlab platform.

  • initiation of epstein barr virus lytic replication requires transcription and the formation of a stable rna dna hybrid molecule at orilyt
    Journal of Virology, 2011
    Co-Authors: Andrew J Rennekamp, Paul M Lieberman
    Abstract:

    Epstein-Barr virus (EBV) is a Human gammaHerpesvirus 1 (also known as Human Herpesvirus 4 [HHV4]) and the etiological agent responsible for infectious mononucleosis, oral hairy leukoplakia, AIDS immunoblastic lymphomas, posttransplant lymphoproliferative disease, 50% of Hodgkin's lymphomas, and the endemic forms of nasopharyngeal carcinoma and Burkitt's lymphoma (56, 79). Successful infection and viral spread, within and between individual hosts, are necessary prerequisites for EBV pathogenesis. Each of these requires productive lytic replication of the virus, which includes the duplication of its 170- to 175-kbp double-stranded DNA genome. To date, no antiviral drug has been approved, nor shown to be highly effective, in blocking EBV lytic replication, suggesting that mechanisms controlling viral DNA replication are sufficiently diverged from related members of the Herpesvirus family (2). Upon host cell infection and establishment of latency, Herpesvirus genomes, including EBV, adopt a closed circular conformation (11, 64). During lytic reactivation from viral latency, DNA replication must initiate from this circular template. The viral basic leucine zipper (b-ZIP) protein Zta (encoded by the immediate-early BZLF1 gene, and also known as Z, ZEBRA, and EB1) governs this process (10, 13, 17, 57, 69). Zta has been described as both a transcription factor and an origin binding protein, activating both virus early gene transcription and the EBV origin of lytic replication (OriLyt) (18, 24, 36, 38, 65). Zta's ability to activate OriLyt is thought to be at least partially due to its ability to bind viral replication proteins, perhaps recruiting them to the origin (19, 21, 34, 35, 82). The functional equivalent of Zta in herpes simplex virus 1 (HSV1) is the origin binding protein (OBP) encoded by the HSV1 UL9 gene. The HSV1 OBP is an ATP-dependent DNA helicase that appears to work together with the single-stranded DNA (ssDNA) binding protein ICP8 to accomplish DNA strand separation at the HSV1 origin OriS (25, 32). The EBV genome contains an ICP8 orthologue, referred to as BALF2, and a processive helicase (encoded by the BBLF4 gene) but lacks a replication initiator helicase like UL9. It remains unclear how a transcription factor like Zta, with no known enzymatic activity, mediates initiation of DNA replication and, specifically, DNA strand unwinding at OriLyt (53). EBV typically encodes two identical copies of OriLyt (although there are functional strains that contain only one copy), which include binding sites for Zta that are called Zta response elements (ZREs) (24, 38). Initial mapping studies by Hammerschmidt and Sugden identified two regions within OriLyt as necessary for replication (24). These regions, defined by testing overlapping EBV sequences in plasmid replication assays, mapped to nucleotides 52,632 to 52,944 (SstI-KpnI) and 53,207 to 53,581 (KpnI-NsiI) on the genome, respectively, and were later named the “upstream” and “downstream” essential elements (UEE and DEE). Finer mapping using deletions within the context of the larger 7.2-kbp BamHI-SalI fragment (nucleotides 48,848 to 56,084) narrowed the required regions to a 67-bp UEE (nucleotides 52,811 to 52,877) and an 87-bp DEE (nucleotides 53,342 to 53,428) (67). The UEE comprised the BHLF1/LF3 promoter (BHLF1p), including the TATA box, two ZREs (ZRE1 and -2), and a CCAAT box. All mutants tested that impaired BHLF1p function equally affected replication; however, not every mutation that impaired replication also impaired promoter function, suggesting that BHLF1p activity is required, though not sufficient, for replication. The DEE contains binding sites for the Sp1, Sp3, and ZBP-89 proteins, which interact with the core viral replication proteins (1, 23, 34, 65), including the EA-D processivity factor, which is able to activate the BHRF1 promoter via the downstream element (81, 82). The DEE also contains a homopurine-homopyrimidine sequence capable of forming a triple helix in vitro, and mutations that impair triple helix formation in vitro also disrupt DNA replication in vivo (48). These two essential core regions were thought to be flanked by nonessential auxiliary regions that influence the efficiency with which OriLyt-containing plasmids replicate in transient experiments (67). The approximately 2.5-kb BHLF1 RNA, transcribed off what was initially referred to as the NotI repeat, or ntr gene, in the BamHI H fragment of the EBV genome and whose promoter (BHLF1p) overlaps the UEE of the “left” copy of OriLyt (OriLytL), was first mapped by Jeang and Hayward (28). They were able to show that BHLF1 RNA was produced in response to 12-O-tetradecanoylphorbol-13-acetate (TPA) treatment in both B95-8 and Raji EBV-positive cell lines. The RNA start site was mapped to the +29 position, separated from the TATA box by a partially S1 nuclease-resistant 21-bp palindrome, and it spanned the NotI repeat (also known as internal repeat 2 [IR2]) region of the virus ending at an AATAAA poly(A) signal sequence (28, 30). The nucleotide sequence of the 5′ region of the RNA, up to the NotI repeats, was shown to be 82% GC rich. Additionally, an equally GC-rich transcript produced by the EBV LF3 gene, the positional equivalent of BHLF1 found in the second EBV lytic origin (OriLytR) with an identical promoter, was also identified (20). Interestingly, this gene, which encompasses the PstI repeat region of the EBV genome (also known as internal repeat 4 [IR4]), shares only limited sequence identity with BHLF1. The BHLF1/LF3 promoter (referred to as BHLF1p throughout this paper) is the strongest known Zta-responsive promoter (37), and BHLF1 and LF3 RNAs are the most abundant transcripts found during lytic replication (20, 30, 40). In fact, due to their prevalence, assays that detect these RNAs have been frequently used as tools for diagnosing EBV lytic infection in the clinic (6, 7, 62). In this work, we further investigated the mechanism of initiation of DNA replication at OriLytL. In an effort to define the minimal OriLyt, we found that one of the two divergent transcripts (BHLF1 or BHRF1) is essential for efficient DNA replication. We also found that the BHLF1 transcript provides a critical activity for OriLyt function in cis. The high guanine and cytosine (GC) content of the BHLF1 transcript, and its unknown function in lytic replication, prompted us to investigate its potential to form a stable RNA-DNA hybrid, or R-loop, structure similar to what has been observed at the mitochondrial DNA origin of replication (31, 76, 77) and at the immunoglobulin (Ig) locus during class switch recombination in B lymphocytes (22, 26). We used an antibody specific for RNA-DNA hybrid molecules to demonstrate the formation of such structures within the BHLF1 transcription unit. Furthermore, we show that Human RNase H1, an enzyme specific for RNA-DNA duplex hybrids, is a potent inhibitor of OriLyt replication and, specifically, recruitment of the ssDNA binding protein BALF2 to OriLyt, suggesting that the RNA-DNA hybrid may generate ssDNA important for lytic replication initiation.

Shikha Kaushik - One of the best experts on this subject based on the ideXlab platform.

Erle S. Robertson - One of the best experts on this subject based on the ideXlab platform.

  • Molecular biology of EBV in relationship to AIDS-associated oncogenesis.
    Cancer treatment and research, 2018
    Co-Authors: Bharat G. Bajaj, Masanao Murakami, Erle S. Robertson
    Abstract:

    Herpesvirus-induced disease is one of the most lethal factors which leads to high mortality in HIV/AIDS patients. EBV, also known as Human Herpesvirus 4, can transform naive B cells into immortalized cells in vitro through the regulation of cell cycle, cell proliferation, and apoptosis. EBV infection is associated with several lymphoma and epithelial cancers in Humans, which occurs at a much higher rate in immune deficient individuals than in healthy people, demonstrating that the immune system plays a vital role in inhibiting EBV activities. EBV latency infection proteins can mimic suppression cytokines or upregulate PD-1 on B cells to repress the cytotoxic T cells response. Many malignancies, including Hodgkin Lymphoma and non-Hodgkin's lymphomas occur at a much higher frequency in EBV positive individuals than in EBV negative people during the development of HIV infection. Importantly, understanding EBV pathogenesis at the molecular level will aid the development of novel therapies for EBV-induced diseases in HIV/AIDS patients.

  • GammaHerpesvirus Infection of Human Neuronal Cells
    mBio, 2015
    Co-Authors: Hem Chandra Jha, Devan Mehta, Darine W. El-naccache, Sanket Kumar Shukla, Colleen E. Kovacsics, Dennis L. Kolson, Erle S. Robertson
    Abstract:

    ABSTRACT GammaHerpesviruses Human Herpesvirus 4 (HHV4) and HHV8 are two prominent members of the Herpesvirus family associated with a number of Human cancers. HHV4, also known as Epstein-Barr virus (EBV), a ubiquitous gammaHerpesvirus prevalent in 90 to 95% of the Human population, is clinically associated with various neurological diseases such as primary central nervous system lymphoma, multiple sclerosis, Alzheimer9s disease, cerebellar ataxia, and encephalitis. However, the possibility that EBV and Kaposi9s sarcoma-associated Herpesvirus (KSHV) can directly infect neurons has been largely overlooked. This study has, for the first time, characterized EBV infection in neural cell backgrounds by using the Sh-Sy5y neuroblastoma cell line, teratocarcinoma Ntera2 neurons, and primary Human fetal neurons. Furthermore, we also demonstrated KSHV infection of neural Sh-Sy5y cells. These neuronal cells were infected with green fluorescent protein-expressing recombinant EBV or KSHV. Microscopy, genetic analysis, immunofluorescence, and Western blot analyses for specific viral antigens supported and validated the infection of these cells by EBV and KSHV and showed that the infection was efficient and productive. Progeny virus produced from infected neuronal cells efficiently infected fresh neuronal cells, as well as peripheral blood mononuclear cells. Furthermore, acyclovir was effective at inhibiting the production of virus from neuronal cells similar to lymphoblastoid cell lines; this suggests active lytic replication in infected neurons in vitro . These studies represent a potentially new in vitro model of EBV- and KSHV-associated neuronal disease development and pathogenesis. IMPORTANCE To date, no in vitro study has demonstrated gammaHerpesvirus infection of neuronal cells. Moreover, worldwide clinical findings have linked EBV to neuronal pathologies, including multiple sclerosis, primary central nervous system lymphoma, and Alzheimer9s disease. In this study, for the first time, we have successfully demonstrated the in vitro infection of Sh-Sy5y and Ntera2 cells, as well as Human primary neurons. We have also determined that the infection is predominately lytic. Additionally, we also report infection of neuronal cells by KSHV in vitro similar to that by EBV. These findings may open new avenues of consideration related to neuronal pathologies and infection with these viruses. Furthermore, their contribution to chronic infection linked to neuronal disease will provide new clues to potential new therapies.