scholarly journals Lysine residues of interferon regulatory factor 7 affect the replication and transcription activator-mediated lytic replication of Kaposi's sarcoma-associated herpesvirus/human herpesvirus 8

2010 ◽  
Vol 92 (1) ◽  
pp. 181-187 ◽  
Author(s):  
T. Zhang ◽  
Y. Wang ◽  
L. Zhang ◽  
B. Liu ◽  
J. Xie ◽  
...  
Keyword(s):  
Kaposi's Sarcoma ◽  
Human Herpesvirus ◽  
Interferon Regulatory Factor ◽  
Lytic Replication ◽  
Human Herpesvirus 8 ◽  
Regulatory Factor ◽  
Transcription Activator ◽  
Herpesvirus 8 ◽  
Interferon Regulatory Factor 7 ◽  
Lysine Residues

scholarly journals Modulation of Human Herpesvirus 8/Kaposi's Sarcoma-Associated Herpesvirus Replication and Transcription Activator Transactivation by Interferon Regulatory Factor 7

2005 ◽  
Vol 79 (4) ◽  
pp. 2420-2431 ◽  
Author(s):  
Jinzhong Wang ◽  
Jun Zhang ◽  
Luwen Zhang ◽  
William Harrington ◽  
John T. West ◽  
...  
Keyword(s):  
Gene Expression ◽  
Kaposi's Sarcoma ◽  
Human Herpesvirus ◽  
Interferon Regulatory Factor ◽  
Human Herpesvirus 8 ◽  
Viral Gene ◽  
Regulatory Factor ◽  
Transcription Activator ◽  
Herpesvirus 8 ◽  
Interferon Regulatory Factor 7

ABSTRACT Human herpesvirus 8 (HHV-8)/Kaposi's sarcoma-associated herpesvirus infection goes through lytic and latent phases that are regulated by viral gene products, but very little is known about the involvement of host proteins. The replication and transcription activator (RTA) is a viral protein sufficient to initiate lytic replication by activating downstream genes, including the viral early gene open reading frame 57 (ORF 57), which codes for a posttranscriptional activator. In this study, we demonstrate that cellular interferon regulatory factor 7 (IRF-7) negatively regulates this process by competing with RTA for binding to the RTA response element in the ORF 57 promoter to down-regulate RTA-induced gene expression. We also show that alpha interferon represses RTA-mediated transactivation and that repression involves IRF-7. Our study indicates that upon HHV-8 infection, the host responds by suppression of lytic gene expression through binding of IRF-7 to the lytic viral gene promoter. These findings suggest that HHV-8 has developed a novel mechanism to induce but then subvert the innate antiviral response, specifically the interferon-signaling pathway, to regulate RTA activity and ultimately the viral latent/lytic replicative cycle.

scholarly journals Kaposi's Sarcoma-Associated Herpesvirus (Human Herpesvirus 8) Contains Hypoxia Response Elements: Relevance to Lytic Induction by Hypoxia

2003 ◽  
Vol 77 (12) ◽  
pp. 6761-6768 ◽  
Author(s):  
Muzammel Haque ◽  
David A. Davis ◽  
Victoria Wang ◽  
Isabelle Widmer ◽  
Robert Yarchoan
Keyword(s):  
Promoter Region ◽  
Kaposi's Sarcoma ◽  
Human Herpesvirus ◽  
Kaposi’S Sarcoma ◽  
Lytic Replication ◽  
Human Herpesvirus 8 ◽  
Viral Gene ◽  
Hypoxia Response ◽  
Herpesvirus 8 ◽  
Response Elements

ABSTRACT Kaposi's sarcoma (KS)-associated herpesvirus (KSHV), also known as human herpesvirus 8, is an etiologic agent of KS, primary effusion lymphoma (PEL), and multicentric Castleman's disease. We recently demonstrated that hypoxia can induce lytic replication of KSHV in PEL cell lines. Hypoxia induces the accumulation of hypoxia-inducible factors (HIF), and we hypothesized that the KSHV genome may respond to hypoxia through functional hypoxia response elements (HREs). Here, we demonstrate the presence of at least two promoters within the KSHV genome that are activated by hypoxia or hypoxia mimics. One is in the promoter region of the gene for Rta, the main lytic switch gene, and the other is within the promoter region of ORF34, a lytic gene of unknown function. The ORF34 promoter contains three putative consensus HREs oriented in the direction of the gene. Dissection and site-directed mutagenesis studies confirmed that one of the HREs of the ORF34 promoter is functional. Under conditions of hypoxia, the ORF34 promoter was strongly upregulated by HIF-1α and HIF-2α. By contrast, the promoter of the gene for Rta appeared to be preferentially upregulated by HIF-2α. Reverse transcription-PCR analysis revealed that specific messages for ORF34 and ORF50 are upregulated in BCBL-1 cells exposed to hypoxia. An HIF-1 binding and competition assay demonstrated that the HRE sequence from the ORF34 promoter can compete for HIF-1α binding to an erythropoietin HRE oligonucleotide while a mutant sequence cannot. Thus, we demonstrated that a viral gene can be activated by hypoxia through activation of a functional viral HRE. To our knowledge, this is the first example of a functional HRE in a viral promoter.

scholarly journals Human Herpesvirus 8 Infects and Replicates in Langerhans Cells and Interstitial Dermal Dendritic Cells and Impairs Their Function

2017 ◽  
Vol 91 (20) ◽  
Author(s):  
Giovanna Rappocciolo ◽  
Mariel Jais ◽  
Paolo A. Piazza ◽  
Diana C. DeLucia ◽  
Frank J. Jenkins ◽  
...  
Keyword(s):  
Dendritic Cells ◽  
Langerhans Cells ◽  
Kaposi's Sarcoma ◽  
Human Herpesvirus ◽  
Kaposi’S Sarcoma ◽  
Lytic Replication ◽  
Productive Infection ◽  
Receptor Protein ◽  
Human Herpesvirus 8 ◽  
Herpesvirus 8

ABSTRACT The predominant types of dendritic cells (DC) in the skin and mucosa are Langerhans cells (LC) and interstitial dermal DC (iDDC). LC and iDDC process cutaneous antigens and migrate out of the skin and mucosa to the draining lymph nodes to present antigens to T and B cells. Because of the strategic location of LC and iDDC and the ability of these cells to capture and process pathogens, we hypothesized that they could be infected with human herpesvirus 8 (HHV-8) (Kaposi's sarcoma [KS]-associated herpesvirus) and have an important role in the development of KS. We have previously shown that HHV-8 enters monocyte-derived dendritic cells (MDDC) through DC-SIGN, resulting in nonproductive infection. Here we show that LC and iDDC generated from pluripotent cord blood CD34+ cell precursors support productive infection with HHV-8. Anti-DC-SIGN monoclonal antibody (MAb) inhibited HHV-8 infection of iDDC, as shown by low expression levels of viral proteins and DNA. In contrast, blocking of both langerin and the receptor protein tyrosine kinase ephrin A2 was required to inhibit HHV-8 infection of LC. Infection with HHV-8 did not alter the cell surface expression of langerin on LC but downregulated the expression of DC-SIGN on iDDC, as we previously reported for MDDC. HHV-8-infected LC and iDDC had a reduced ability to stimulate allogeneic CD4+ T cells in the mixed-lymphocyte reaction. These results indicate that HHV-8 can target both LC and iDDC for productive infection via different receptors and alter their function, supporting their potential role in HHV-8 pathogenesis and KS. IMPORTANCE Here we show that HHV-8, a DNA tumor virus that causes Kaposi's sarcoma, infects three types of dendritic cells: monocyte-derived dendritic cells, Langerhans cells, and interstitial dermal dendritic cells. We show that different receptors are used by this virus to infect these cells. DC-SIGN is a major receptor for infection of both monocyte-derived dendritic cells and interstitial dermal dendritic cells, yet the virus fully replicates only in the latter. HHV-8 uses langerin and the ephrin A2 receptor to infect Langerhans cells, which support full HHV-8 lytic replication. This infection of Langerhans cells and interstitial dermal dendritic cells results in an impaired ability to stimulate CD4+ helper T cell responses. Taken together, our data show that HHV-8 utilizes alternate receptors to differentially infect and replicate in these tissue-resident DC and support the hypothesis that these cells play an important role in HHV-8 infection and pathogenesis.

scholarly journals Kaposi's Sarcoma-Associated Herpesvirus (Human Herpesvirus 8) Infection of Human Fibroblast Cells Occurs through Endocytosis

2003 ◽  
Vol 77 (14) ◽  
pp. 7978-7990 ◽  
Author(s):  
Shaw M. Akula ◽  
Pramod P. Naranatt ◽  
Neelam-Sharma Walia ◽  
Fu-Zhang Wang ◽  
Barbara Fegley ◽  
...  
Keyword(s):  
Kaposi's Sarcoma ◽  
Human Herpesvirus ◽  
Kaposi’S Sarcoma ◽  
Lytic Replication ◽  
Human Herpesvirus 8 ◽  
Target Cells ◽  
Fibroblast Cells ◽  
Coated Pits ◽  
Herpesvirus 8 ◽  
Endocytic Vesicles

ABSTRACT Kaposi's sarcoma (KS)-associated herpesvirus or human herpesvirus 8 (HHV-8) DNA and transcripts have been detected in the B cells, macrophages, keratinocytes, and endothelial and epithelial cells of KS patients. In vitro, HHV-8 infects human B, endothelial, epithelial, and fibroblast cells, as well as animal cells, and the infection is characterized by (i) absence of lytic replication by the input virus and (ii) latent infection. For its initial binding to target cells, HHV-8 uses ubiquitous heparan sulfate molecules via its envelope-associated glycoproteins gB and gpK8.1A. HHV-8 also interacts with the α3β1 integrin via its glycoprotein gB, and virus binding studies suggest that α3β1 is one of the HHV-8 entry receptors (S. M. Akula, N. P. Pramod, F. Z. Wang, and B. Chandran, Cell 108:407-419, 2002). In this study, morphological and biochemical techniques were used to examine the entry of HHV-8 into human foreskin fibroblasts (HFF). HHV-8 was detected in coated vesicles and in large, smooth-surfaced endocytic vesicles. Fusion of viral envelope with the vesicle wall was also observed. In immune electron microscopy, anti-HHV-8 gB antibodies colocalized with virus-containing endocytic vesicles. In fluorescence microscopic analyses, transferrin was colocalized with HHV-8. HHV-8 infection was significantly inhibited by preincubation of cells with chlorpromazine HCl, which blocks endocytosis via clathrin-coated pits, but not by nystatin and cholera toxin B, which blocks endocytosis via caveolae and induces the dissociation of lipid rafts, respectively. Infection was also inhibited by blocking the acidification of endosomes by NH4Cl and bafilomycin A. Inhibition of HHV-8 open reading frame 73 gene expression by chlorpromazine HCl, bafilomycin A, and NH4Cl demonstrated that the virions in the vesicles could proceed to cause an infection. Taken together, these findings suggest that for its infectious entry into HFF, HHV-8 uses clathrin-mediated endocytosis and a low-pH intracellular environment.

scholarly journals Comparative Study of Regulation of RTA-Responsive Genes in Kaposi's Sarcoma-Associated Herpesvirus/Human Herpesvirus 8

2003 ◽  
Vol 77 (17) ◽  
pp. 9451-9462 ◽  
Author(s):  
Moon Jung Song ◽  
Hongyu Deng ◽  
Ren Sun
Keyword(s):  
Gene Expression ◽  
Life Cycle ◽  
Transcription Initiation ◽  
Target Genes ◽  
Human Herpesvirus ◽  
Lytic Replication ◽  
Human Herpesvirus 8 ◽  
Transcription Activator ◽  
Herpesvirus 8 ◽  
Direct Binding

ABSTRACT Replication and transcription activator (RTA) (also referred to as ORF50), an immediate-early gene product of Kaposi's sarcoma-associated herpesvirus (KSHV)/(human herpesvirus 8), plays a critical role in balancing the viral life cycle between latency and lytic replication. RTA has been shown to act as a strong transcription activator for several downstream genes of KSHV. Direct binding of RTA to DNA is thought to be one of the important mechanisms for transactivation of target genes, while indirect mechanisms are also implicated in RTA transactivation of certain selected genes. This study demonstrated direct binding of the DNA-binding domain of RTA (Rdbd) to a Kaposin (Kpsn) promoter sequence, which is highly homologous to the RTA-responsive element (RRE) of the PAN promoter. We undertook a comparative study of the RREs of PAN RNA, ORF57, vIL-6, and Kpsn to understand how RTA regulates gene expression during lytic replication. Comparing RNA abundance and transcription initiation rates of these RTA target genes in virus-infected cells suggested that the transcription initiation rate of the promoters is a major determinant of viral gene expression, rather than stability of the transcripts. RTA-mediated transactivation of reporters containing each RRE showed that their promoter strengths in a transient-transfection system were comparable to their transcription rates during reactivation. Moreover, our electrophoretic mobility shift assays of each RRE demonstrated that the highly purified Rdbd protein directly bound to the RREs. Based on these results, we conclude that direct binding of RTA to these target sequences contributes to their gene expression to various extents during the lytic life cycle of KSHV.

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