scholarly journals Kaposi's Sarcoma-Associated Herpesvirus Latency-Associated Nuclear Antigen Interacts with Bromodomain Protein Brd4 on Host Mitotic Chromosomes

2006 ◽  
Vol 80 (18) ◽  
pp. 8909-8919 ◽  
Author(s):  
Jianxin You ◽  
Viswanathan Srinivasan ◽  
Gerald V. Denis ◽  
William J. Harrington ◽  
Mary E. Ballestas ◽  
...  
Keyword(s):  
Kaposi's Sarcoma ◽  
Kaposi’S Sarcoma ◽  
Host Cells ◽  
Nuclear Antigen ◽  
Mitotic Chromosomes ◽  
Kaposi's Sarcoma Associated Herpesvirus ◽  
Kaposi’S Sarcoma Associated Herpesvirus ◽  
Chromosome Binding

ABSTRACT The latency-associated nuclear antigen (LANA) of Kaposi's sarcoma-associated herpesvirus (KSHV) is required for viral episome maintenance in host cells during latent infection. Two regions of the protein have been implicated in tethering LANA/viral episomes to the host mitotic chromosomes, and LANA chromosome-binding sites are subjects of high interest. Because previous studies had identified bromodomain protein Brd4 as the mitotic chromosome anchor for the bovine papillomavirus E2 protein, which tethers the viral episomes to host mitotic chromosomes (J. You, J. L. Croyle, A. Nishimura, K. Ozato, and P. M. Howley, Cell 117:349-360, 2004, and J. You, M. R. Schweiger, and P. M. Howley, J. Virol. 79:14956-14961, 2005), we examined whether KSHV LANA interacts with Brd4. We found that LANA binds Brd4 in vivo and in vitro and that the binding is mediated by a direct protein-protein interaction between the ET (extraterminal) domain of Brd4 and a carboxyl-terminal region of LANA previously implicated in chromosome binding. Brd4 associates with mitotic chromosomes throughout mitosis and demonstrates a strong colocalization with LANA and the KSHV episomes on host mitotic chromosomes. Although another bromodomain protein, RING3/Brd2, binds to LANA in a similar fashion in vitro, it is largely excluded from the mitotic chromosomes in KSHV-uninfected cells and is partially recruited to the chromosomes in KSHV-infected cells. These data identify Brd4 as an interacting protein for the carboxyl terminus of LANA on mitotic chromosomes and suggest distinct functional roles for the two bromodomain proteins RING3/Brd2 and Brd4 in LANA binding. Additionally, because Brd4 has recently been shown to have a role in transcription, we examined whether Brd4 can regulate the CDK2 promoter, which can be transactivated by LANA.

scholarly journals ORF73 of Herpesvirus Saimiri, a Viral Homolog of Kaposi's Sarcoma-Associated Herpesvirus, Modulates the Two Cellular Tumor Suppressor Proteins p53 and pRb

2004 ◽  
Vol 78 (19) ◽  
pp. 10336-10347 ◽  
Author(s):  
Sumit Borah ◽  
Subhash C. Verma ◽  
Erle S. Robertson
Keyword(s):  
Cell Cycle ◽  
Kaposi's Sarcoma ◽  
Kaposi’S Sarcoma ◽  
Herpesvirus Saimiri ◽  
Nuclear Antigen ◽  
Kaposi's Sarcoma Associated Herpesvirus ◽  
Kaposi’S Sarcoma Associated Herpesvirus ◽  
P53 Inactivation

ABSTRACT All known DNA tumor viruses are known to target and inactivate two main cell cycle regulatory proteins, retinoblastoma protein (pRb) and p53. Inactivation of pRb promotes host cell cycle progression into S phase, and inactivation of p53 promotes cell immortalization. The DNA tumor virus Kaposi's sarcoma associated herpesvirus (KSHV)-encoded latency-associated nuclear antigen (LANA) was shown to target and inactivate pRb as well as p53. In this report we provide evidence that these functions are conserved in the homologous protein encoded by the related gammaherpesvirus herpesvirus saimiri (HVS). ORF73, the HVS homologue of LANA, is shown to bind both p53 and pRb in vitro and in vivo, to colocalize with p53 in human T cells infected with HVS, and in cells overexpressing both ORF73 and p53, as well as to adversely influence pRB/E2F and p53 transcriptional regulation. The C terminus of LANA, the region most highly conserved in ORF73, is shown to be responsible for both pRb and p53 interactions, supporting the hypothesis that these functions are conserved in both homologues. Finally, the region of p53 targeted by LANA (and ORF73) maps to the domain required for tetramerization. However, preliminary cross-linking studies do not detect disruption of p53 tetramerization by either LANA or HVS-encoded ORF73, suggesting that p53 inactivation may be by a mechanism independent of tetramer disruption.

scholarly journals Role of Kaposi's Sarcoma-Associated Herpesvirus C-Terminal LANA Chromosome Binding in Episome Persistence

2009 ◽  
Vol 83 (9) ◽  
pp. 4326-4337 ◽  
Author(s):  
Brenna Kelley-Clarke ◽  
Erika De Leon-Vazquez ◽  
Katherine Slain ◽  
Andrew J. Barbera ◽  
Kenneth M. Kaye
Keyword(s):  
Kaposi's Sarcoma ◽  
Kaposi’S Sarcoma ◽  
Chromosome Association ◽  
Mitotic Chromosomes ◽  
Dividing Cells ◽  
Kaposi's Sarcoma Associated Herpesvirus ◽  
Self Association ◽  
Kaposi’S Sarcoma Associated Herpesvirus ◽  
Chromosome Binding

ABSTRACT Kaposi's sarcoma-associated herpesvirus (KSHV) LANA is an 1,162-amino-acid protein that tethers terminal repeat (TR) DNA to mitotic chromosomes to mediate episome persistence in dividing cells. C-terminal LANA self-associates to bind TR DNA. LANA contains independent N- and C-terminal chromosome binding regions. N-terminal LANA binds histones H2A/H2B to attach to chromosomes, and this binding is essential for episome persistence. We now investigate the role of C-terminal chromosome binding in LANA function. Alanine substitutions for LANA residues 1068LKK1070 and 1125SHP1127 severely impaired chromosome binding but did not reduce the other C-terminal LANA functions of self-association or DNA binding. The 1068LKK1070 and 1125SHP1127 substitutions did not reduce LANA's inhibition of RB1-induced growth arrest, transactivation of the CDK2 promoter, or C-terminal LANA's inhibition of p53 activation of the BAX promoter. When N-terminal LANA was wild type, the 1068LKK1070 and 1125SHP1127 substitutions also did not reduce LANA chromosome association or episome persistence. However, when N-terminal LANA binding to chromosomes was modestly diminished, the substitutions in 1068LKK1070 and 1125SHP1127 dramatically reduced both LANA chromosome association and episome persistence. These data suggest a model in which N- and C-terminal LANA cooperatively associates with chromosomes to mediate full-length LANA chromosome binding and viral persistence.

scholarly journals Early Events in Kaposi's Sarcoma-Associated Herpesvirus Infection of Target Cells

2009 ◽  
Vol 84 (5) ◽  
pp. 2188-2199 ◽  
Author(s):  
Bala Chandran
Keyword(s):  
Kaposi's Sarcoma ◽  
Kaposi’S Sarcoma ◽  
Target Cells ◽  
Mode Of Entry ◽  
Successful Infection ◽  
Kaposi's Sarcoma Associated Herpesvirus ◽  
Kaposi’S Sarcoma Associated Herpesvirus ◽  
Cell Signaling Pathways

ABSTRACT Kaposi's sarcoma-associated herpesvirus (KSHV), the most recently identified member of the herpesvirus family, infects a variety of target cells in vitro and in vivo. This minireview surveys current information on the early events of KSHV infection, including virus-receptor interactions, involved envelope glycoproteins, mode of entry, intracellular trafficking, and initial viral and host gene expression programs. We describe data supporting the hypothesis that KSHV manipulates preexisting host cell signaling pathways to allow successful infection. The various signaling events triggered by infection, and their potential roles in the different stages of infection and disease pathogenesis, are summarized.

scholarly journals CAK-independent Activation of CDK6 by a Viral Cyclin

2001 ◽  
Vol 12 (12) ◽  
pp. 3987-3999 ◽  
Author(s):  
Philipp Kaldis ◽  
Päivi M. Ojala ◽  
Lily Tong ◽  
Tomi P. Mäkelä ◽  
Mark J. Solomon
Keyword(s):  
Conformational Changes ◽  
Kaposi's Sarcoma ◽  
Cell Cycle Progression ◽  
Kaposi’S Sarcoma ◽  
Binding Assays ◽  
Kaposi's Sarcoma Associated Herpesvirus ◽  
Induced Apoptosis ◽  
Kaposi’S Sarcoma Associated Herpesvirus

In normal cells, activation of cyclin-dependent kinases (cdks) requires binding to a cyclin and phosphorylation by the cdk-activating kinase (CAK). The Kaposi's sarcoma-associated herpesvirus encodes a protein with similarity to D-type cyclins. This KSHV-cyclin activates CDK6, alters its substrate specificity, and renders CDK6 insensitive to inhibition by the cdk inhibitor p16INK4a. Here we investigate the regulation of the CDK6/KSHV-cyclin kinase with the use of purified proteins and a cell-based assay. We find that KSHV-cyclin can activate CDK6 independent of phosphorylation by CAK in vitro. In addition, CAK phosphorylation decreased the p16INK4asensitivity of CDK6/KSHV-cyclin complexes. In cells, expression of CDK6 or to a lesser degree of a nonphosphorylatable CDK6T177Atogether with KSHV-cyclin induced apoptosis, indicating that CDK6 activation by KSHV-cyclin can proceed in the absence of phosphorylation by CAK in vivo. Coexpression of p16 partially protected cells from cell death. p16 and KSHV-cyclin can form a ternary complex with CDK6 that can be detected by binding assays as well as by conformational changes in CDK6. The Kaposi's sarcoma-associated herpesvirus has adopted a clever strategy to render cell cycle progression independent of mitogenic signals, cdk inhibition, or phosphorylation by CAK.

scholarly journals Kaposi's Sarcoma-Associated Herpesvirus LANA2 Is a B-Cell-Specific Latent Viral Protein That Inhibits p53

2001 ◽  
Vol 75 (1) ◽  
pp. 429-438 ◽  
Author(s):  
Carmen Rivas ◽  
Ai-En Thlick ◽  
Carlo Parravicini ◽  
Patrick S. Moore ◽  
Yuan Chang
Keyword(s):  
Kaposi's Sarcoma ◽  
Primary Effusion Lymphoma ◽  
Blot Hybridization ◽  
Human Herpesvirus ◽  
Kaposi’S Sarcoma ◽  
Nuclear Antigen ◽  
P53 Overexpression ◽  
Kaposi's Sarcoma Associated Herpesvirus ◽  
Kaposi’S Sarcoma Associated Herpesvirus

ABSTRACT Kaposi's sarcoma-associated herpesvirus (KSHV), or human herpesvirus 8, is associated with three proliferative diseases ranging from viral cytokine-induced hyperplasia to monoclonal neoplasia: multicentric Castleman's disease (CD), Kaposi's sarcoma (KS), and primary effusion lymphoma (PEL). Here we report a new latency-associated 1,704-bp KSHV spliced gene belonging to a cluster of KSHV sequences having homology to the interferon regulatory factor (IRF) family of transcription factors. ORFK10.5 encodes a protein, latency-associated nuclear antigen 2 (LANA2), which is expressed in KSHV-infected hematopoietic tissues, including PEL and CD but not KS lesions. LANA2 is abundantly expressed in the nuclei of cultured KSHV-infected B cells. Transcription of K10.5 in PEL cell cultures is not inhibited by DNA polymerase inhibitors nor significantly induced by phorbol ester treatment. Unlike LANA1, LANA2 does not elicit a serologic response from patients with KS, PEL, or CD as measured by Western blot hybridization. Both KSHV vIRF1 (ORFK9) and LANA2 (ORFK10.5) appear to have arisen through gene duplication of a captured cellular IRF gene. LANA2 is a potent inhibitor of p53-induced transcription in reporter assays. LANA2 antagonizes apoptosis due to p53 overexpression in p53-null SAOS-2 cells and apoptosis due to doxorubicin treatment of wild-type p53 U2OS cells. While LANA2 specifically interacts with amino acids 290 to 393 of p53 in glutathione S-transferase pull-down assays, we were unable to demonstrate LANA2-p53 interaction in vivo by immunoprecipitation. These findings show that KSHV has tissue-specific latent gene expression programs and identify a new latent protein which may contribute to KSHV tumorigenesis in hematopoietic tissues via p53 inhibition.

scholarly journals Chromosome Binding Site of Latency-Associated Nuclear Antigen of Kaposi's Sarcoma-Associated Herpesvirus Is Essential for Persistent Episome Maintenance and Is Functionally Replaced by Histone H1

2002 ◽  
Vol 76 (24) ◽  
pp. 12917-12924 ◽  
Author(s):  
Hirohiko Shinohara ◽  
Masaya Fukushi ◽  
Masaya Higuchi ◽  
Masayasu Oie ◽  
Osamu Hoshi ◽  
...  
Keyword(s):  
Cell Line ◽  
Kaposi's Sarcoma ◽  
Kaposi’S Sarcoma ◽  
Histone H1 ◽  
Nuclear Antigen ◽  
Mitotic Chromosomes ◽  
Dividing Cells ◽  
Kaposi’S Sarcoma Associated Herpesvirus ◽  
Chromosome Binding

ABSTRACT Latency-associated nuclear antigen 1 (LANA1) of Kaposi's sarcoma-associated herpesvirus (KSHV; human herpesvirus 8) persistently maintains a plasmid containing the KSHV latent origin of replication (oriP) as a closed circular episome in dividing cells. In this study, we investigated the involvement of chromosome binding activity of LANA1 in persistent episome maintenance. Deletion of the N-terminal 22 amino acids of LANA1 (ΔN-LANA) inhibited the interaction with mitotic chromosomes in a human cell line, and the mutant concomitantly lost activity for the long-term episome maintenance of a plasmid containing viral oriP in a human B-cell line. However, a chimera of ΔN-LANA with histone H1, a cellular chromosome component protein, rescued the association with mitotic chromosomes as well as the long-term episome maintenance of the oriP-containing plasmid. Our results suggest that tethering of KSHV episomes to mitotic chromosomes by LANA1 is crucial in mediating the long-term maintenance of viral episomes in dividing cells.

scholarly journals Expression in a Recombinant Murid Herpesvirus 4 Reveals the In Vivo Transforming Potential of the K1 Open Reading Frame of Kaposi's Sarcoma-Associated Herpesvirus

2004 ◽  
Vol 78 (16) ◽  
pp. 8878-8884 ◽  
Author(s):  
Jill Douglas ◽  
Bernadette Dutia ◽  
Susan Rhind ◽  
James P. Stewart ◽  
Simon J. Talbot
Keyword(s):  
Kaposi's Sarcoma ◽  
Fluorescent Protein ◽  
Salivary Gland Tumor ◽  
Kaposi’S Sarcoma ◽  
Common Marmoset ◽  
Kaposi's Sarcoma Associated Herpesvirus ◽  
Herpesvirus 4 ◽  
Kaposi’S Sarcoma Associated Herpesvirus

ABSTRACT Murid herpesvirus 4 (commonly called MHV-68) is closely related to Kaposi's sarcoma-associated herpesvirus (KSHV) and provides an excellent model system for investigating gammaherpesvirus-associated pathogenesis. MHV-76 is a naturally occurring deletion mutant of MHV-68 that lacks 9,538 bp of the left end of the unique portion of the genome encoding nonessential pathogenesis-related genes. The KSHV K1 protein has been shown to transform rodent fibroblasts in vitro and common marmoset T lymphocytes in vivo. Using homologous recombination techniques, we successfully generated recombinants of MHV-76 that encode green fluorescent protein (MHV76-GFP) and KSHV K1 (MHV76-K1). The replication of MHV76-GFP and MHV76-K1 in cell culture was identical to that of MHV-76. However, infection of BALB/c mice via the intranasal route revealed that MHV76-K1 replicated to a 10-fold higher titer than MHV76-GFP in the lungs at day 5 postinfection (p.i.). We observed type 2 pneumocyte proliferation in areas of consolidation and interstitial inflammation of mice infected with MHV76-K1 at day 10 p.i. MHV76-K1 established a 2- to 3-fold higher latent viral load than MHV76-GFP in the spleens of infected mice on days 10 and 14 p.i., although this was 10-fold lower than that established by wild-type MHV-76. A salivary gland tumor was present in one of four mice infected with MHV76-K1, as well as an increased inflammatory response in the lungs at day 120 p.i. compared with that of mice infected with MHV-76 and MHV76-GFP.

scholarly journals The Kaposi's Sarcoma-Associated Herpesvirus Latency-Associated Nuclear Antigen 1 N Terminus Is Essential for Chromosome Association, DNA Replication, and Episome Persistence

2004 ◽  
Vol 78 (1) ◽  
pp. 294-301 ◽  
Author(s):  
Andrew J. Barbera ◽  
Mary E. Ballestas ◽  
Kenneth M. Kaye
Keyword(s):  
Dna Replication ◽  
Kaposi's Sarcoma ◽  
Kaposi’S Sarcoma ◽  
Chromosome Association ◽  
Nuclear Antigen ◽  
Mitotic Chromosomes ◽  
Proliferating Cells ◽  
N Terminus ◽  
Kaposi's Sarcoma Associated Herpesvirus ◽  
Kaposi’S Sarcoma Associated Herpesvirus

ABSTRACT To persist in latently infected, proliferating cells, Kaposi's sarcoma-associated herpesvirus (KSHV) episomes must replicate and efficiently segregate to progeny nuclei. Episome persistence in uninfected cells requires latency-associated nuclear antigen 1 (LANA1) in trans and cis-acting KSHV terminal repeat (TR) DNA. The LANA1 C terminus binds TR DNA, and LANA1 mediates TR-associated DNA replication in transient assays. LANA1 also concentrates at sites of KSHV TR DNA episomes along mitotic chromosomes, consistent with a tethering role to efficiently segregate episomes to progeny nuclei. LANA1 amino acids 5 to 22 constitute a chromosome association region (Piolot et al., J. Virol. 75:3948-3959, 2001). We now investigate LANA1 residues 5 to 22 with scanning alanine substitutions. Mutations targeting LANA1 5GMR7, 8LRS10, and 11GRS13 eliminated chromosome association, DNA replication, and episome persistence. LANA1 mutated at 14TG15 retained the ability to associate with chromosomes but was partially deficient in DNA replication and episome persistence. These results provide genetic support for a key role of the LANA1 N terminus in chromosome association, LANA1-mediated DNA replication, and episome persistence.

scholarly journals Exploring the DNA Binding Interactions of the Kaposi's Sarcoma-Associated Herpesvirus Lytic Switch Protein by Selective Amplification of Bound Sequences In Vitro

2006 ◽  
Vol 80 (6) ◽  
pp. 2958-2967 ◽  
Author(s):  
Joseph Ziegelbauer ◽  
Adam Grundhoff ◽  
Don Ganem
Keyword(s):  
Protein Interactions ◽  
Kaposi's Sarcoma ◽  
Genomic Library ◽  
Consensus Sequence ◽  
Kaposi’S Sarcoma ◽  
Genomic Libraries ◽  
Kaposi's Sarcoma Associated Herpesvirus ◽  
Kaposi’S Sarcoma Associated Herpesvirus

ABSTRACT The lytic switch protein RTA of Kaposi's sarcoma-associated herpesvirus (KSHV) can be targeted to DNA by either direct sequence-specific recognition or via protein-protein interactions with host transcription factors. We have searched for sequences capable of direct RTA binding by screening synthetic oligonucleotide pools and KSHV genomic libraries for RTA-interacting elements, using repeated cycles of in vitro binding followed by amplification of the bound sequences. Multiple low-affinity sequences were recovered from the random pools, with generation of only a weak consensus sequence. The genomic library, by contrast, yielded many biologically relevant fragments, most of which could be shown to interact with RTA in vitro and some of which likely play important regulatory roles in vivo. Surprisingly, the most highly selected fragment came from the promoter of a late gene (gB) and contained at least two direct RTA binding sites, as well as one RBP-Jκ binding site. This raises the possibility that some late KSHV genes may also be subject to direct RTA regulation, though indirect models are not excluded.

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