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Journal of Virology, June 2009, p. 5869-5880, Vol. 83, No. 11
0022-538X/09/$08.00+0     doi:10.1128/JVI.01821-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

Kaposi's Sarcoma-Associated Herpesvirus K-bZIP Protein Is Necessary for Lytic Viral Gene Expression, DNA Replication, and Virion Production in Primary Effusion Lymphoma Cell Lines{triangledown} ,{dagger}

Sylvain Lefort and Louis Flamand*

Laboratory of Virology, Rheumatology and Immunology Research Center, CHUQ Research Center and Faculty of Medicine, Laval University, Quebec, Quebec, Canada

Received 29 August 2008/ Accepted 16 March 2009

Kaposi's sarcoma-associated herpesvirus (KSHV) is the causative agent of three human proliferative disorders, namely, Kaposi's sarcoma, primary effusion lymphomas (PEL), and multicentric Castleman's disease. Lytic DNA replication of KSHV, which is essential for viral propagation, requires the binding of at least two KSHV proteins, replication and transactivation activator (RTA) and K-bZIP, on the lytic origin of replication. Moreover, K-bZIP physically interacts with RTA and represses its transactivation activity on several viral promoters in transient transfection assays. To evaluate the physiological roles of K-bZIP in the context of PEL, we generated BCBL-1 cells with a tetracycline (Tet)-inducible small hairpin RNA (shRNA) directed against the K8 mRNA to knock down K-bZIP expression at different points during KSHV's life cycle. Using this model, we demonstrate that in the absence of K-bZIP expression, dramatic decreases in orf50, orf57, and orf26 transcript expression are observed. Similar effects were seen at the protein level for RTA (immediate-early protein) and K8.1 (late protein) expression. Interestingly, a direct correlation between K-bZIP levels and viral lytic mRNAs was noticed. As a consequence of K-bZIP knockdown, viral DNA replication and virion production were severely impaired. The same effects were observed following knockdown of K-bZIP in another PEL cell line, BC3. Finally, using shRNA-K8-inducible 293 cells, we report that de novo synthesis of K-bZIP is not necessary for initiation of infection and latency establishment. These data support the concept that K-bZIP is essential for lytic viral gene expression, viral DNA replication, and virus propagation in PEL cells.

* Corresponding author. Mailing address: Rheumatology and Immunology Research Center, Laval University, Room T1-49, 2705 Laurier Blvd., Quebec, Quebec, Canada G1V 4G2. Phone: (418) 656-4141, ext. 46164. Fax: (418) 654-2765. E-mail: Louis.Flamand{at}crchul.ulaval.ca

{triangledown} Published ahead of print on 25 March 2009.

{dagger} Supplemental material for this article may be found at http://jvi.asm.org/.

Journal of Virology, June 2009, p. 5869-5880, Vol. 83, No. 11
0022-538X/09/$08.00+0     doi:10.1128/JVI.01821-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Rossetto, C., Yamboliev, I., Pari, G. S. (2009). Kaposi's Sarcoma-Associated Herpesvirus/Human Herpesvirus 8 K-bZIP Modulates Latency-Associated Nuclear Protein-Mediated Suppression of Lytic Origin-Dependent DNA Synthesis. J. Virol. 83: 8492-8501 [Abstract] [Full Text]  


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