Kaposi's sarcoma-associated herpesvirus (KSHV) infection goes through latent and lytic phases, which are controlled by the viral replication and transcription activator (RTA). Upon KSHV infection, the host responds by suppressing RTA-activated lytic gene expression through interferon regulatory factor 7 (IRF-7), a key regulator of host innate immune response. Lysine residues are potential sites for post-translational modification of IRF-7, and were suggested to be critical for its activity. In this study, we analysed the 15 lysine residues for their effects on IRF-7 function by site-directed mutagenesis. We found that some mutations affect the ability of IRF-7 to activate interferon (IFN)-1 and IFN- promoters, to suppress RTA-mediated lytic gene expression and to repress KSHV reactivation and lytic replication. However, other mutations affect only a subset of these four functions. These findings demonstrate that the lysine residues of IRF-7 play important roles in mediating IFN synthesis and modulating viral lytic replication.


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  1. Bu, W., Palmeri, D., Krishnan, R., Marin, R., Aris, V. M., Soteropoulos, P. & Lukac, D. M.(2008). Identification of direct transcriptional targets of the Kaposi's sarcoma-associated herpesvirus Rta lytic switch protein by conditional nuclear localization. J Virol 82, 10709–10723.[CrossRef] [Google Scholar]
  2. Caillaud, A., Prakash, A., Smith, E., Masumi, A., Hovanessian, A. G., Levy, D. E. & Marie, I.(2002). Acetylation of interferon regulatory factor-7 by p300/CREB-binding protein (CBP)-associated factor (PCAF) impairs its DNA binding. J Biol Chem 277, 49417–49421.[CrossRef] [Google Scholar]
  3. Caillaud, A., Hovanessian, A. G., Levy, D. E. & Marie, I. J.(2005). Regulatory serine residues mediate phosphorylation-dependent and phosphorylation-independent activation of interferon regulatory factor 7. J Biol Chem 280, 17671–17677.[CrossRef] [Google Scholar]
  4. Chang, Y., Cesarman, E., Pessin, M. S., Lee, F., Culpepper, J., Knowles, D. M. & Moore, P. S.(1994). Identification of herpesvirus-like DNA sequences in AIDS-associated Kaposi's sarcoma. Science 266, 1865–1869.[CrossRef] [Google Scholar]
  5. Chang, T. H., Kubota, T., Matsuoka, M., Jones, S., Bradfute, S. B., Bray, M. & Ozato, K.(2009). Ebola Zaire virus blocks type I interferon production by exploiting the host SUMO modification machinery. PLoS Pathog 5, e1000493.[CrossRef] [Google Scholar]
  6. Chen, J., Ye, F., Xie, J., Kuhne, K. & Gao, S. J.(2009). Genome-wide identification of binding sites for Kaposi's sarcoma-associated herpesvirus lytic switch protein, RTA. Virology 386, 290–302.[CrossRef] [Google Scholar]
  7. Deng, H., Young, A. & Sun, R.(2000). Auto-activation of the rta gene of human herpesvirus-8/Kaposi's sarcoma-associated herpesvirus. J Gen Virol 81, 3043–3048. [Google Scholar]
  8. Duan, W., Wang, S., Liu, S. & Wood, C.(2001). Characterization of Kaposi's sarcoma-associated herpesvirus/human herpesvirus-8 ORF57 promoter. Arch Virol 146, 403–413.[CrossRef] [Google Scholar]
  9. Gradoville, L., Gerlach, J., Grogan, E., Shedd, D., Nikiforow, S., Metroka, C. & Miller, G.(2000). Kaposi's sarcoma-associated herpesvirus open reading frame 50/Rta protein activates the entire viral lytic cycle in the HH-B2 primary effusion lymphoma cell line. J Virol 74, 6207–6212.[CrossRef] [Google Scholar]
  10. Grundhoff, A. & Ganem, D.(2004). Inefficient establishment of KSHV latency suggests an additional role for continued lytic replication in Kaposi sarcoma pathogenesis. J Clin Invest 113, 124–136.[CrossRef] [Google Scholar]
  11. Honda, K., Yanai, H., Negishi, H., Asagiri, M., Sato, M., Mizutani, T., Shimada, N., Ohba, Y., Takaoka, A. & other authors(2005). IRF-7 is the master regulator of type-I interferon-dependent immune responses. Nature 434, 772–777.[CrossRef] [Google Scholar]
  12. Katano, H., Sato, Y., Itoh, H. & Sata, T.(2001). Expression of human herpesvirus 8 (HHV-8)-encoded immediate early protein, open reading frame 50, in HHV-8-associated diseases. J Hum Virol 4, 96–102. [Google Scholar]
  13. Kawai, T., Sato, S., Ishii, K. J., Coban, C., Hemmi, H., Yamamoto, M., Terai, K., Matsuda, M., Inoue, J. & other authors(2004). Interferon-α induction through Toll-like receptors involves a direct interaction of IRF7 with MyD88 and TRAF6. Nat Immunol 5, 1061–1068.[CrossRef] [Google Scholar]
  14. Kubota, T., Matsuoka, M., Chang, T. H., Tailor, P., Sasaki, T., Tashiro, M., Kato, A. & Ozato, K.(2008). Virus infection triggers SUMOylation of IRF3 and IRF7, leading to the negative regulation of type I interferon gene expression. J Biol Chem 283, 25660–25670.[CrossRef] [Google Scholar]
  15. Lukac, D. M., Renne, R., Kirshner, J. R. & Ganem, D.(1998). Reactivation of Kaposi's sarcoma-associated herpesvirus infection from latency by expression of the ORF 50 transactivator, a homolog of the EBV R protein. Virology 252, 304–312.[CrossRef] [Google Scholar]
  16. Marie, I., Smith, E., Prakash, A. & Levy, D. E.(2000). Phosphorylation-induced dimerization of interferon regulatory factor 7 unmasks DNA binding and a bipartite transactivation domain. Mol Cell Biol 20, 8803–8814.[CrossRef] [Google Scholar]
  17. Moore, P. S. & Chang, Y.(2003). Kaposi's sarcoma-associated herpesvirus immunoevasion and tumorigenesis: two sides of the same coin? Annu Rev Microbiol 57, 609–639.[CrossRef] [Google Scholar]
  18. Naranatt, P. P., Krishnan, H. H., Svojanovsky, S. R., Bloomer, C., Mathur, S. & Chandran, B.(2004). Host gene induction and transcriptional reprogramming in Kaposi's sarcoma-associated herpesvirus (KSHV/HHV-8)-infected endothelial, fibroblast, and B cells: insights into modulation events early during infection. Cancer Res 64, 72–84.[CrossRef] [Google Scholar]
  19. Ning, S., Campos, A. D., Darnay, B. G., Bentz, G. L. & Pagano, J. S.(2008). TRAF6 and the three C-terminal lysine sites on IRF7 are required for its ubiquitination-mediated activation by the tumor necrosis factor receptor family member latent membrane protein 1. Mol Cell Biol 28, 6536–6546.[CrossRef] [Google Scholar]
  20. Panne, D., Maniatis, T. & Harrison, S. C.(2007). An atomic model of the interferon-β enhanceosome. Cell 129, 1111–1123.[CrossRef] [Google Scholar]
  21. Qin, Y., Liu, Z., Zhang, T., Wang, Y., Li, X. & Wang, J.(2010). Generation and application of polyclonal antibody against replication and transcription activator of Kaposi's sarcoma-associated herpesvirus. Appl Biochem Biotechnol 160, 1217–1226.[CrossRef] [Google Scholar]
  22. Song, M. J., Brown, H. J., Wu, T. T. & Sun, R.(2001). Transcription activation of polyadenylated nuclear RNA by Rta in human herpesvirus 8/Kaposi's sarcoma-associated herpesvirus. J Virol 75, 3129–3140.[CrossRef] [Google Scholar]
  23. Sun, R., Lin, S. F., Gradoville, L., Yuan, Y., Zhu, F. & Miller, G.(1998). A viral gene that activates lytic cycle expression of Kaposi's sarcoma-associated herpesvirus. Proc Natl Acad Sci U S A 95, 10866–10871.[CrossRef] [Google Scholar]
  24. Tamura, T., Yanai, H., Savitsky, D. & Taniguchi, T.(2008). The IRF family transcription factors in immunity and oncogenesis. Annu Rev Immunol 26, 535–584.[CrossRef] [Google Scholar]
  25. Vieira, J. & O'Hearn, P. M.(2004). Use of the red fluorescent protein as a marker of Kaposi's sarcoma-associated herpesvirus lytic gene expression. Virology 325, 225–240.[CrossRef] [Google Scholar]
  26. Wang, S., Liu, S., Wu, M. H., Geng, Y. & Wood, C.(2001). Identification of a cellular protein that interacts and synergizes with the RTA (ORF50) protein of Kaposi's sarcoma-associated herpesvirus in transcriptional activation. J Virol 75, 11961–11973.[CrossRef] [Google Scholar]
  27. Wang, J., Zhang, J., Zhang, L., Harrington, W., Jr, West, J. T. & Wood, C.(2005). Modulation of human herpesvirus 8/Kaposi's sarcoma-associated herpesvirus replication and transcription activator transactivation by interferon regulatory factor 7. J Virol 79, 2420–2431.[CrossRef] [Google Scholar]
  28. Yu, Y., Wang, S. E. & Hayward, G. S.(2005). The KSHV immediate-early transcription factor RTA encodes ubiquitin E3 ligase activity that targets IRF7 for proteosome-mediated degradation. Immunity 22, 59–70.[CrossRef] [Google Scholar]
  29. Zhang, L. & Pagano, J. S.(1997). IRF-7, a new interferon regulatory factor associated with Epstein–Barr virus latency. Mol Cell Biol 17, 5748–5757. [Google Scholar]
  30. Zhang, L. & Pagano, J. S.(2002). Structure and function of IRF-7. J Interferon Cytokine Res 22, 95–101.[CrossRef] [Google Scholar]
  31. Zhang, J., Wang, J., Wood, C., Xu, D. & Zhang, L.(2005). Kaposi's sarcoma-associated herpesvirus/human herpesvirus 8 replication and transcription activator regulates viral and cellular genes via interferon-stimulated response elements. J Virol 79, 5640–5652.[CrossRef] [Google Scholar]
  32. Ziegelbauer, J., Grundhoff, A. & Ganem, D.(2006). Exploring the DNA binding interactions of the Kaposi's sarcoma-associated herpesvirus lytic switch protein by selective amplification of bound sequences in vitro. J Virol 80, 2958–2967.[CrossRef] [Google Scholar]

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vol. , part 12, pp. 181–187

Primers used for the mutagenesis of IRF-7.

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