Journal of Virology, August 2001, p. 6894-6900, Vol. 75, No. 15
0022-538X/01/$04.00+0 DOI: 10.1128/JVI.75.15.6894-6900.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
Department of Microbiology, Osaka University Medical School, Suita, Osaka 565-0871,1 and Department of Microbiology, Hyogo Medical College, Nishinomiya, Hyogo 663-8501,2 Japan
Received 2 January 2001/Accepted 4 May 2001
The expression of the Kaposi's sarcoma-associated herpesvirus (KSHV) open reading frame 50 (ORF50) protein, Lyta (lytic transactivator), marks the switch from latent KSHV infection to the lytic phase. ORF50/Lyta upregulates several target KSHV genes, such as K8 (K-bZip), K9 (vIRF1), and ORF57, finally leading to the production of mature viruses. The auto-upregulation of ORF50/Lyta is thought to be an important mechanism for efficient lytic viral replication. In this study, we focused on this autoregulation and identified the promoter element required for it. An electrophoretic mobility shift assay indicated that the octamer-binding protein 1 (Oct-1) bound to this element. Mutations in the octamer-binding motif resulted in refractoriness of the ORF50/Lyta promoter to transactivation by ORF50/Lyta, and Oct-1 expression enhanced this transactivation. These results suggest that the autoregulation of ORF50/Lyta is mediated by Oct-1.
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