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Journal of Virology, September 2001, p. 7882-7892, Vol. 75, No. 17
Division of Hematology/Oncology and
Department of Molecular Biology and Microbiology, Case Western Reserve
University, Cleveland, Ohio 44106
Received 9 March 2001/Accepted 18 May 2001
Kaposi's sarcoma-associated herpesvirus (KSHV) is associated with
Kaposi's sarcoma, primary effusion lymphoma, and multicentric Castleman's disease. The latency-associated nuclear antigen (LANA) is
highly expressed in these malignancies and has been shown to play an
important role in episomal maintenance, presumably by binding to a
putative oriP. In addition, LANA modulates cellular and viral gene
expression and interacts with the cellular tumor suppressors p53 and
retinoblastoma suppressor protein. Many of these features are
reminiscent of Epstein-Barr virus nuclear antigens (EBNAs), a family of
six proteins expressed during latency. EBNA-1 is required for episome
maintenance, binds to oriP, and strongly activates transcription from
two promoters, including its own. We have previously shown that LANA
can transactivate its own promoter and therefore asked whether LANA,
like EBNA-1, activates transcription by direct binding to DNA. By using
recombinant LANA expressed from vaccinia virus vectors for
electrophoretic mobility shift assays, we found that LANA does not bind
to its own promoter. In contrast, LANA binds specifically to sequences
containing an imperfect 20-bp palindrome in the terminal repeat (TR) of
KSHV. We further show that the C-terminal domain of LANA is sufficient for site-specific DNA binding. Unlike EBNA-1, which activates transcription through binding of oriP, we found that LANA inhibits transcription from a single TR binding site. A multimerized TR as found
in the viral genome results in strong transcriptional suppression when
linked to a heterologous promoter. These data suggest that LANA,
although fulfilling functions similar to those of EBNA-1, does so by
very different mechanisms.
0022-538X/01/$04.00+0 DOI: 10.1128/JVI.75.17.7882-7892.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
DNA Binding and Modulation of Gene Expression by
the Latency-Associated Nuclear Antigen of Kaposi's
Sarcoma-Associated Herpesvirus
*
Corresponding author. Mailing address: Division of
Hematology/Oncology, Case Western Reserve University, Cleveland, OH
44106. Phone: (216) 368-1190. Fax: (216) 368-1166. E-mail:
rfr3{at}po.cwru.edu.
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