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Journal of Virology, January 2001, p. 458-468, Vol. 75, No. 1
Division of Hematology/Oncology, Case Western
Reserve University, Cleveland, Ohio 441061;
Department of Biochemistry, Stanford University School of
Medicine, Stanford, California 943052;
Department of Microbiology and Immunology, University of
Oklahoma Health Sciences Center, Oklahoma City, Oklahoma
731903; and Howard Hughes Medical Institute
and Departments of Microbiology and Medicine, University of
California, San Francisco, California 94143-04144
Received 14 June 2000/Accepted 29 September 2000
Kaposi's sarcoma-associated herpesvirus (KSHV), also called human
herpesvirus 8 (HHV-8), is the likely etiological agent of Kaposi's
sarcoma and primary effusion lymphoma. Common to these malignancies is
that tumor cells are latently infected with KSHV. Viral gene expression
is limited to a few genes, one of which is the latency-associated
nuclear antigen (LANA), the product of ORF73. Examination of the
primary sequence of LANA reveals some structural features reminiscent
of transcription factors, leading us to hypothesize that LANA may
regulate viral and cellular transcription during latency. In reporter
gene-based transient transfection assays, we found that LANA can have
either positive or negative effects on gene expression. While
expression of a reporter gene from several synthetic promoters was
increased in the presence of LANA, expression from the human
immunodeficiency virus (HIV) long terminal repeat (LTR)
0022-538X/01/$04.00+0 DOI: 10.1128/JVI.75.1.458-468.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
Modulation of Cellular and Viral Gene Expression by
the Latency-Associated Nuclear Antigen of Kaposi's
Sarcoma-Associated Herpesvirus
and from
NF-
B-dependent reporter genes
was reduced by LANA expression. In
addition, the promoter of KSHV ORF73 itself is activated up to 5.5-fold
by LANA. This autoregulation may be important in tumorigenesis, because two other genes (v-cyclin and v-FLIP) with likely roles in cell growth
and survival are also controlled by this element. To identify cellular
genes influenced by LANA, we employed cDNA array-based expression
profiling. Six known genes (and nine expressed sequence tags) were
found to be upregulated in LANA-expressing cell lines. One of these,
Staf-50, is known to inhibit expression from the HIV LTR; most of the
other known genes are interferon inducible, although the interferon
genes themselves were not induced by LANA. These data demonstrate that
LANA expression has effects on cellular and viral gene expression. We
suggest that, whether direct or indirect in origin, these effects may
play important roles in the pathobiology of KSHV infection.
*
Corresponding author. Mailing address: Division of
Hematology/Oncology, Case Western Reserve University, 10900 Euclid
Ave., Cleveland, OH 44106. Phone: (216) 368-1190. Fax: (216)
368-1166. E-mail: rfr3{at}po.cwru.edu.
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