The latency-associated nuclear antigen of Kaposi's sarcoma-associated herpesvirus manipulates the activity of glycogen synthase kinase-3beta.
The latency-associated nuclear antigen (LANA) of Kaposi's sarcoma-associated herpesvirus (KSHV) is expressed in all KSHV-associated malignancies. LANA is essential for replication and maintenance of the viral episomes during latent infection. However, LANA also has a transcriptional regulatory role and can affect gene expression both positively and negatively. A previously performed yeast two-hybrid screen identified glycogen synthase kinase 3 (GSK-3) as a LANA-interacting protein. Interaction with both GSK-3alpha and GSK-3beta was confirmed in transfected cells with coprecipitation assays. GSK-3beta also interacted with the herpesvirus saimiri homolog ORF73. GSK-3beta is an intermediate in the Wnt signaling pathway and a negative regulator of beta-catenin. In transfected cells, LANA was shown to overcome GSK-3beta-mediated degradation of beta-catenin. Examination of primary effusion lymphoma (PEL) cells found increased levels of beta-catenin relative to KSHV-negative B cells, and this translated into increased activity of a beta-catenin-responsive reporter containing Tcf/Lef binding sites. In tetradecanoyl phorbol acetate-treated PEL cells, loss of LANA expression correlated temporally with loss of detectable beta-catenin. LANA was found to alter the intracellular distribution of GSK-3beta so that nuclear GSK-3beta was more readily detectable in the presence of LANA. Mapping experiments with coimmunoprecipitation assays revealed that both N-terminal and C-terminal LANA sequences were required for efficient GSK-3beta interaction. LANA mutants that were defective for GSK-3beta interaction were unable to mediate GSK-3beta relocalization or activate a beta-catenin-responsive Tcf-luciferase reporter. This study identified manipulation of GSK-3beta activity as a mechanism by which LANA may modify transcriptional activity and contribute to the phenotype of primary effusion lymphoma.
Fujimuro
Masahiro
M
Viral Oncology Program, Sidney Kimmel Cancer Center, Johns Hopkins School of Medicine, 1650 Orleans Street, Baltimore, MD 21231, USA.
Hayward
S Diane
SD
D000595:Amino Acid Sequence; D000956:Antigens, Viral; D015153:Blotting, Western; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism; D003598:Cytoskeletal Proteins / Q000378:metabolism; D015971:Gene Expression Regulation, Enzymologic; D038362:Glycogen Synthase Kinase 3 / Q000378:metabolism*; D000071679:Glycogen Synthase Kinase 3 beta; D019288:Herpesvirus 8, Human / Q000472:pathogenicity*; D006801:Humans; D016393:Lymphoma, B-Cell / Q000821:virology; D008969:Molecular Sequence Data; D009154:Mutation; D009687:Nuclear Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011233:Precipitin Tests; D016415:Sequence Alignment; D015534:Trans-Activators / Q000378:metabolism; D014407:Tumor Cells, Cultured; D051176:beta Catenin
D000956:Antigens, Viral; C495270:CTNNB1 protein, human; D003598:Cytoskeletal Proteins; D009687:Nuclear Proteins; D015534:Trans-Activators; D051176:beta Catenin; C109540:latency-associated nuclear antigen; C000605506:GSK3B protein, human; D000071679:Glycogen Synthase Kinase 3 beta; D038362:Glycogen Synthase Kinase 3