Identification of TAZ as a binding partner of the polyomavirus T antigens.
A polyomavirus mutant isolated by the tumor host range selection procedure (19) has a three-amino-acid deletion (Delta2-4) in the common N terminus of the T antigens. To search for a cellular protein bound by wild-type but not the mutant T antigen(s), a yeast two-hybrid screen of a mouse embryo cDNA library was carried out with a bait of wild-type small T antigen (sT) fused N terminally to the DNA-binding domain of Gal4. TAZ, a transcriptional coactivator with a WW domain and PDZ-binding motif (17), was identified as a binding partner. TAZ bound in vivo to all three T antigens with different apparent affinities estimated as 1:7:100 (large T antigen [lT]:middle T antigen [mT]:sT). The Delta2-4 mutant T antigens showed no detectable binding. The sT and mT of the host range transformation-defective (hr-t) mutant NG59 with an alteration in the common sT/mT region (179 D-->NI) and a normal N terminus also failed to bind TAZ, while the unaltered lT bound but with reduced affinity compared to that seen in a wild-type virus infection. The WW domain but not the PDZ-binding motif of TAZ was essential for T antigen binding. The Delta2-4 mutant was defective in viral DNA replication. Forced overexpression of TAZ blocked wild-type DNA replication in a manner dependent on the binding site for the polyomavirus enhancer-binding protein 2alpha. Wild-type polyomavirus T antigens effectively block transactivation by TAZ. The functional significance of TAZ interactions with polyomavirus T antigens is discussed.
Tian
Yu
Y
Department of Pathology, Harvard Medical School, 77 Louis Pasteur Ave., Boston, MA 02115, USA.
Li
Dawei
D
Dahl
Jean
J
You
John
J
Benjamin
Thomas
T
D048948:14-3-3 Proteins / Q000378:metabolism; D021581:Active Transport, Cell Nucleus; D000217:Acyltransferases; D000818:Animals; D000957:Antigens, Viral, Tumor / Q000378:metabolism*; D001665:Binding Sites; D004261:DNA Replication; D051379:Mice; D041681:NIH 3T3 Cells; D011120:Polyomavirus / Q000276:immunology*; D011506:Proteins / Q000378:metabolism*; D014157:Transcription Factors / Q000378:metabolism*; D015533:Transcriptional Activation
D048948:14-3-3 Proteins; D000957:Antigens, Viral, Tumor; D011506:Proteins; D014157:Transcription Factors; D000217:Acyltransferases; C486363:tafazzin protein, mouse