Physical and functional interaction between the human T-cell lymphotropic virus type 1 Tax1 protein and the CCAAT binding protein NF-Y.
Tax1, a potent activator of human T-cell lymphotropic virus type 1 (HTLV-1) transcription, has been shown to modulate expression of many cellular genes. Tax1 does not bind DNA directly but regulates transcription through protein-protein interactions with sequence-specific transcription factors. Using the yeast two-hybrid system to screen for proteins which interact with Tax1, we isolated the B subunit of the CCAAT binding protein NF-Y from a HeLa cDNA library. The interaction of Tax1 with NF-YB was specific in that NF-YB did not interact with a variety of other transcription factors, including human immunodeficiency virus Tat, human papillomavirus E6, and Bicoid, or with the M7 (amino acids 29CP-AS) Tax1 mutant. However, NF-YB did interact with the C-terminal Tax1 mutants M22 (130TL-AS) and M47 (319LL-RS). We also show that in vitro-translated NF-YB specifically bound to a glutathione S-transferase-Tax1 fusion protein. Further, Tax1 coimmunoprecipitated with NF-Y from nuclear extracts of HTLV-1-transformed cells, providing evidence for in vivo interaction of Tax1 and NF-YB. We further demonstrate that Tax1 specifically activated the NF-Y-responsive DQbeta promoter, as well as a minimal promoter which contains only the Y-box element. In addition, mutation of the Y-box element alone abrogated Tax1-mediated activation. Taken together, these data indicate that Tax1 interacts with NF-Y through the B subunit and that this interaction results in activation of the major histocompatibility complex class II promoter. Through activation of this and other NF-Y driven promoters, the Tax1-NF-Y interaction may play a critical role in causing cellular transformation and HTLV-1 pathogenesis.
Pise-Masison
C A
CA
Laboratory of Molecular Virology, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892-5055, USA.
Dittmer
J
J
Clemens
K E
KE
Brady
J N
JN
D022762:CCAAT-Enhancer-Binding Proteins; D002457:Cell Extracts; D002461:Cell Line, Transformed; D002467:Cell Nucleus; D003001:Cloning, Molecular; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D015967:Gene Expression Regulation, Viral / Q000502:physiology; D016356:Gene Products, tax / Q000235:genetics / Q000378:metabolism*; D005802:Genes, MHC Class II / Q000235:genetics*; D006683:HLA-DQ Antigens / Q000235:genetics; D059866:HLA-DQ beta-Chains; D006367:HeLa Cells; D015368:Human T-lymphotropic virus 1 / Q000235:genetics*; D006801:Humans; D009154:Mutation; D011233:Precipitin Tests; D011401:Promoter Regions, Genetic / Q000235:genetics; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D013601:T-Lymphocytes; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*
D022762:CCAAT-Enhancer-Binding Proteins; D002457:Cell Extracts; D004268:DNA-Binding Proteins; D016356:Gene Products, tax; D006683:HLA-DQ Antigens; D059866:HLA-DQ beta-Chains; C057615:HLA-DQbeta antigen; D011993:Recombinant Fusion Proteins; D014157:Transcription Factors