A 10-amino acid domain within human T-cell leukemia virus type 1 and type 2 tax protein sequences is responsible for their divergent subcellular distribution.
Human T-cell leukemia virus type 1 and type 2 (HTLV-1/2) are related retroviruses that infect T-lymphocytes. Whereas HTLV-1 infection can cause leukemia, HTLV-2 has not been demonstrated to be the agent of a hematological malignant disease. Nevertheless, the virally encoded Tax-1 and Tax-2 transactivators display a high percentage of similarity. Tax-1 is a shuttling protein that contains a noncanonical nuclear localization signal as well as a nuclear export signal. The presence of the nuclear localization signal and the nuclear export signal domains in the Tax-2 sequence has not been determined. The distribution of Tax-2 in infected cells is not known but has been assumed to be similar to that of Tax-1. By using a Tax-2-specific antibody, we report here that Tax-2 is located predominantly in the cytoplasm of the HTLV-2 immortalized or transformed infected T-cells. These results were confirmed after transient transfection of untagged Tax-1 and Tax-2 constructs, histidine tag Tax1/Tax2, GFP-Tax, and Tax-GFP fusion constructs in several cell lines. We show that this unanticipated localization is not due to a default in the Tax-2 nuclear localization signal functions nor to major differences in Tax-2 versus Tax-1 binding to the IKKgamma/NEMO protein. In addition, we demonstrate that inhibiting the proteasome results in a relocalization of Tax-1 in the cytoplasm, similar to that of Tax-2. By using a series of Tax-1/Tax-2 chimeras, we determined that the minimal domain that is necessary for Tax-2 peculiar distribution encompasses amino acids 90-100. Finally, we show a high correlation between intracellular localization of Tax and their NF-kappaB or CREB transactivating ability.
Unité d'Epidémiologie et Physiopathologie des Virus Oncogènes, Institut Pasteur, 75724 Paris Cedex 15, France. meertens@pasteur.fr
Laurent
L
Meertens
Sébastien
S
Chevalier
Robert
R
Weil
Antoine
A
Gessain
Renaud
R
Mahieux
D000595:Amino Acid Sequence; D000596:Amino Acids / Q000737:chemistry; D000818:Animals; D015153:Blotting, Western; D019556:COS Cells; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism; D017362:Cyclic AMP Response Element-Binding Protein / Q000378:metabolism; D003593:Cytoplasm / Q000378:metabolism; D019084:Fluorescent Antibody Technique, Indirect; D016356:Gene Products, tax / Q000737:chemistry* / Q000378:metabolism; D006367:HeLa Cells; D006639:Histidine / Q000737:chemistry; D015368:Human T-lymphotropic virus 1 / Q000378:metabolism*; D015367:Human T-lymphotropic virus 2 / Q000378:metabolism*; D006801:Humans; D015151:Immunoblotting; D047468:Immunoprecipitation; D008156:Luciferases / Q000378:metabolism; D008969:Molecular Sequence Data; D016328:NF-kappa B / Q000378:metabolism; D019913:Nuclear Localization Signals; D010957:Plasmids / Q000378:metabolism; D017434:Protein Structure, Tertiary; D015398:Signal Transduction; D013601:T-Lymphocytes / Q000378:metabolism; D015533:Transcriptional Activation; D014162:Transfection
D000596:Amino Acids; D017362:Cyclic AMP Response Element-Binding Protein; D016356:Gene Products, tax; D016328:NF-kappa B; D019913:Nuclear Localization Signals; D006639:Histidine; D008156:Luciferases