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Volume 8 Supplement 2

Frontiers of Retrovirology 2011

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Distinct activities of HTLV-1 Tax1 from HTLV-2 Tax2 play key roles in pathogenesis

While human T cell leukemia virus type 1 (HTLV-1) is an etiological agent of adult T-cell leukemia (ATL), its close relative HTLV-2 is not associated with any leukemia. HTLV-1 and HTLV-2 encode Tax1 and Tax2 proteins, respectively, which are essential for immortalization of T-cells by the respective viruses, thereby persistent infection. Tax1 and Tax2 have more than 75% amino acid similarities, but we show here that Tax1 and Tax2 have multiple distinct activities. Tax1 induced IL-2-independent growth of a T-cell line CTLL-2 more efficiently than Tax2. By contrast, Tax2 immortalized human T-cells in the presence of IL-2 more efficiently than Tax1. These results suggest that HTLV-1 and HTLV-2 have distinct IL-2 requirements to immortalize T-cells. We also found that Tax1 altered cellular oxidative stress response. Arsenite, a pro-oxidant, induced stress granule (SG) formation, which functions as a protective role against oxidant-induced cell damages, but the formation was inhibited by Tax1. We will discuss these findings in terms of the HTLV-1-specific pathogenesis.

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This article is published under license to BioMed Central Ltd. This is an open access article distributed under the terms of the Creative Commons Attribution License (, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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Fujii, M., Takahashi, M., Yoshita, M. et al. Distinct activities of HTLV-1 Tax1 from HTLV-2 Tax2 play key roles in pathogenesis. Retrovirology 8 (Suppl 2), O22 (2011).

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