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Tax inflicts DNA damage through activation of Nitric Oxide production

Adult T-cell Leukemia-Lymphoma (ATLL) is an aggressive and fatal malignancy of CD4+ T-lymphocytes associated with HTLV-1 infection, and an effective treatment is not yet available. The molecular mechanism underlying ATLL has not been fully elucidated. However, accumulation of genomic instability is believed to be a driving force for leukemogensis. How genomic instability accumulates in HTLV-1 infected cells is currently under intensive investigation. Recently, we found that the HTLV-1 viral oncoprotein, Tax, which is implicated in the chronic inflammatory response, induces DNA Double Strand Breaks (DDSB). Tax is known to activate the key T-cell inflammatory transcription factors, NF-kB, and this activation is critical for the leukemogenic process associated with HTLV-1 infection. Of note, we found that inducible nitric oxide synthase (iNOS), the enzyme that catalyzes the production of nitric oxide (NO) is highly expressed in HTLV-1 and Tax expressing cells. Interestingly, we show that the expression of iNOS is Tax-dependent and specifically requires the classical NF-kB pathway. In addition, IRF-1, the interferon regulatory factor that collaborates with NF-kB transcription factors to activate iNOS expression was also found activated by the JAK/STAT pathway. Our results show a correlation between the number of DDSB and the production of NO in tumors isolated from Tax transgenic mice. We also observed a dramatic reduction of DDSB when NO production was inhibited. Determination of the impact of NO on tumors in an ATLL mouse model will open a new area in the development of alternative strategies for the treatment/prevention of ATLL.

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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. The Creative Commons Public Domain Dedication waiver ( applies to the data made available in this article, unless otherwise stated.

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Baydoun, H.H., Ratner, L. Tax inflicts DNA damage through activation of Nitric Oxide production. Retrovirology 11 (Suppl 1), P107 (2014).

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