Human T cell leukemia virus type I (HTLV-I) is linked to the genesis of adult T cell leukemia (ATL), an aggressive CD4+ T cell malignancy. Tax is an oncoprotein encoded by the HTLV-I genome that regulates viral and cellular gene expression. Tax promotes cell transformation, in part, by activating the NF-kB/Rel transcription factor family. Tax requires NF-kB for the immortalization of primary T cells and HTLV-I transformed cells are dependent on NF-kB for their survival, thereby providing a strong rationale for studying the mechanisms used by Tax to activate NF-kB. Tax activates NF-kB by promoting persistent IkB kinase (IKK) activation although the mechanisms are poorly understood. Our supporting studies indicate that polyubiquitination is a key post- translational regulator of Tax activation of NF-kB. Tax activation of NF-kB correlates with ubiquitin-dependent relocalization of IKK to the Golgi apparatus. Tax is polyubiquitinated via Lys 63-linked ubiquitin chains and requires the ubiquitin conjugating enzyme Ubc13 for Tax ubiquitination and NF-kB activation. Ubiquitination of Tax does not promote its degradation, but rather regulates its interaction with the IKK regulatory subunit IKKg. In addition, we have determined that the Tax interacting cellular protein TAX1BP1 is a key negative regulator of cytokine-mediated NF-kB signaling by functioning as an essential subunit for the ubiquitin-editing enzyme A20. We hypothesize that Tax targets TAX1BP1 as part of a mechanism to promote persistent NF-kB activation. In this proposal, we will further investigate how ubiquitination regulates the targeting of Tax and IKK into the Golgi. We will also further delineate the requirements and the identification of host factors regulating Tax ubiquitination. Finally, we will determine the mechanisms used by Tax to inactivate TAX1BP1 and the A20 ubiquitin-editing complex. Our objectives for this proposal will be satisfied by completion of the following specific aims: (1) Determine the mechanisms of Tax-mediated relocalization of IKK;(2) investigate the molecular determinants of Tax ubiquitination and NF-kB activation and (3) determine the role of Tax binding to TAX1BP1 in NF-kB activation. These studies will shed light on how a retroviral oncoprotein usurps host ubiquitination/deubiquitination machinery to persistently activate transcription factors that promote cell transformation.

Public Health Relevance

The HTLV-I Tax oncoprotein is a potent activator of the NF-kB/Rel transcription factor family. Tax requires NF-kB for the immortalization of T cells, and NF-kB is also required for the survival of HTLV-1 transformed cell lines. The focus of the proposal is to determine the molecular mechanisms used by Tax to activate NF-kB, specifically we will further establish the determinants of Tax ubiquitination and examine the role of Tax interaction with the cellular protein TAX1BP1.

Agency
National Institute of Health (NIH)
Institute
National Cancer Institute (NCI)
Type
Research Project (R01)
Project #
5R01CA135362-05
Application #
8446292
Study Section
Cancer Molecular Pathobiology Study Section (CAMP)
Program Officer
Read-Connole, Elizabeth Lee
Project Start
2009-04-01
Project End
2015-01-31
Budget Start
2013-02-01
Budget End
2015-01-31
Support Year
5
Fiscal Year
2013
Total Cost
$245,201
Indirect Cost
$93,842
Name
Johns Hopkins University
Department
Internal Medicine/Medicine
Type
Schools of Medicine
DUNS #
001910777
City
Baltimore
State
MD
Country
United States
Zip Code
21218
Lavorgna, Alfonso; Matsuoka, Masao; Harhaj, Edward William (2014) A critical role for IL-17RB signaling in HTLV-1 tax-induced NF-?B activation and T-cell transformation. PLoS Pathog 10:e1004418
Choi, Young Bong; Harhaj, Edward William (2014) HTLV-1 tax stabilizes MCL-1 via TRAF6-dependent K63-linked polyubiquitination to promote cell survival and transformation. PLoS Pathog 10:e1004458
Lavorgna, Alfonso; Harhaj, Edward William (2014) Regulation of HTLV-1 tax stability, cellular trafficking and NF-?B activation by the ubiquitin-proteasome pathway. Viruses 6:3925-43
Gao, Linlin; Harhaj, Edward William (2013) HSP90 protects the human T-cell leukemia virus type 1 (HTLV-1) tax oncoprotein from proteasomal degradation to support NF-*B activation and HTLV-1 replication. J Virol 87:13640-54
Lavorgna, Alfonso; Harhaj, Edward W (2013) Is there a role for ubiquitin or SUMO in human T-cell leukemia virus type 2 Tax-induced NF-*B activation? Future Virol 8:223-227
Shembade, Noula; Harhaj, Edward W (2012) Regulation of NF-?B signaling by the A20 deubiquitinase. Cell Mol Immunol 9:123-30
Harhaj, Edward W; Dixit, Vishva M (2012) Regulation of NF-*B by deubiquitinases. Immunol Rev 246:107-24
Lavorgna, Alfonso; Harhaj, Edward W (2012) An RNA interference screen identifies the Deubiquitinase STAMBPL1 as a critical regulator of human T-cell leukemia virus type 1 tax nuclear export and NF-?B activation. J Virol 86:3357-69
Lavorgna, Alfonso; Harhaj, Edward W (2012) EBV LMP1: New and shared pathways to NF-ýýB activation. Proc Natl Acad Sci U S A 109:2188-9
Charoenthongtrakul, Soratree; Zhou, Qinjie; Shembade, Noula et al. (2011) Human T cell leukemia virus type 1 Tax inhibits innate antiviral signaling via NF-kappaB-dependent induction of SOCS1. J Virol 85:6955-62

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