Forgot your Password

If you have forgotten your password, please enter your account email below and we will reset your password and email you the new password.


Login to SciCrunch


Register an Account

Delete Saved Search

Are you sure you want to delete this saved search?


NIF LinkOut Portal


Human T-cell leukemia virus type 1 Tax induction of NF-kappaB involves activation of the IkappaB kinase alpha (IKKalpha) and IKKbeta cellular kinases.

Geleziunas R, Ferrell S, Lin X, Mu Y, Cunningham ET, Grant M, Connelly MA, Hambor JE, Marcu KB, Greene WC
Molecular and cellular biology


Tax corresponds to a 40-kDa transforming protein from the pathogenic retrovirus human T-cell leukemia virus type 1 (HTLV-1) that activates nuclear expression of the NF-kappaB/Rel family of transcription factors by an unknown mechanism. Tax expression promotes N-terminal phosphorylation and degradation of IkappaB alpha, a principal cytoplasmic inhibitor of NF-kappaB. Our studies now demonstrate that HTLV-1 Tax activates the recently identified cellular kinases IkappaB kinase alpha (IKKalpha) and IKKbeta, which normally phosphorylate IkappaB alpha on both of its N-terminal regulatory serines in response to tumor necrosis factor alpha (TNF-alpha) and interleukin-1 (IL-1) stimulation. In contrast, a mutant of Tax termed M22, which does not induce NF-kappaB, fails to activate either IKKalpha or IKKbeta. Furthermore, endogenous IKK enzymatic activity was significantly elevated in HTLV-1-infected and Tax-expressing T-cell lines. Transfection of kinase-deficient mutants of IKKalpha and IKKbeta into either human Jurkat T or 293 cells also inhibits NF-kappaB-dependent reporter gene expression induced by Tax. Similarly, a kinase-deficient mutant of NIK (NF-kappaB-inducing kinase), which represents an upstream kinase in the TNF-alpha and IL-1 signaling pathways leading to IKKalpha and IKKbeta activation, blocks Tax induction of NF-kappaB. However, plasma membrane-proximal elements in these proinflammatory cytokine pathways are apparently not involved since dominant negative mutants of the TRAF2 and TRAF6 adaptors, which effectively block signaling through the cytoplasmic tails of the TNF-alpha and IL-1 receptors, respectively, do not inhibit Tax induction of NF-kappaB. Together, these studies demonstrate that HTLV-1 Tax exploits a distal part of the proinflammatory cytokine signaling cascade leading to induction of NF-kappaB. The pathological alteration of this cytokine pathway leading to NF-kappaB activation by Tax may play a central role in HTLV-1-mediated transformation of human T cells, clinically manifested as the adult T-cell leukemia.

  1. Welcome

    Welcome to NIF. Explore available research resources: data, tools and materials, from across the web

  2. Community Resources

    Search for resources specially selected for NIF community

  3. More Resources

    Search across hundreds of additional biomedical databases

  4. Literature

    Search Pub Med abstracts and full text from PubMed Central

  5. Insert your Query

    Enter your search terms here and hit return. Search results for the selected tab will be returned.

  6. Join the Community

    Click here to login or register and join this community.

  7. Categories

    Narrow your search by selecting a category. For additional help in searching, view our tutorials.

  8. Query Info

    Displays the total number of search results. Provides additional information on search terms, e.g., automated query expansions, and any included categories or facets. Expansions, filters and facets can be removed by clicking on the X. Clicking on the + restores them.

  9. Search Results

    Displays individual records and a brief description. Click on the icons below each record to explore additional display options.