Mutational analysis of human T-cell leukemia virus type 2 Tax

Abstract

A mutational analysis of human T-cell leukemia virus type 2 (HTLV-2) Tax (Tax-2) was performed to identify regions within Tax-2 important for activation of promoters through the CREB/ATF or NF-B/Rel signaling pathway. Tax-2 mutations within the putative zinc-binding region as well as mutations at the carboxy terminus disrupted CREB/ATF transactivation. A single mutation within the central proline-rich region of Tax-2 disrupted the transactivation of the NF-B/Rel pathway. Surprisingly, this mutation, which is thought to be in a separate activation domain, was suppressed by mutations within or around the putative zinc-binding region, suggesting an interaction between these two regions. These analyses indicate that the functional regions or domains important for transactivation through the CREB/ATF or NF-B/Rel signaling pathway are similar, but not identical, in Tax-1 and Tax-2. Identification of these distinct Tax-2 mutants should facilitate comparative biological studies of HTLV-1 and HTLV-2 and ultimately lead to the determination of the functional importance of Tax transacting capacities in T-lymphocyte transformation by HTLV.

Human T cell leukaemia virus type 2 tax protein mediates CC-chemokine expression in peripheral blood mononuclear cells via the nuclear factor kappa B canonical pathway

“…These results are important, as the entire Tax2 protein or Tax2 fragments bearing NF-κB domains may, potentially, be employed as immunomodulators to induce the production of anti-viral CC-chemokines. These results will assist future in-vitro work testing smaller Tax2-derived peptides [28,29] that may lead eventually to immunotherapeutic studies in animal models.…”

“…In this study the relative potency of the amino-and -carboxy terminal segments of Tax2A containing NF-κB binding domains [28,29] was compared to the entire Tax2A protein. Both Tax2A/1-198 and Tax2A/135-331 fragments induced the phosphorylation of p65/RelA and stimulated CC-chemokine secretion in PBMCs.…”

“…Recombinant Tax1 and Tax2A (subtype A) proteins were purified as described recently in detail [24,25]. Truncated Tax2A/NH2term-His tagged sequence aa [28,29] were subcloned from PET29a-Tax2-H6 [30] to pQE-30 (Amp-resistant) vector and transformed into the Esherichia coli BL21(DE3) strain (subcloning generation and protein production serviced by Promab Biotechnologies, Inc., Richmond, CA, USA). An extract was prepared in an identical manner from E. coli cells containing the empty vector for use as a mock control.…”

“…Tax1 and Tax2A recombinant proteins were assessed for their potential to activate the p65/RelA subunit, which is a well-established indicator of the canonical NF-κB pathway [34], a rapid-acting primary transcription factor. We also employed Tax2A/1-198 and Tax2A/135-331 recombinant Tax2A fragments containing NF-κB domains [28,29] to evaluate their potential to activate the NF-κB pathway compared to the entire Tax2A protein. Treated cells were immunolabelled for the detection of phosphorylated p65/ RelA by immunofluorescence.…”

tax and rex Sequences of Bovine Leukaemia Virus from Globally Diverse Isolates: Rex Amino Acid Sequence more Variable than Tax

“…Within the first 30 amino acids of Rex, which correspond with the first 21 amino acids of Tax, very little sequence variation can be seen. The first 30 amino acids of the HTLV-I Tax protein correspond to a cyclic AMP response element binding protein (CREB)-binding domain and a nuclear localization signal (Ross et al, 1997). Although the nucleotide sequences of BLV and HTLV-I are quite different, the Tax proteins of each virus function in a similar way (Coffin, 1996).…”