Comparative analysis of post-translational modifications of HTLV-1 and HTLV-2 Tax proteins and their influence on intracellular localization and gene transactivation

The functional comparison of regulatory proteins Tax-1 and Tax-2 can provide useful information to further understand the differences in pathogenicity between HTLV-1 and HTLV-2. This comparison was made feasible by inserting a Flag epitope at an equivalent position in the carboxy-terminal domains of Tax-1 and Tax-2B that preserved their transcriptional activities and enabled the detection of both proteins with anti-Flag antibody. By using this system we detected ladders of poly-ubiquitinated and poly-sumoylated forms of both proteins. As expected from the critical role of these post-translational modifications for Tax transcriptional activities and its intracellular localization, Tax-1 and Tax-2B activated gene expression via the NF-κB pathway to similar levels and Tax-2B was present in nuclear bodies and in the cytoplasm as previously observed for Tax-1. A series of mutants based on the substitution of the different 14 lysines of internally tagged Tax-2B, have been developed. The modification patterns of these mutants, their transactivating capacity and subcellular localization will be compared to those obtained for the corresponding mutants of Tax-1. This study is addressed to possibly further clarify the molecular mechanisms underlying the different behaviours of HTLV-1 and HTLV-2.