Plays a critical role in virus induced T-cell transformation. Binds to T-cell-specific tyrosine kinase LCK SH2 and SH3 domains, thereby activating its kinase activity. Once phosphorylated by host LCK, forms a complex with at least STAT 1 and 3, resulting on the phosphorylation of STAT3 and presumably STAT1, and their migration into the nucleus to induce transcription of target genes. Stimulates host ILF3/NF-AT-90 activity. Association with host NXF1/TAP transduces the signal up-regulating surface expression of adhesion molecules as well as activating NF-kappa-B activity. Acts synergistically with StpC to stimulate NF-kappa-B activity and interleukin-2 gene expression. Activation of NF-kappa-B protects lymphocytes from apoptosis, thereby facilitating viral induced cell transformation. May cause down-regulation of host LCK and cell apoptosis when stably overexpressed ex vivo. Interaction with WDR48 induce degradation of T-cell receptor in a lysosome-dependent fashion, when both proteins are overexpressed. The biological effect of this interaction remains controversial since no T-cell receptor degradation is observed in infected cells.