Transforms host T-cells, inducing T-cell lymphomia in the host. Activates at least SRC and LCK tyrosines kinases, thereby activating signaling pathway transforming host T-cells. Human T-cells transformed ex vivo display a IL2 indenpendent growth phenotype. Homodimer. Binds SH3 domain of host LYN, HCK, LCK, SRC, FYN or YES. When tyrosine-phosphorylated, binds to the SH2 domain of host LCK, SRC, or FYN. Associated with plasma membrane, presumably via its putative transmembrane domain. The SH3B/LBD1 (SH3-binding) region binds LCK SH3 domain and CSKH (C-terminal Src-related kinase homology) region binds the kinase domains of LCK. Both motif are required to activate LCK (By similarity). Phosphorylated by host LCK, SRC and less efficiently by FYN.