We previously identified TEL/ARG as a novel fusion transcript consisting of the oligomerization domain of TEL and the kinase domain of ARG, in a case of acute myeloid leukemia. We report here the existence of an alternatively spliced TEL/ARG transcript lacking part of a F-actin binding domain of ARG, and the phenotype of TEL/ARG expressing 293T cells. In 293T cells, both TEL/ARG forms co-localized with the cellular beta-actin and were associated with a morphologic change of the cells, consisting in cell rounding and detachment from the tissue culture plastic. We identified the Rho inhibitor p190RhoGAP, a critical regulator of cellular adhesion, as a target of the aberrant kinase.