Rem lacks activity on heterologous RNA export elements. A. Rem activity on heterologous export elements in Jurkat T cells. Cells were transfected with reporter plasmids containing the indicated response elements described in Figure 1 with or without expression vectors for retroviral export proteins. B. Rem activity on heterologous export elements in HC11 mouse mammary cells. Relative luciferase values in both panels are reported as described in Figure 2.