Activity of HERV-K Rec on a reporter plasmid containing the MMTV RmRE in human and mouse cells. A. Reporter activity in Jurkat T cells. B. Western blotting of Rem and Rec expression in Jurkat cells. Results using antibodies specific for GFP (upper panel) and actin (lower panel) are shown. Size markers are given in kilodaltons. C. Reporter activity in HC11 mouse mammary cells. Values in panels A and C are reported as in Figure 2, except that a RecGFP expression plasmid was used.