HTLV Rex1 and 2 activity on the MMTV RmRE in mouse mammary cells. A. Reporter activity in HC11 mouse mammary cells. Values are reported as in Figure 2, except that Rex1GFP and Rex2GFP expression plasmids were used. B. Western blots of extracts from Rex and Rem-transfected HC11 cells. A GFP-related band is observed in this blot (asterisk; lanes 1 and 5), but the major band is not visible in this portion of the gel (upper panel). Similar levels of Rem, Rex1 and Rex2 fusion proteins are observed using the GFP-specific antibody. Incubation with an actin-specific antibody revealed similar protein loading in each lane (lower panel). Size markers are given in kilodaltons.