PRMT1 and leukemia: To investigate whether Prmt1 is required for not only initiation (Figure 1A) but also maintenance of the leukemic transformation, we transduced MLL-GAS7 full-blown leukemia cells from primary transplanted mice (So et al., 2003b) with lentivirus co-expressing a GFP marker and Prmt1 shRNA or a scramble control for in vitro and in vivo transformation assays.