KMT2A and leukemia: Indeed, the active P-TEFb-Brd4 complex has been linked to AML and CML (Dawson et al., 2011; Mertz et al., 2011; Zuber et al., 2011; Herrmann et al., 2012; Winter et al., 2012), while multiple SEC components are direct targets of MLL-fusion proteins that are linked to various forms of leukemia (Lin et al., 2010; Yokoyama et al., 2010).