F5 and leukemia: This inhibitory mechanism is distinct from previously reported inhibitors that specifically inhibit Tas-dependent transcriptional activation, including nuclear factor I (NFI) [44] that inhibits Tas-dependent transcription by binding to the FV IP promoter as well as N-Myc interactor (Nmi) [45], p53-induced RING-H2 (PIRH2) [46], and promyelocytic leukaemia (PML) [47] that act by binding to and sequestering Tas.