We found that the t(1;19) in TS-2 fuses the 19p13 gene DAZAP1 (Deleted in Azoospermia-Associated Protein 1) to the 1q23 gene MEF2D (Myocyte Enhancer Factor 2D), leading to expression of reciprocal in-frame DAZAP1/MEF2D and MEF2D/DAZAP1 transcripts.     ///    Cloning and functional characterization of MEF2D/DAZAP1 and DAZAP1/MEF2D fusion proteins created by a variant t(1;19)(q23;p13.3) in acute lymphoblastic leukemia..     ///    We demonstrate that MEF2D/DAZAP1 binds avidly and specifically to DNA in a manner indistinguishable from that of native MEF2D and is a substantially more potent transcriptional activator than MEF2D.     ///    We also show that DAZAP1/MEF2D is a sequence-specific RNA-binding protein.     ///    Our data implicate MEF2D in human cancer and suggest that MEF2D/DAZAP1 and/or DAZAP1/MEF2D contribute to leukemogenesis by altering signaling pathways normally regulated by wild-type MEF2D and DAZAP1.. 