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

Abstract

We analyzed the TS-2 acute lymphoblastic leukemia (ALL) cell line that contains a t(1;19)(q23;p13.3) but lacks E2A-PBX1 fusion typically present in leukemias with this translocation. 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. MEF2D is a member of the MEF2 family of DNA binding proteins that activate transcription of genes involved in control of muscle cell differentiation, and signaling pathways that mediate response to mitogenic signals and survival of neurons and T-lymphocytes. DAZAP1 is a novel RNA binding protein expressed most abundantly in the testis. 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. MEF2D has been identified as a candidate oncogene in murine retroviral insertional mutagenesis studies. 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.

Cooperative transformation by MEF2D/DAZAP1 and DAZAP1/MEF2D fusion proteins generated by the variant t(1;19) in acute lymphoblastic leukemia

“…14 The location of MEF2D at the breakpoint of a chromosome translocation in human acute lymphoblastic leukemia, 4,5 and the current studies demonstrating potent transforming properties of both resultant MEF2D protein chimeras establish that MEF2D has latent oncogenic properties. Members of MEF2 protein family interact with a variety of other Cooperative transformation by MEF2D/DAZAP1 and DAZAP1/MEF2 V Prima and SP Hunger proteins involved in transcriptional regulation including histone deacetylases, p300 and Cabin1/Cain.…”

“…cDNA fragments encoding human DAZAP1, MEF2D, DAZAP1/ MEF2D and MEF2D/DAZAP1 were FLAG-tagged 5 and cloned into the XhoI site of pMSCVneo or pMSCVhyg vectors (Clontech, Mountain View, CA, USA). A transient-transfection system 8 was used to create retroviruses harboring the DAZAP1 and MEF2D wild-type and fusion cDNAs.…”

“…4,5 MEF2D is a member of the MEF2 family of DNA-binding proteins, which activate transcription of genes involved in control of differentiation and survival of lymphoid, neural and muscle cells. 6 DAZAP1 is a novel RNA-binding protein involved in mRNA processing/trafficking that is expressed most abundantly in testis.…”

MEF2C is activated by multiple mechanisms in a subset of T-acute lymphoblastic leukemia cell lines

“…Expression of both MEF2C and MEF2D occurs in lymphocytes, while that of MEF2C is restricted to B-cells, implying that activation in T-ALL cells may require dysregulation. 43 In pre-B-ALL, t(1;19)(q23;p13) results in the fusion of MEF2D with DAZAP1 shown to be involved in pathogenesis, 44,45 supporting the notion of leukemic potential among MEF2-proteins.…”

Class IIa histone deacetylases: regulating the regulators

“…It is now essential to establish whether alterations of the class IIa HDAC-MEF2 axis occur in these human pathologies. Genetic alterations of MEF2 family members have been linked to cardiovascular diseases (Wang, 2005;Visvikis-Siest and Marteau, 2006) and acute lymphoblastic leukemia (Yuki et al, 2004;Prima et al, 2005). Similarly, alterations of MEF2 transcriptional activity have been implicated in neurodegenerative disorders (Camins et al, 2006) and cardiac hypertrophy (Czubryt and Olson, 2004).…”