TEL-AML1 is an oncogenic fusion protein associated with childhood pre-B acute lymphoblastic leukaemia. From published microarray datasets we identified the Rho Guanine Nucleotide Exchange Factor (RhoGEF) Asef to be associated with TEL-AML1 leukaemia. However, the Asef gene is not a direct target of TEL-AML1 transcriptional control. Forced expression of Asef in vitro induced and maintained proliferation of haemaopoietic progenitor cells and co-operated with TEL-AML1 greatly to enhance proliferation and haemopoietic colony size. In haemopoietic transplantation reconstitution assays Asef and TEL-AML1 together failed to induce a leukaemic phenotype.
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