Abstract
E2A-PBX1 is expressed as a result of the t(1;19) chromosomal translocation in nearly 5% of cases of childhood acute lymphoblastic leukemia. The E2A-PBX1 chimeric transcription factor contains the N-terminal transactivation domain of E2A (TCF3) fused to the C-terminal DNA-binding homeodomain of PBX1. While there is no doubt of its oncogenic potential, the mechanisms of E2A-PBX1-mediated pre-B cell transformation and the nature of direct E2A-PBX1 target genes and pathways remain largely unknown. Herein we used chromatin immunoprecipitation assays (ChIP-chip) to identify direct targets of E2A-PBX1, and we used gene expression arrays of siRNA E2A-PBX1-silenced cells to evaluate changes in expression induced by the fusion protein. Combined ChIP-chip and expression data analysis gave rise to direct and functional targets of E2A-PBX1. Further we observe that the set of ChIP-chip identified E2A-PBX1 targets show a collective down-regulation trend in the E2A-PBX1 silenced samples compared to controls suggesting an activating role of this fusion transcription factor. Our data suggest that the expression of the E2A-PBX1 fusion gene interferes with key regulatory pathways and functions of hematopoietic biology. Among these are members of the WNT and apoptosis/cell cycle control pathways, and thus may comprise an essential driving force for the propagation and maintenance of the leukemic phenotype. These findings may also provide evidence of potentially attractive therapeutic targets.
Highlights
E2A-PBX1 is expressed as a result of the t(1;19) chromosomal translocation in nearly 5% of cases of acute lymphoblastic leukemia
While there is no doubt of its oncogenic potential, the mechanisms of E2A-PBX1-mediated pre-B cell transformation and the nature of direct E2A-PBX1 target genes and additional events that complement the fusion oncogene to create full-blown leukemia are still unclear
Using the leukemia cell line (697) expressing E2A-PBX1 and a specific antibody against E2A-PBX1, we performed chromatin ChIP-chip to identify mRNA and miRNA promoters bound by E2A-PBX1
Summary
E2A-PBX1 is expressed as a result of the t(1;19) chromosomal translocation in nearly 5% of cases of acute lymphoblastic leukemia. We employed chromatin immunoprecipitation (ChIP-chip) assays to identify direct targets E2A-PBX1, and we used gene and miRNA expression arrays of siRNA E2A-PBX1-silenced cells to evaluate changes in expression induced by the fusion protein. Pathway analyses of the of E2A-PBX1 direct and functional targets support the WNT pathway as a downstream target of this fusion gene product and present novel insights, including pathways involved in cell cycle control and apoptosis.
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