Poster Presentation 16th Asian Conference on Transcription 2019

E2A-PBX1 functions as a coactivator for RUNX1 in acute lymphoblastic leukemia (1155)

Wen-Chieh Pi 1 , Jun Wang 2 , Miho Shimada 3 , Huimin Geng 4 , Yu-Ling Lee 3 , Dongxu Li 2 , Gang G. Wang 2 , Robert G. Roeder 3 , Wei-Yi Chen 1
  1. Institute of Biochemistry and Molecular Biology, National Yang-Ming University, Taipei, Taiwan
  2. Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill School of Medicine, Chapel Hill, NC, USA
  3. Laboratory of Biochemistry and Molecular Biology, The Rockefeller University, New York, NY, USA
  4. Laboratory Medicine, UCSF School of Medicine, San Francisco, CA, USA

E2A, abasic helix-loop-helix (bHLH) transcription factor, plays a crucial role in determining tissue-specific cell fate, including differentiation of B cell lineages. In 5% of childhood acute lymphoblastic leukemia (ALL), the t(1,19) chromosomal translocation specifically targets the E2Agene and produces an oncogenic E2A-PBX1 fusion protein. While previous studies have demonstrated oncogenic functions of E2A-PBX1 in cell and animal models, the E2A-PBX1-enforcedĀ cistrome, the E2A-PBX1 interactome, and related mechanisms underlying leukemogenesis remain unclear. Here, by unbiased genomic profiling approaches, we identify the direct target sites of E2A-PBX1 in t(1,19)-positive pre-B ALL cells and show that, compared to normal E2A, E2A-PBX1 preferentially binds to a subset of gene loci co-bound by RUNX1 and gene-activating machineries (p300, MED1, and H3K27 acetylation). Using biochemical analyses, we further document a direct interaction between E2A-PBX1 and RUNX1 and show that E2A-PBX1 binding to gene enhancers is dependent on RUNX1, but not the DNA-binding activity harbored within the PBX1 homeodomain of E2A-PBX1. Transcriptome analyses and cell transformation assays further establish a significant RUNX1 requirement for E2A-PBX1-mediated target gene activation and leukemogenesis. Notably, the RUNX1 locus itself is also directly activated by E2A-PBX1, indicating a multilayered interplay between E2A-PBX1 and RUNX1. Collectively, our study provides the first unbiased profiling of the E2A-PBX1 cistrome in pre-B ALL cells and reveals a previously unappreciated pathway in which E2A-PBX1 acts in concert with RUNX1 to enforce transcriptome alterations for the development of pre-B ALL.