Destabilization of AETFC through C/EBPalpha-mediated repression of LYL1 contributes to t(8;21) leukemic cell differentiation

In t(8;21) leukemic cells, the leukemogenic fusion protein AML1-ETO is stabilized and functions through the AML1-ETO-containing transcription factor complex (AETFC). Destabilization of AETFC thus provides a strategy to target AML1-ETO. In this study, we found that AETFC can be destabilized by a specific mechanism involving a direct repression of the core component LYL1 by C/EBPalpha at transcriptional level. We performed a ChIP-seq analysis of the genome-wide occupancy of C/EBPalpha and identifeid a -1 kb C/EBPalpha-binding site in the LYL1 locus that mediate this repression. As LYL1 acts as a linker between the AML1-ETO-E and LMO2-LDB1 parts of AETFC, depletion of LYL1 causes a destabilization of AETFC, which increases susceptibility of the leukemic cells to differentiation. Our results have provided a novel mechanism by which C/EBPalpha can directly destabilize AETFC, and have identified LYL1 as a new therapeutic target for treatment of t(8;21) leukemia. Since the expression of C/EBPalpha in the AML1-ETO-expressing Kasumi-1 cells is very low, we overexpressed an HA-tagged C/EBPalpha in the cells and performed the ChIP-seq with an anti-HA antibody. We also performed RNA-seq analysis of the C/EBPalpha-overexpressing Kasumi-1 cells and the control cells transduced with the MIGR1 vector.