CBFß-SMMHC-driven leukemogenesis requires enhanced RUNX1-DNA binding affinity in mice

The leukemia fusion gene CBFB-MYH11 requires RUNX1 for leukemogenesis, but the underlying mechanism is unclear. By in vitro studies, we found that CBFß-SMMHC, the chimeric protein encoded by CBFB-MYH11, could enhance the binding affinity between RUNX1 and its target DNA. Increased RUNX1-DNA binding was also observed in myeloid progenitor cells from mice expressing CBFß-SMMHC. Moreover, only CBFß-SMMHC variants able to enhance the DNA binding affinity by RUNX1 could induce leukemia in mouse models. Significant transcriptomic changes, affecting genes associated with inflammatory response and target genes of CBFA2T3, were observed in mice expressing leukemogenic CBFß-SMMHC variants. Finally, we show that CBFß-SMMHC could not induce leukemia in mice with a Runx1-R188Q mutation, which reduces RUNX1 DNA binding but not affecting its interaction with CBFß-SMMHC or its sequestration to cytoplasm by CBFß-SMMHC. Our data suggest that enhancing RUNX1-target DNA binding affinity is an important mechanism of leukemogenesis by CBFß-SMMHC. Overall design: ChIC-seq, RNA-seq and scRNA-seq were used to study the DNA binding preference and gene expression changes caused by CBFß-SMMHC or RUNX1 variants or mutations during leukemogenesis.