SF3B1 mutations promote expression of a novel EVI1 isoform that enhances EVI1’s self-renewal capacity. (A) Schematic of EVI1 protein with 6 amino acid insertion (top) and representative RNA-seq coverage plot of SF3B1 WT and mutated inv(3) AML (bottom). (B) Fraction of the novel transcript (EVI1+18) compared with normal transcript in SF3B1 WT and SF3B1 mutated EVI1-rearranged AML. (C) RT-PCR illustrating the inclusion of intronic sequences in SF3B1 K700E-transduced MEL270 cells (top, red) and endogenously SF3B1 K700E harboring leukemia cells (bottom, red). (D) Sanger sequencing of complementary DNA (cDNA) arising from the top band in panel C. The nucleotide sequences and corresponding amino acids are indicated. (E) RT-PCR of human EVI1 and mouse Gapdh using cDNA derived from peripheral blood of 4 murine models. (F) Number of myeloid colonies on first to fourth plating of c-Kit⁺ BM cells transduced with empty vector (control), EVI1 (WT), or EVI1+18 cDNA (left). Representative images (right) of the sixth colony. (G) Genomic distribution of anti-EVI1 ChIP-seq peaks. (H) Coverage tracks showing EVI1 ChIP-seq occupancy at the indicated genomic loci. P values were calculated by 2-sided Student t test. *P < .05, **P < .01, ***P < .001, and ****P < .0001.