To study the impact of SF3B1 mutations on alternative splicing and the effect of H3B-8800 splicing modulator in wild type and SF3B1-mutant chronic lymphocytic leukemia cells, we established SF3B1 K700E MEC1 CLL isogenic cell line and carried out RNA deep sequencing in SF3B1 wild type and K700E MEC1 cell lines upon H3B-8800 treatment. Overall design: MEC1 SF3B1 wild type and SF3B1 K700E chronic lymphocytic leukemia cell lines treated for 6 hours with H3B-8800 75nM.