Fig 2: SF3B6 is required in DKFZp434J0226 (DKFZ)-induced proliferation and migration. A–C Cell growth curves assay (A), soft agar colony formation assay (B), and western blotting of PCNA (C) demonstrating that SF3B6 knockdown rescues DKFZ-induced cell proliferation. D Migration assay demonstrating that SF3B6 knockdown rescues DKFZ-induced cell migration. E RT-qPCR demonstrating that SF3B6 knockdown rescues DKFZ-induced alternative splicing of MDM-4. A Data are shown as mean ± SD; *P < 0.05 vs. Mock and N; **P < 0.01 vs. DKFZ. B–E Data are shown as mean ± SD; *P < 0.05, **P < 0.01. Scale bars refer to 100 µm

Fig 3: DKFZp434J0226 (DKFZ) inhibits xenograft tumor growth. MiaPaCa-2 cells infected with control lentivirus (control, n = 6) and DKFZ lentivirus (DKFZ, n = 7) were injected subcutaneously into nude mice. A Tumor size. B In vivo subcutaneous tumor growth curves. Data are shown as mean ± SD; *P < 0.05 vs. Mock and NC; **P < 0.01 vs. control. C Total tumor weight of each group of mice. D Western blotting analysis and quantification of SF3B6 phosphorylation levels in indicated tumors (n = 4). E The alternative spliced transcripts (MDM4-FL, MDM4 full-length transcript; MDM4-S, MDM4 S transcript) in the indicated tumors verified by RT-qPCR. The percent spliced in index was quantified for the alternative splicing events (n = 4). C–E Data are shown as mean ± SD; *P < 0.05, **P < 0.01

Fig 4: SF3B6 serves as a DKFZp434J0226 (DKFZ)-binding protein. A RNA pull-down assay performed in the HEK293T cell lysates with biotin-labeled oligos. After pull-down, proteins were subjected to SDS-PAGE and stained by Coomassie brilliant blue. The band indicated by the arrow was subjected to mass spectrometry. B Western blotting analysis determined the specific interaction of sense DKFZ with SF3B6 protein, but not with PCNA protein (negative control). C RNA immunoprecipitation (RIP) of SF3B6 interaction with DKFZ in the HEK293T cells. RNA-protein complexes immunoprecipitated by anti-SF3B6 or control IgG were determined by RT-qPCR using specific primers for DKFZ or MEG3 (negative control). Data are shown as mean ± SD (n = 4); **P < 0.01. D Western blotting analysis of SF3B6 levels in the indicated DKFZ overexpression AsPC-1 cells or DKFZ knockdown MIAPaCa-2 cells. E Western blotting analysis of SF3B6 phosphorylation levels in the indicated DKFZ overexpression AsPC-1 cells or DKFZ knockdown MIAPaCa-2 cells. For SF3B6 phosphorylation detection, cell lysates were prepared and subjected to immunoprecipitation (IP) with anti-SF3B6 antibody, followed by immunoblotting analysis with the anti-phospho-tyrosine antibody