The splicing factor RBM25 controls MYC activity in Acute Myeloid Leukemia

Cancer sequencing studies have implicated regulators of pre-mRNA splicing as important disease determinants in Acute Myeloid Leukemia (AML), but the underlying mechanisms have remained elusive. We hypothesized that “non-mutated” splicing regulators may also play a role in AML biology and therefore conducted an in vivo shRNA screen in a mouse model of CEBPA mutant AML. This led to the identification of the splicing regulator RBM25 as a novel tumor suppressor, and down-regulation of RBM25 increased proliferation and decreased apoptosis in human leukemic cell lines. Mechanistically, we could show that RBM25 controlled the splicing of key genes, including those encoding the apoptotic regulator BCL-x and the MYC inhibitor BIN1. Specifically, we demonstrated that RBM25 acts as a regulator of MYC activity and sensitizes cells to increased MYC levels. This mechanism also appears to be operative in human AML patients where RBM25 levels correlative inversely with MYC activity and clinical outcome. Examined transcriptome from U937 cells in biological triplicates.