Notably, KD of U2AF1 had this effect in both K562 and HepG2 cells (Fig 6A), and mutations in U2AF1 in myelodysplastic syndromes are associated with reduction of Pol2 pause release and R loop accumulation (Chen et al, 2018; Nguyen et al, 2018). Here, U2AF1 is linked to myelodysplastic syndrome.