Involved in pre-mRNA splicing as a component of the spliceosome (PubMed:28781166). Regulates alternative splicing of the HSPG2 pre-mRNA (By similarity). Required for normal accumulation of IK (PubMed:24945353). Required for normal mitotic spindle assembly and normal progress through mitosis (By similarity). (Microbial infection) Required, together with IK, for normal splicing of influenza A virus NS1 pre-mRNA, which is required for the production of the exportin NS2 and for the production of influenza A virus particles. Not required for the production of VSV virus particles. Component of the spliceosome B complex (PubMed:22365833, PubMed:28781166). Interacts with IK (PubMed:28781166, PubMed:24945353, PubMed:22365833). (Microbial infection) Identified in a complex with IK and influenza A virus RNA polymerase subunits PB1 and PB2; does not directly interact with the viral proteins by itself. Colocalizes with SRSF1 in nuclear speckles. The WD repeats assemble into a seven-bladed WD propeller. Belongs to the WD repeat SMU1 family.