RNA-binding protein that acts as a regulator of alternative pre-mRNA splicing. Involved in apoptotic cell death through the regulation of the apoptotic factor BCL2L1 isoform expression. Modulates the ratio of proapoptotic BCL2L1 isoform S to antiapoptotic BCL2L1 isoform L mRNA expression. When overexpressed, stimulates proapoptotic BCL2L1 isoform S 5'-splice site (5'-ss) selection, whereas its depletion caused the accumulation of antiapoptotic BCL2L1 isoform L. Promotes BCL2L1 isoform S 5'-ss usage through the 5'-CGGGCA-3' RNA sequence. Its association with LUC7L3 promotes U1 snRNP binding to a weak 5' ss in a 5'-CGGGCA-3'-dependent manner. Binds to the exonic splicing enhancer 5'-CGGGCA-3' RNA sequence located within exon 2 of the BCL2L1 pre-mRNA (By similarity). Interacts with LUC7L3 and SRRM1 (By similarity). Specifically associates with functional splicing complexes, including Sm proteins and U1, U2, U4, U5 and U6 snRNAs (By similarity). Associates with exon junction complex (EJC) proteins, including APEX1, DDX39B, NCBP1, RBM8A and RNPS1. Interaction with NCBP1 is RNA-dependent (By similarity). Colocalizes predominantly, with SFRS2 and LUC7L3 splicing factors, in nuclear speckles. Cytoplasmic localization is faint (By similarity). The PWI domain binds nucleic acids with significant help from its N-terminal flanking basic region. It has an equal preference for binding to single- or double-stranded species, and it contributes to RBM25 role in modulation of alternative splicing, maybe by mediating RNA-dependent association with LUC7L3 (By similarity). Sumoylated. Truncated N-terminus. Probable cloning artifact. Truncated N-terminus. Truncated N-terminus. Aberrant splicing. Truncated N-terminus. Truncated N-terminus.