Mediates the splicing of pre-mRNA by binding to the stem loop I region of U1-snRNA (PubMed:15611175). Required during oogenesis for nurse cell chromatin dispersal (PubMed:24244416). Component of the U1 snRNP (By similarity). Interacts with Psi; essential for alternative splicing of P-element transposase. Interacts with the SMN complex. Expressed both maternally and zygotically throughout all development. Protein interactions mediated by the Arg-rich domain are not essential for viability, but do contribute to an essential U1 snRNP function. The RRM domain mediates interaction with U1 RNA. Lethal during embryogenesis (PubMed:15611175). RNAi-mediated knockdown in the germline results in defective nurse cell nuclei decondensation and dispersal ultimately affecting oogenesis (PubMed:24244416).