Involved in the first step of pre-mRNA splicing. Required for cell growth and cell cycle control. Plays a role in the levels of the U1, U4, U5 and U6 snRNAs and the maintenance of the U4/U6 snRNA complex. May provide the link between the 'nineteen complex' NTC spliceosome protein complex and the spliceosome through the U6 snRNA. Associates predominantly with U6 snRNAs in assembled active spliceosomes. Binds directly to the internal stem-loop (ISL) domain of the U6 snRNA and to the pre-mRNA intron near the 5' splice site during the activation and catalytic phases of the spliceosome cycle (By similarity). Associated with the spliceosome. The C-terminal RRM domain and the zinc finger motif are necessary for RNA-binding. Belongs to the RRM CWC2 family.