Component of the spliceosome and rRNA processing machinery. In association with the spliceosomal U4/U6.U5 tri-snRNP particle, required for splicing of pre-mRNA (By similarity). Component of the 25S U4/U6.U5 tri-snRNP particle, a subcomplex of the spliceosome. Interacts with PRP38 (By similarity). Belongs to the SPP381 family.