The human U4/U6 snRNP contains 60 and 90kD proteins that are structurally homologous to the yeast splicing factors Prp4p and Prp3p.
J Lauber, G Plessel, S Prehn, C L Will, P Fabrizio, K Gröning, W S Lane, and R Lührmann
RNA. 1997 August; 3(8): 926–941. PMCID: PMC1369537