The human Imp3 and Imp4 proteins form a ternary complex with hMpp10, which only interacts with the U3 snoRNA in 60-80S ribonucleoprotein complexes.
Granneman S, Gallagher JE, Vogelzangs J, Horstman W, van Venrooij WJ, Baserga SJ, Pruijn GJ. Nucleic Acids Res. 2003 Apr 1; 31(7):1877-87.