. "Component of the U4/U5/U6 snRNP, binding principally to the u5 snRNP. It is not absolutely required for the second step of pre-mRNA splicing at low temperatures but is required at higher temperatures. It may stabilize a particular conformation of the U5 snRNP or orient the U5 snRNP within the U4/U5/U6 snRNP or within the spliceosome." .