removal of the 5 ' terminal sequences of u1 rna by oligo-directed cleavage or removal of u1 snrnps by immunoprecipitation prior to the addition of precursor rna depressed the association of all snrnps with precursor rna as detected by immunoprecipitation of splicing complexes by either sm or u1-specific antibodies .
C0162795
u1 snrnps
C0142661
snrnps