sentences:  Yeast U1 spliceosomal RNA
  
  U1 is a small nuclear RNA (snRNA) component of the spliceosome and is involved in pre-mRNA splicing.In the splicing process the 5' end of the U1 snRNA forms complementary base pairing with the 5' splice junction of the inton to be excised, thus defining the 5' donor site of an intron.