A new snRNA with a trimethylated cap structure in the slime mold Physarum polycephalum

Small nuclear RNAs with a trimethylated guanine in their cap structure were isolated from P. polycephalum nuclei using antibodies specific for m3G, as previously described. In addition to U1, U2, U4 and U5 snRNAs a new snRNA species was recovered. Two molecules belonging to this new RNA species were reproducibly obtained. They only differed by a 3'-end heterogeneity, one additional U residue in the longest molecule, which is 128 nucleotides in length. We denoted this new snRNA: PhyUR.