Determinants for cap trimethylation of the U2 small nuclear RNA are not conserved between Trypanosoma brucei and higher eukaryotic organisms

摘要: In most eukaryotic organisms the U2 small nuclear RNA (snRNA) gene is transcribed by polymerase II to generate a primary transcript with 5′ terminal 7-methylguanosine cap structure. Following export, snRNA assembled into core ribonucleoprotein particle (RNP). This involves binding set of proteins that are shared spliceosomal snRNPs highly conserved Sm site. Prior import, snRNA-(guanosine-N2)-methyltransferase appears interact RNP and hypermethylates structure 2,2,7-trimethylguanosine (m3G). protist parasite Trypanosoma brucei, U-snRNAs complexed common analogous antigens but do not have sequence motif, synthesised III. Here, we examined determinants for m3G formation in T.brucei expressing mutant snRNAs vivo assaying trimethylation assembly immunoprecipitation. Surprisingly, these studies revealed Sm-analogous region required either or trimethylation. Furthermore, except first 24 nt which part promoter, coding could be substituted deleted without affecting