NUCLEAR FATE OF YEAST SNORNA IS DETERMINED BY COTRANSCRIPTIONAL RNT1 CLEAVAGE

We show that in S. cerevisiae pre-snoRNA processing by the endonuclease Rnt1 occurs co-transcriptionally, removing the m7G cap to facilitate the formation of box C/D snoRNA. Failure to remove m7G cap from box C/D pre-snoRNA affects 3’ end processing, ribonucleoprotein complex formation and causes mislocalization to the cytoplasm. Consequently, Rnt1-dependent 5’ end processing of box C/D snoRNA is critical for snoRNA-dependent methylation of ribosomal RNA. Our results reveal that the 5’ end processing defines a distinct pathway for snoRNA maturation.