Abstract
We have found two enzymatic activites in whole cell extracts from Trypanosoma brucei; an end-labeling reaction involving a single uridine at the 3′ end of ribosomal RNAs (rRNAs) and an RNA ligase activity Joining 5′ monophosphates to 3′ hydroxyl groups. The RNA ligase acts upon one of the small rRNAs (180 nucleotides) from the trypanosome ribosomal repeat unit, forming a circular RNA. The specific circularization of this small rRNA is probably dependent on the secondary structure of the molecule and is not detectable in vivo.