Characterization of small nucleolar RNAs in the protist organism Euglena gracilis

Non-coding RNAs (ncRNAs) have diverse cellular roles in all three domains of life. One class of ncRNAs termed small nucleolar RNAs (snoRNAs) play a role in RNA modification and processing in archaea and eukaryotic organisms. ncRNAs (including snoRNAs) remain largely unexplored in a group of unicellular eukaryotes known as protists. The focus of this study was to characterize snoRNAs in the protist organism Euglena gracilis in terms of their genomic arrangement, expression and evolution using experimental and computational methods. Numerous novel snoRNAs were characterized, many of which reside in tandemly repeated clusters that can be transcribed polycistronically. Some snoRNA gene clusters are surprisingly large, possibly the largest characterized to date. A mechanism of snoRNA evolution to support the unusually large number of snoRNAs and clustered modification sites in E. gracilis was characterized. These findings exemplify snoRNA diversity and highlight the importance of ncRNA characterization in a broad range of organisms.