Small nucleolar RNAs controlling rRNA processing in Trypanosoma brucei

Area of Science:

• Molecular Biology
• Parasitology
• Genetics

Background:

• Trypanosomes exhibit a unique ribosomal RNA (rRNA) processing pathway, differing significantly from other eukaryotes.
• The large subunit (LSU) rRNA is fragmented into multiple smaller pieces (srRNAs), necessitating specialized factors for maturation.

Purpose of the Study:

• To investigate the function of 10 abundant small nucleolar RNAs (snoRNAs) in trypanosome LSU rRNA processing.
• To elucidate the roles of snoRNAs in guiding rRNA modifications and precursor interactions during maturation.

Main Methods:

• Systematic examination of 10 abundant snoRNAs involved in rRNA processing.
• SnoRNA silencing experiments to assess functional impact.
• Analysis of snoRNA interactions with rRNA precursors and modifications.

Main Results:

• Each studied snoRNA associates with either early or late LSU rRNA biogenesis steps.
• Five snoRNAs interact with intervening sequences, while others guide rRNA modifications.
• LSU rRNA processing order deviates from transcription; srRNAs 2, 4, and 6 are processed before srRNA1.
• Six snoRNAs affecting srRNA1 processing guide modifications near the protein exit tunnel, potentially acting as checkpoints.

Conclusions:

• This study identifies a significant number of snoRNAs involved in trypanosome rRNA processing and folding.
• The findings highlight the critical role of snoRNAs in the unique maturation events of trypanosome rRNA.
• RRNA modifications guided by snoRNAs may act as crucial checkpoints in the complex trypanosome rRNA maturation pathway.