Extensive editing of both processed and preprocessed maxicircle CR6 transcripts in Trypanosoma brucei

Area of Science:

• Molecular Biology
• Parasitology
• Genetics

Background:

• Trypanosoma brucei maxicircle genome transcripts undergo post-transcriptional RNA editing.
• RNA editing involves uridine insertion and deletion, altering transcript sequences.

Purpose of the Study:

• To investigate the RNA editing of CR6 gene transcripts in Trypanosoma brucei.
• To determine the impact of RNA editing on CR6 mRNA structure and protein coding potential.
• To explore the relationship between CR6 and downstream ND5 gene expression.

Main Methods:

• Analysis of CR6 and ND5 gene transcripts using cDNA sequencing.
• Quantification of unedited and edited CR6 transcripts in different parasite life stages.
• Bioinformatic analysis to identify open reading frames and protein homology.

Main Results:

• CR6 transcripts are heavily edited, with 132 uridine additions and 28 deletions, increasing mRNA size by 47%.
• RNA editing creates two novel open reading frames (ORFs) in CR6 mRNA, specifying small, hydrophobic proteins.
• Edited and unedited CR6 transcripts are more abundant in bloodstream form parasites.
• CR6 and ND5 transcripts originate from a common precursor, with a 37-nucleotide overlap.
• RNA editing can occur before precursor processing.

Conclusions:

• RNA editing significantly alters CR6 mRNA, generating new protein-coding potential.
• Polycistronic transcription of maxicircle genes is demonstrated for the first time.
• RNA editing and precursor processing are proposed regulatory mechanisms for maxicircle gene expression.