Multiple guide RNAs for identical editing of Trypanosoma brucei apocytochrome b mRNA have an unusual minicircle location and are developmentally regulated.

We identified four different guide RNAs (gRNAs) that specify identical editing of Trypanosoma brucei apocytochrome b (CYb) mRNA, which indicates gRNA redundancy in T. brucei. All four gRNAs appear functional since they occur in chimeras, some of which contain an interesting gRNA 3' "extension." The gRNAs are encoded in different minicircles, rather than maxicircles as in other species. However, these gRNA genes are not between 18-base pair repeats as are the other minicircle gRNA genes in T. brucei. The three minicircles cloned contain the same gRNA genes, one of which is substantially diverged, all in the same order, indicating that they are related. CYb gRNA is less abundant in procyclic than bloodstream forms. Procyclic forms contain abundant edited CYb mRNA unlike bloodstream forms thus suggesting that CYb mRNA editing may be regulated at the level of gRNA utilization.