DEVELOPMENTAL REGULATION OF RNA EDITING AND POLYADENYLATION IN 4 LIFE-CYCLE STAGES OF TRYPANOSOMA-CONGOLENSE

The accumulation of many edited mRNAs is developmentally regulated in a transcript-specific fashion in Trypanosoma brucei. In addition, thes e transcripts are frequently present in two size classes which differ substantially in the lengths of their poly(A) tails, and poly(A) tail length is also developmentally regulated. Previously, these phenomena have only been studied in the mammalian bloodstream and insect procycl ic forms (BF and PF, respectively) of T. brucei. In this paper, we exa mine developmental regulation of edited RNA abundance and poly(A) tail length of 3 mitochondrially encoded RNAs in mammalian BF and 3 insect stages (PF, epimastigotes, and metacyclics) of T. congolense. T. cong olense BF and PF are similar, but not identical, to these stages of T. brucei with regard to edited RNA accumulation and poly(A) tail length . At the level of edited RNA, both epimastigotes and metacyclic stage parasites appear to be pre-adapted for the respiratory mechanisms of B F but not yet down-regulated from the cytochrome-based respiration of PF since edited RNAs encoding NADH dehydrogenase components are up-reg ulated and edited CYb RNA is abundant in these stages. Poly(A) tail le ngths of mitochondrial mRNAs appear to be regulated independently of e dited RNA abundance. These results indicate that multiple mechanisms f or regulation of mitochondrial gene expression are active throughout t he trypanosome life cycle.