EDITING OF TRYPANOSOMA-BRUCEI MAXICIRCLE CR5 MESSENGER-RNA GENERATES VARIABLE CARBOXY-TERMINAL PREDICTED PROTEIN SEQUENCES

RNA editing post-transcriptionally modifies several mRNAs from the max icircle of kinetoplastid parasites by addition and removal of uridine residues. We report here that maxicircle CR5 transcripts of Trypanosom a brucei are edited in two domains separated by an eight nucleotide se quence that remains unedited. The large 5' domain is edited to a conse nsus sequence while the smaller 3' domain is edited to multiple final sequences. In all, 205 - 217 Us are inserted and 13 - 16 encoded uridi nes are deleted from the CR5 mRNA, producing a mature transcript 75 - 80% larger than the unedited transcript. The edited RNAs predict small , highly hydrophobic proteins. The carboxy terminal 15 - 30% of these predicted proteins have multiple different amino acid sequences as a r esult of the variable edited 3' mRNA sequence, but these fall into two families of sequence. Limited amino acid sequence and hydrophobicity profile similarities suggest that the protein encoded by edited CR5 mR NA may be a subunit of NADH dehydrogenase.