TRYPANOSOMA-BRUCEI MITOCHONDRIAL CR4 GENE ENCODES AN EXTENSIVELY EDITED MESSENGER-RNA WITH COMPLETELY EDITED SEQUENCE ONLY IN BLOOD-STREAM FORMS

Several kinetoplastid mitochondrial genes cannot be expressed without RNA editing of their transcripts to create a functional open reading f rame. We have examined one such mitochondrial gene, CR4, in Trypanosom a brucei EATRO164 and find extensive editing of transcripts in both bl oodstream and procyclic life cycle stages. However, a consensus edited sequence for the entire mRNA occurs only in the bloodstream stage. Th e unedited CR4 transcript is 283 nucleotides in length, not including the poly(A) tail. A total of 325 uridines are inserted, and 40 uridine s deleted, to create the mature mRNA which encodes a very hydrophobic protein.