COMPLEXES FROM TRYPANOSOMA-BRUCEI THAT EXHIBIT DELETION EDITING AND OTHER EDITING-ASSOCIATED PROPERTIES

Transcripts from many mitochondrial genes in kinetoplastids undergo RN A editing, a posttranscriptional process which inserts and deletes uri dines, By assaying for deletion editing in vitro, we found that the ed iting activity from Trypanosoma brucei mitochondrial lysates (S. D. Se iwert and K. D. Stuart, Science 266:114-117, 1994) sediments with a pe ak of similar to 20S. RNA helicase, terminal uridylyl transferase, RNA ligase, and adenylation activities, which may have a role in editing, cosediment in a broad distribution, with most of each activity at 35 to 40S. Most ATPase 6 (A6) guide RNA and unedited A6 mRNA sediments at 20 to 30S, with some sedimenting further into the gradient, while mos t edited A6 mRNA sediments at >35S. Several mitochondrial proteins whi ch cross-link specifically with guide RNA upon UV treatment also sedim ent in glycerol gradients, Notably, a 65-kDa protein sediments primari ly at similar to 20S, a 90-kDa protein sediments at 35 to 40S, and a 2 5-kDa protein is present at <10S, Most ribonucleoprotein complexes tha t form,vith gRNA in vitro sediment at 10 to 20S, except for one, which sediments at 30 to 45S. These results suggest that RNA editing takes place within a multicomponent complex, The potential functions of and relationships between the 20S and 35 to 40S complexes are discussed.