Compositionally and functionally distinct editosomes in Trypanosoma brucei.
Uridylate insertion/deletion RNA editing in Trypanosoma brucei mitochondria is catalyzed by a multiprotein complex, the approximately 20S editosome. Editosomes purified via three related tagged RNase III proteins, KREN1 (KREPB1/TbMP90), KREPB2 (TbMP67), and KREN2 (KREPB3/TbMP61), had very similar but nonidentical protein compositions, and only the tagged member of these three RNase III proteins was identified in each respective complex. Three new editosome proteins were also identified in these complexes. Each tagged complex catalyzed both precleaved insertion and deletion editing in vitro. However, KREN1 complexes cleaved deletion but not insertion editing sites in vitro, and, conversely, KREN2 complexes cleaved insertion but not deletion editing sites. These specific nuclease activities were abolished by mutations in the putative RNase III catalytic domain of the respective proteins. Thus editosomes appear to be heterogeneous in composition with KREN1 complexes catalyzing cleavage of deletion sites and KREN2 complexes cleaving insertion sites while both can catalyze the U addition, U removal, and ligation steps of editing.
Panigrahi
Aswini K
AK
Seattle Biomedical Research Institute, WA 98109, USA.
Ernst
Nancy Lewis
NL
Domingo
Gonzalo J
GJ
Fleck
Michele
M
Salavati
Reza
R
Stuart
Kenneth D
KD
D000595:Amino Acid Sequence; D000818:Animals; D002384:Catalysis; D004720:Endonucleases / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D017354:Point Mutation; D015800:Protozoan Proteins / Q000235:genetics / Q000378:metabolism; D017393:RNA Editing / Q000502:physiology; D043244:Ribonuclease III / Q000235:genetics / Q000378:metabolism*; D016415:Sequence Alignment; D014346:Trypanosoma brucei brucei / Q000201:enzymology / Q000235:genetics*
D015800:Protozoan Proteins; D004720:Endonucleases; D043244:Ribonuclease III