TbMP42, a protein component of the RNA editing complex in African trypanosomes, has endo-exoribonuclease activity.
RNA editing in trypanosomatids is catalyzed by a high molecular mass RNP complex, which is only partially characterized. TbMP42 is a 42 kDa protein of unknown function that copurifies with the editing complex. The polypeptide is characterized by two Zn fingers and a potential barrel structure/OB-fold at its C terminus. Using recombinant TbMP42, we show that the protein can bind to dsRNA and dsDNA but fails to recognize DNA/RNA hybrids. rTbMP42 degrades ssRNA by a 3' to 5' exoribonuclease activity. In addition, rTbMP42 has endoribonuclease activity, which preferentially hydrolyzes non-base-paired uridylate-containing sequences. Gene silencing of TbMP42 inhibits cell growth and is ultimately lethal to the parasite. Mitochondrial extracts from TbMP42-minus trypanosomes have only residual RNA editing activity and strongly reduced endo-exoribonuclease activity. However, all three activities can be restored by the addition of rTbMP42. Together, the data suggest that TbMP42 contributes both endo- and exoribonuclease activity to the editing reaction cycle.
Brecht
Michael
M
Department of Microbiology and Genetics, Darmstadt University of Technology, Schnittspahnstrasse 10, 64287 Darmstadt, Germany.
Niemann
Moritz
M
Schlüter
Elke
E
Müller
Ulrich F
UF
Stuart
Ken
K
Göringer
H Ulrich
HU
D000818:Animals; D015374:Biosensing Techniques; D002412:Cations; D002942:Circular Dichroism; D003001:Cloning, Molecular; D004247:DNA / Q000737:chemistry; D018076:DNA, Complementary / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004591:Electrophoresis, Polyacrylamide Gel; D020868:Gene Silencing; D006801:Humans; D006868:Hydrolysis; D008928:Mitochondria / Q000378:metabolism; D010455:Peptides / Q000737:chemistry; D010641:Phenotype; D017510:Protein Folding; D017434:Protein Structure, Tertiary; D015800:Protozoan Proteins / Q000737:chemistry / Q000502:physiology*; D012313:RNA / Q000737:chemistry; D017393:RNA Editing; D034622:RNA Interference; D012330:RNA, Double-Stranded / Q000737:chemistry; D012333:RNA, Messenger / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry; D012260:Ribonucleases / Q000378:metabolism; D012261:Ribonucleoproteins / Q000737:chemistry / Q000502:physiology*; D014346:Trypanosoma brucei brucei; D015032:Zinc / Q000737:chemistry; D016335:Zinc Fingers
D002412:Cations; D018076:DNA, Complementary; D010455:Peptides; D015800:Protozoan Proteins; D012330:RNA, Double-Stranded; D012333:RNA, Messenger; D011994:Recombinant Proteins; D012261:Ribonucleoproteins; C437999:TbMP42 protein, Trypanosoma brucei; D012313:RNA; D004247:DNA; D012260:Ribonucleases; D015032:Zinc