Constructive edge of uridylation-induced RNA degradation.
RNA Biol
; 13(11): 1078-1083, 2016 Nov.
Article
en En
| MEDLINE
| ID: mdl-27715485
ABSTRACT
RNA uridylation is a significant transcriptome-shaping factor in protists, fungi, metazoans, and plants. The 3' U-additions are catalyzed by terminal uridyltransferases (TUTases), a diverse group of enzymes that along with non-canonical poly(A) polymerases form a distinct group in the superfamily of DNA polymerase ß-like nucleotidyl transferases. Within and across studied organisms and subcellular compartments, TUTases differ in nucleotide triphosphate selectivity, interacting partners, and RNA targets. A general premise linking RNA uridylation to 3'-5' degradation received support from several studies of small RNAs and mRNA turnover. However, recent work on kinetoplastid protists typified by Trypanosoma brucei provides evidence that RNA uridylation may play a more nuanced role in generating functional small RNAs. In this pathogen's mitochondrion, most mRNAs are internally edited by U-insertions and deletions, and subjected to 3' adenylation/uridylation; guide RNAs (gRNAs) required for editing are U-tailed. The prominent role of uridylation in mitochondrial RNA metabolism stimulated identification of the first TUTase, RNA editing TUTase 1 (RET1). Here we discuss functional studies of mitochondrial uridylation in trypanosomes that have revealed an unorthodox pathway of small RNA biogenesis. The current model accentuates physical coupling of RET1 and 3'-5' RNase II/RNB-type exonuclease DSS1 within a stable complex termed the mitochondrial 3' processome (MPsome). In the confines of this complex, RET1 initially uridylates a long precursor to activate its 3'-5' degradation by DSS1, and then uridylates trimmed guide RNA to disengage the processing complex from the mature molecule. We also discuss a potential role of antisense transcription in the MPsome pausing at a fixed distance from gRNA's 5' end. This step likely defines the mature 3' end by enabling kinetic competition between TUTase and exonuclease activities.
Palabras clave
Texto completo:
1
Colección:
01-internacional
Banco de datos:
MEDLINE
Asunto principal:
Trypanosoma
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Uridina
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ARN Mensajero
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ARN Pequeño no Traducido
Tipo de estudio:
Prognostic_studies
Idioma:
En
Revista:
RNA Biol
Asunto de la revista:
BIOLOGIA MOLECULAR
Año:
2016
Tipo del documento:
Article
País de afiliación:
Estados Unidos