The messenger RNA decapping and recapping pathway in Trypanosoma.
Proc Natl Acad Sci U S A
; 112(22): 6967-72, 2015 Jun 02.
Article
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| MEDLINE
| ID: mdl-26038549
ABSTRACT
The 5' terminus of trypanosome mRNA is protected by a hypermethylated cap 4 derived from spliced leader (SL) RNA. Trypanosoma brucei nuclear capping enzyme with cap guanylyltransferase and methyltransferase activities (TbCgm1) modifies the 5'-diphosphate RNA (ppRNA) end to generate an m7G SL RNA cap. Here we show that T. brucei cytoplasmic capping enzyme (TbCe1) is a bifunctional 5'-RNA kinase and guanylyltransferase that transfers a γ-phosphate from ATP to pRNA to form ppRNA, which is then capped by transfer of GMP from GTP to the RNA ß-phosphate. A Walker A-box motif in the N-terminal domain is essential for the RNA kinase activity and is targeted preferentially to a SL RNA sequence with a 5'-terminal methylated nucleoside. Silencing of TbCe1 leads to accumulation of uncapped mRNAs, consistent with selective capping of mRNA that has undergone trans-splicing and decapping. We identify T. brucei mRNA decapping enzyme (TbDcp2) that cleaves m7GDP from capped RNA to generate pRNA, a substrate for TbCe1. TbDcp2 can also remove GDP from unmethylated capped RNA but is less active at a mature cap 4 end and thus may function in RNA cap quality surveillance. Our results establish the enzymology and relevant protein catalysts of a cytoplasmic recapping pathway that has broad implications for the functional reactivation of processed mRNA ends.
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Texto completo:
1
Colección:
01-internacional
Banco de datos:
MEDLINE
Asunto principal:
Trypanosoma brucei brucei
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Caperuzas de ARN
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ARN Mensajero
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Proteínas Protozoarias
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Metilación de ADN
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Endorribonucleasas
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Nucleotidiltransferasas
Idioma:
En
Revista:
Proc Natl Acad Sci U S A
Año:
2015
Tipo del documento:
Article