期刊
MOLECULAR AND BIOCHEMICAL PARASITOLOGY
卷 156, 期 2, 页码 246-254出版社
ELSEVIER
DOI: 10.1016/j.molbiopara.2007.09.001
关键词
mRNA capping; guanylyltransferase; cap 4 modification; Trans-splicing; SL RNA; RNAi
资金
- NIAID NIH HHS [AI43594, R01 AI043594, R01 AI043594-09] Funding Source: Medline
Capping of the pre-mRNA 5'end by addition a monomethylated guanosine cap (m(7)G) is an essential and the earliest modification in the biogenesis of mRNA. The reaction is catalyzed by three enzymes: triphosphatase, guanylyltransferase, and (guanine N-7) methyltransferase. Whereas this modification occurs co-transcriptionally in most eukaryotic organisms, trypanosomatid protozoa mRNAs acquire the m7G cap by trans-splicing, which entails the transfer of the capped spliced leader (SL) from the SL RNA to the mRNA. Intriguingly, the genomes of all trypanosomatid protozoa sequenced to date possess two distinct proteins with the signature motifs of guanylyltransferases:TbCGM1 and the previously characterized TbCE1. Here we provide biochemical evidence that TbCgm1 is a capping enzyme. Whereas RNAi-induced downregulation of TbCe1 had no phenotypic consequences, we found that TbCGM1 is essential for trypanosome viability and is required for SL RNA capping. Furthermore, consistent with co-transcriptional addition of the m(7)G cap, chromatin immunoprecipitation revealed recruitment of TbCgm1 to the SL RNA genes. (c) 2007 Elsevier B.V. All rights reserved.
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