Characterization of the Trypanosoma brucei cap hypermethylase Tgs1

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• 作者：Jia-peng Ruan ; Elisabetta Ullu ; Christian Tschudi
• 关键词：TMG cap ; U2 snRNA ; U3 snoRNA ; RNAi ; Nop10
• 刊名：Molecular and Biochemical Parasitology
• 出版年：2007
• 期刊代码：108_01666851
• 类别：bio
• 出版时间：September 2007
• 卷：155
• 期：1
• 页码：66-69
• 文件大小：715 K

摘要

Many U-snRNAs contain a hypermodified 2,2,7-trimethylguanosine (TMG) cap structure, which is formed by post-transcriptional methylation of an m⁷G cap. At present, little is known about the maturation of U-snRNAs in trypanosomes. The current evidence is consistent with the primary transcript containing an m⁷G moiety, but it is not clear whether the conversion of m⁷G to TMG takes place in the cytoplasm or in the nucleus. To address this issue, we characterized the Trypanosoma brucei homologue of the trimethylguanosine synthase (TbTgs1), a 28 kDa protein, which is mainly composed of the conserved catalytic domain and lacks a large N-terminal domain present in higher eukaryotes. A GFP fusion with TbTgs1 revealed that this protein localizes throughout the nucleoplasm, as well as in one or two dots outside the nucleolus and RNAi-mediated downregulation of TbTgs1 suggests that this protein is responsible for hypermethylation of the m⁷G cap of both snRNAs and snoRNAs.