Poster abstracts
Poster number 83 submitted by Raphael Lopes
Unravelling the Trl1–like enzyme function in Trypanosoma brucei
Raphael R. S. Lopes (Instituto de Bioquimica Medica, Universidade Federal do Rio de Janeiro), Gilbert S. Oliveira, Roberta Eitler (Instituto de Bioquimica Medica, Universidade Federal do Rio de Janeiro), Zdenek Paris (Microbiology Department, The Ohio State University), Juan D. Alfonzo (Microbiology Department; The Ohio State University), Raphael S. Vidal (Instituto de Bioquimica Medica, Universidade Federal do Rio de Janeiro), Carla Polycarpo (Instituto de Bioquimica Medica, Universidade Federal do Rio de Janeiro)
Abstract:
Transfer RNAs (tRNAs) play a central role in protein synthesis as translators of the genetic code connecting the information found in genes to that ultimately deposited into proteins. The biosynthesis of mature and functional tRNAs involves many processing steps, including 5’ and 3’ end trimming, incorporation of numerous chemical post-transcriptional modifications and addition of a CCA sequence at the 3’ end. A subset of tRNAs, that varies with different organisms, also contain introns that are cleaved by a tRNA splicing endonuclease, generating exon halves that are subsequently sealed by a splicing-specific tRNA ligase. We have identified a homolog of yeast tRNA ligase (Trl1) in trypanosomatids, that is presumably responsible for the joining of the two tRNA exon halves generated by endonuclease cleavage of tRNATyr; the only intron-containing tRNA in these organisms. In the present work, we have preliminarily characterized the Trl-1 homolog of T. brucei (TbTrl1). We constructed a stable T. brucei RNAi knockdown strain of Tbtrl1 and show that RNAi induction leads to a severe growth defect. Unexpectedly, RNAi of TbTrl1 caused accumulation of intron-containing tRNA, as opposed to unligated exon halves, and almost a complete disappearance of mature tRNA. Furthermore, down-regulation of TbTrl1 also led to pronounced cell-cycle arrest. Taken together these results demonstrate the essentiality of the TbTrl1 homolog for cell viability. The observed accumulation of intron-containing tRNA is discussed in the context of the intra-cellular localization of TbTrl1 and its potential role in tRNA export from the nucleus. The restricted phylogenetic distribution to fungi and trypanosomatids for Trl1-splicing ligases shown in this work makes this family of enzymes promising therapeutic targets for such medically important organisms.
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Acknowledgements: This research was supported by NIH,FAPERJ and CNPq
Keywords: tRNA ligase, Trypanosoma, Editing