Poster abstracts
Poster number 81 submitted by Jeremy Lant
Natural tRNA variation and visualizing mistranslation in human cells.
Jeremy T. Lant (Dept. of Biochemistry, Western University), Matthew D. Berg (Dept. of Biochemistry, Western University), Christopher J. Brandl (Dept. of Biochemistry, Western University), Patrick ODonoghue (Dept. of Biochemistry, Western University)
Abstract:
The human cytosolic tRNA pool is astoundingly complex. Over 600 tRNA or tRNA-like genes encode over 400 expressed tRNAs(1). Each tRNA contains an average of 13 post-transcriptional modifications, amounting to over 213 microspecies that must coordinate to faithfully decode only 61 sense codons(2). Despite this complexity, we demonstrated with a fluorescent reporter that a single tRNA variant expressed in HEK293 cells could elicit up to 2-5% mistranslation of a proline codon (Pro to Ala)(3). Interestingly, we could only observe significant levels of mistranslation after cells were deprived of serum and glucose for four days(3). Also, cells were surprisingly mistranslation-tolerant, as no induction of the heat shock response, or loss in cellular viability could be detected(3). Our findings point to a ‘hidden phenotypes’ model of cytosolic tRNA behavior, where mistranslating tRNAs can exist quietly until a combinatorial factor exacerbates their phenotype. Indeed, tRNA expression profiles vary between tissues, can respond to stimuli, and become altered in many diseases including cancer(4). More recently, we have completed high-coverage sequencing of all tRNA genes in a cohort of 48 healthy individuals to better understand the prevalence of natural tRNA variants in the human population. We have also been composing a review paper on the behaviors of cytosolic tRNAs in human disease. I discuss our early work on tRNA-dependent mistranslation in cell culture, and new perspectives on the roles of cytosolic tRNA variants in human disease.
References:
1.Chan, P. P. & Lowe, T. M. GtRNAdb 2.0: an expanded database of transfer RNA genes identified in complete and draft genomes. Nucleic Acids Res. 44, D184–D189 (2016).
2.Schimmel, P. The emerging complexity of the tRNA world: mammalian tRNAs beyond protein synthesis. Nat. Rev. Mol. Cell Biol. 19, 45–58 (2017).
3.Lant, J. T. et al. Visualizing tRNA-dependent mistranslation in human cells. RNA Biol. (2017).
4.Kirchner, S. & Ignatova, Z. Emerging roles of tRNA in adaptive translation, signalling dynamics and disease. Nat. Rev. Genet. 16, 98–112 (2015).
Keywords: Transfer RNA, mistranslation, human disease