Poster abstracts
Poster number 86 submitted by Lauren Levesque
Role of nTr-25, a tRNA-Arg-UCU isodecoder, in establishment of left-right asymmetry in mammals
Lauren Levesque (Department of Molecular Genetics, The Ohio State University), Kara Braunreiter (Department of Molecular Genetics, The Ohio State University), Susan Cole (Department of Molecular Genetics)
Abstract:
Transfer RNA (tRNA) isodecoders are defined as tRNAs that have the same anticodon but differ in sequence within the rest of tRNA body. In both humans and mice, there are multiple isodecoders for 50 of 51 anticodons. Given these isodecoders are predicted to have the same function in translation, their genetic redundancy raises intriguing questions about their evolution and function. We are interested in the tRNAArgUCU isodecoder family as recent work has shown that a member of this family, nTr-20, shows neuron-specific expression and that a mutation in nTr-20 causes a neuronal phenotype in mice1. This data indicates isodecoders can have non-redundant functions in mammalian development. Another member in the tRNAArgUCU family is n-Tr25, encoded anti-sense to the 3’UTR of Hes7 which encodes a transcriptional repressor required for vertebrate segmentation.
Interestingly a case study identified a rare SNP allele (T>C) in the nTr-25 trailer that is homozygous in a proband with dextrocardia, a disorder in which the heart is on the right2. The rare ‘C’ allele disrupts a run of T’s two nucleotides downstream of the mature tRNA. We hypothesize that the rare SNP allele impairs RNAP III termination which negatively impacts tRNA maturation. This would cause a decrease in both the tRNAArgUCU pool and translation of proteins involved in establishing the left-right axis. Supporting this hypothesis, human mRNAs that have a high number of AGA codons (top 1%) are enriched in molecular functions known to affect establishment of left:right asymmetry3.
Our preliminary data supports the hypothesis that the ‘C’ allele alters tRNA processing. Our ongoing work will assess tRNAArgUCU expression during development and determine the phenotypes associated with loss of function mutations in mice. Additionally, we will use a combination of biochemical analyses and reporter assays to determine the effect of the rare allele on the biogenesis of translationally competent nTr-25.
References:
1. Lai, Lien B., et al. “Structural Basis for Impaired 5’ Processing of a Mutant tRNA Associated with Defects in Neuronal Homeostasis.” Proceedings of the National Academy of Sciences of the United States of America, vol. 119, no. 10, Mar. 2022, p. e2119529119. PubMed, https://doi.org/10.1073/pnas.2119529119.
2. Netravathi, Manjunath, et al. “Whole Exome Sequencing in an Indian Family Links Coats plus Syndrome and Dextrocardia with a Homozygous Novel CTC1 and a Rare HES7 Variation.” BMC Medical Genetics, vol. 16, Feb. 2015, p. 5. PubMed, https://doi.org/10.1186/s12881-015-0151-8.
3. Orellana, Esteban A., et al. “METTL1-Mediated m7G Modification of Arg-TCT tRNA Drives Oncogenic Transformation.” Molecular Cell, vol. 81, no. 16, Aug. 2021, pp. 3323-3338.e14. ScienceDirect, https://doi.org/10.1016/j.molcel.2021.06.031.
Keywords: tRNA maturation, Development, Isodecoder