Poster abstracts
Poster number 19 submitted by Katie Clark
tRNA family-specific turnover pathways and environmental stresses regulate tRNA intron degradation
Katherine Clark (Department of Molecular Genetics, Center for RNA Biology, OSU, Columbus, OH), Sara Metcalf (Department of Molecular Genetics, Center for RNA Biology, OSU, Columbus, OH), Alicia Bao (Department of Molecular Genetics, Center for RNA Biology, OSU, Columbus, OH), Lauren Peltier (Department of Molecular Genetics, Center for RNA Biology, OSU, Columbus, OH), Anita K. Hopper (Department of Molecular Genetics, Center for RNA Biology, OSU, Columbus, OH)
Abstract:
In S. cerevisiae, 10 tRNA families are encoded by intron-containing genes. Precursor tRNAs are processed into mature functional tRNAs via several steps, including intron removal by the tRNA splicing endonuclease complex. After splicing, the free introns are rapidly and efficiently degraded. The mechanism for tRNA intron turnover has been delineated for two of the 10 families; tRNAIleUAU and tRNALeuCAA linear introns are degraded by the 5’ to 3’ exonuclease Xrn1 after 5’ phosphorylation by the tRNA ligase/kinase Rlg1(Trl1). There are at least 4 additional pathways for the remaining 8 tRNA families: Xrn1-independent, Rlg1-independent, Xrn1 and Rlg1-independent, and an endonuclease-dependent pathway for the circular form of the tRNATrp intron. To discover gene products functioning in these unknown pathways, we conducted a candidate screen of 60 mutant S. cerevisiae strains that are defective in annotated genes involved in RNA degradation and/or RNA phosphorylation. We identified several candidates as participants in tRNA family-specific intron turnover, including the 3’ to 5’ nuclease Rrp4, the endonuclease Las1, and the 5’ to 3’ nuclease regulator Met22. We also investigated the effects of various environmental stresses upon tRNA intron levels and surprisingly uncovered stress-specific, tRNA family-specific intron accumulation. Treatment of wild-type cells with 3mM H2O2 causes 15- and 8-fold elevations of tRNATrpCCA and tRNALeuCAA intron levels, respectively. Accumulation of these tRNA introns occurs for >2 hours, despite immediate termination of tRNA transcription upon oxidative stress. Inversely, most tRNA intron levels decrease with 5% ethanol or 42˚C heat treatment. One exception is tRNAProUGG which accumulates an aberrantly migrating intron upon heat stress. Our studies provide insight into family-specific endogenous and stress-induced intron turnover pathways that indicate possible novel regulatory functions of tRNA introns.
References:
1. Wu, J., & Hopper, A. K. (2014). Healing for destruction: tRNA intron degradation in yeast is a two-step cytoplasmic process catalyzed by tRNA ligase Rlg1 and 5'-to-3' exonuclease Xrn1. Genes & development, 28(14), 1556–1561. https://doi.org/10.1101/gad.244673.114
Keywords: tRNA turnover, intron degradation, environmental stress