Poster abstracts
Poster number 104 submitted by Gina Nostramo
Do tRNA introns have a biological function?
Regina Nostramo (Department of Molecular Genetics, Center for RNA Biology, The Ohio State University), Alicia Bao (Department of Molecular Genetics, The Ohio State University), Lauren Peltier (Department of Molecular Genetics, The Ohio State University), Anita K. Hopper (Department of Molecular Genetics, Center for RNA Biology, The Ohio State University)
Abstract:
A subset of genes encoding tRNAs contain introns. In most species, tRNA introns are located 3’ to the anticodon and are removed from pre-tRNAs by the tRNA splicing endonuclease. Pre-tRNA splicing is essential in most organisms because, for at least one tRNA family, all reiterated tRNA genes contain an intron. Thus, the genome cannot be decoded without tRNA splicing. Why has the possession of tRNA introns been conserved from archaea to vertebrates? One possibility is that the released introns serve biological roles. In support of this, we found that there are at least 5 pathways for tRNA intron turnover in budding yeast, and that although normally degraded, various stressors cause tRNA- and stress-specific tRNA intron accumulation. Further, sequence analysis reveals that some tRNA introns possess long stretches of complementarity to sequences in or around ORFs. The existence of these “tRNA intron complementarity (TIC) sequences” raises the possibility that particular tRNA introns may function as novel non-coding RNAs in the regulation of gene expression. To test this hypothesis, we are employing 3 different strategies. First, we are generating yeast strains lacking a specific species of tRNA intron. Second, we are adding stressors known to modulate tRNA intron levels. Lastly, we are incorporating synonymous codons into the TIC sequence of mRNAs. Sequence analysis of the mRNA for ORC2 reveals 14bp of perfect complementarity to the tRNAIleUAU intron in its ORF. Endogenous deletion of the introns from the tRNAIleUAU genes decreased Orc2-GFP protein, without a concomitant change in its mRNA, despite the fact that proteins of all non-TIC sequence containing genes examined were unaltered. These findings suggest the exciting possibility that the tRNAIleUAU intron may act post-transcriptionally and sequence-specifically to positively regulate Orc2 levels. Overall, these data indicate that tRNA introns may be the newest member of non-coding regulatory RNAs.
Keywords: tRNA, introns, gene expression