Poster abstracts
Poster number 134 submitted by Paolo Sinopoli
tRNA introns act as novel noncoding regulatory RNAs
Paolo L. Sinopoli (Department of Molecular Genetics, The Ohio State University), Regina T. Nostramo (Department of Molecular Genetics, The Ohio State University), Alicia Bao (College of Medicine, The Ohio State University), Sara Metcalf (Department of Molecular Genetics, The Ohio State University), Anita K. Hopper (Department of Molecular Genetics, The Ohio State University)
Abstract:
tRNAs are created through transcription of tRNA genes, a subset of which contain introns. Canonically, tRNA introns are removed during tRNA maturation and rapidly degraded. However, we have uncovered multiple lines of evidence suggesting that tRNA introns possess biological functions. First, in Saccharomyces cerevisiae tRNA introns are turned over by a minimum of five distinct degradation pathways and turnover is regulated in stress and family-specific manners. Second, the sequences of some tRNA introns in S. cerevisiae have remarkable levels of complementarity to ORFs in the genome. For instance, the tRNAIle intron possesses ≥14 nucleotides of perfect complementarity to six different ORFs. Out of 100 random sequences generated at the same length as tRNAIle intron, none have complementarity to as many ORFs as the tRNAIle intron. Third, complementarity to ORFs is regionalized to tRNA introns, with tRNA exons having none or minimal complementarity. The data lead us to propose that tRNA introns in S. cerevisiae interact with mRNA sequences similarly to regulatory microRNAs that are found in other organisms. To test the hypothesis, we generated a strain of S. cerevisiae that lacks the tRNAIle introns from both tRNAIle genes (IleiΔ). In the IleiΔ strain, there are significant increases in levels of mRNAs with complementarity to the tRNAIle intron, but not for mRNAs lacking complementarity. In contrast, a tom70Δ strain that accumulates intron-containing tRNAs in the cytoplasm possesses significantly decreased levels of the mRNAs with complementarity to tRNA introns. However, there is minimal impact on mRNAs lacking complementarity. The IleiΔ and the tom70Δ data indicate that tRNA introns have a complementarity-dependent inhibitory effect on mRNA levels. Together our findings support the model that introns housed in pre-tRNAs act as a new class of regulatory non-coding RNAs. We are currently testing the consequences of free introns in regulating mRNAs with complementarity.
Keywords: tRNA, tRNA introns, regulatory RNAs