Poster abstracts

Poster number 1 submitted by Andrea McCue

Transposable Element Small RNAs as Regulators of Gene Expression

Andrea D. McCue (Molecular Genetics, The Ohio State University), R. Keith Slotkin (Molecular Genetics, The Ohio State University)

Abstract:
Transposable elements (TEs) are mobile fragments of DNA that occupy large fractions of eukaryotic genomes. Their ability to move makes them potent mutagens, and eukaryotes have evolved elaborate mechanisms of TE repression that utilize small RNAs (sRNAs) to direct heterochromatic epigenetic modifications to TE sequences. This mode of TE silencing is conserved from plants to mammals and has well-documented effects on the regulation of TE-neighboring genes in cis. My research has uncovered a novel mechanism of TE regulation of genes in trans, whereby an Arabidopsis thaliana TE represses a non-TE-neighboring gene via a TE sRNA, resulting in altered regulation of the cellular stress response. A class of Arabidopsis sRNAs accumulate only under conditions of genome-wide transcriptional reactivation of TEs. We provide direct evidence that one of these sRNAs, siRNA854, post-transcriptionally regulates the non-TE gene, UBP1b. We are the first to demonstrate that the epigenetic regulation of a TE can lead to the regulation of a gene in trans, mediated by a TE sRNA. This work blurs the lines between TE-derived and gene-regulating sRNAs, a distinction that is prevalent in the current literature.
Based on this research, we hypothesized that a genome-wide mechanism of gene regulation exists in which TE-derived sRNAs act to alter global gene regulation under conditions of transcriptionally active TEs. To test this hypothesis, I paired sRNA deep sequencing with microarray analysis of wild-type and mutant plants, which lose global epigenetic regulation of TEs, in order to find candidate TE-derived sRNAs that putatively target non-TE genes. The relationship between TE sRNAs and putative target candidates was further analyzed to obtain a small list of candidates on which to focus future experiments. We believe that post-transcriptional regulation of genes by TE sRNAs may contribute to the changes in gene expression and phenotype observed in plants and animals during viral infection and/or progressive loss of heterochromatin, as new TE and viral small RNAs and new unexplained phenotypes are abundant under these conditions.

Keywords: small RNA, transposable elements, post-transcriptional gene regulation