Project description:Numerous studies over the past decade have elucidated a substantial set of long intergenic noncoding RNAs (lincRNAs). It has since become clear that lincRNAs constitute an important layer of genome regulation across a wide spectrum of species. Yet, the factors governing their evolution and origins remain relatively unexplored. One possible factor that may have shaped lincRNA biology are transposable elements (TEs). Here we set out to comprehensively characterize the TE content of lincRNAs relative to genomic averages and protein coding transcripts. Our analysis of the TE composition across 9241 human lincRNAs revealed that, in sharp contrast to protein coding genes, a striking majority (83%) of lincRNAs contain a TE, and TEs comprise 42% of lincRNA transcript sequences. LincRNA TE composition varies significantly from genomic averages, being depleted of LI and Alu elements and enriched for a broad class of endogenous retroviruses (ERVs). Furthermore, specific TE families occur in biased positions and orientations within lincRNAs, particularly at their transcription start sites, suggesting a role in the origin of those lincRNAs. Finally, we find that TEs can drive gene expression regulation of lincRNAs—we observed a dramatic correlation between lincRNAs containing HERVH elements and almost exclusive expression in pluripotent cells. Conversely, those lincRNAs that are devoid of TEs are more highly expressed in testis. Collectively, TEs pervade lincRNAs and have shaped lincRNA evolution and function via bestowing tissue-specific expression from donated transcriptional regulatory signals. We extracted profiled the transcriptome expression polyadenylated mRNA-Seq. We then used these to reconstruct the transcriptome using de-novo assemblers and identify long non coding RNAs and their expression.
Project description:Piwi-interacting RNAs (piRNAs) are ~24-30 nucleotide regulatory RNAs that are abundantly expressed in gonads. The most well-understood piRNAs mediate post-transcriptional defense against transposable elements (TEs), and derive from sense or antisense strands as a consequence of "ping-pong" amplification of complementary sequences of active TEs and piRNA master control transcripts. Another class of piRNAs, such as those expressed in pachytene testis, derive from large intergenic clusters that are strictly single-stranded. Here, we report a third substrate that generates abundant primary piRNAs. In somatic follicle cells of Drosophila ovaries, we cloned >1 million piRNAs from thousands of messenger RNAs, and these were quite preferentially derived from 3' untranslated regions. This segregation implies a competition between the translation machinery and primary piRNA biogenesis machinery for mRNA access. 3 replicates.
Project description:Transposable elements (TEs) and repetitive sequences comprise over 40% of rice genome. Different TEs are tightly regulated by distinct epigenetic mechanisms. For example, the activities of LTR retrotransposon Tos17 and non-LTR retrotransposon LINE element Karma are uniquely regulated by histone H3K9 methylation and histone H3K4 demethylation, respectively. Miniature inverted repeat transposable elements (MITEs) are one of the most high-copy-number DNA transposons, which are interspersed around rice genome and might influence nearby gene expression. In plants, 24-nucleotide (24-nt) heterochromatic small interfering RNAs (hc-siRNAs) derived from repeats and TEs. To what extent hc-siRNA associated TEs affect gene expression and therefore contribute to agricultural traits in rice remains elusive. Here, we show that OsDCL3a, one of Dicer-Like 3 (DCL3) homolog, is primarily responsible for 24-nt hc-siRNA processing in rice. Impaired OsDCL3a displayed altered important agricultural traits in rice. We found that genome-wide (281,563) 24-nt hc-siRNA clusters were OsDCL3a-dependent, among which MITEs were significantly enriched. Impaired OsDCL3a caused significant overlapping between reduced hc-siRNAs from MITEs and elevated nearby gene expression. Intriguingly, genes involved in Gibberellin and Brassinosteroid homeostasis were identified as direct targets of OsDCL3a, which may attribute to dwarfism and enlarged flag leaf angle upon OsDCL3a deficiency. Our work uncovers OsDCL3a-dependent hc-siRNAs derived from MITEs as broad spectrum of regulators for fine-tuning gene expression, and this observation may reflect a conserved mechanism in other higher plants with dispersed repeat- or TE-rich genomes. Examination of OsDCL3a-dependent hc-siRNAs derived from MITEs.
Project description:RNA-directed DNA methylation (RdDM) is a transcriptional silencing mechanism mediated by small and long noncoding RNAs produced by the plant-specific RNA polymerases Pol IV and Pol V, respectively. Through a chemical genetics screen with a luciferase-based DNA methylation reporter, LUCL, we found that camptothecin, a compound with anti-cancer properties that targets DNA topoisomerase 1a (TOP1a) was able to de-repress LUCL by reducing its DNA methylation and H3K9 dimethylation (H3K9me2) levels. Further studies with Arabidopsis top1a mutants showed that TOP1a promotes RdDM by facilitating the production of Pol V-dependent long non-coding RNAs, AGONAUTE4 recruitment and H3K9me2 deposition at transposable elements (TEs). 5 small RNA libraries were sequenced
Project description:To investigate the impact of disruption of the non-CG DNA methylation/H3K9me2 pathway upon transcription in Arabidopsis, we performed RNA-seq using meiotic-stage floral buds from wild type (Col-0) and kyp/suvh4 suvh5 suvh6 mutant plants. This enabled identification of differentially expressed genes and transposable elements (TEs). TEs that were up-regulated in kyp/suvh4 suvh5 suvh6 relative to wild type were evaluated for over-representation of elements within each TE family.
Project description:Long time considered as « junk DNA », the evolutive force of transposable elements (TEs) is now well established and TEs contribute strongly to eukaryote genome plasticity. However, it is difficult to fully characterize the mobile part of a genome, or active mobilome, and tracking TE activity remains challenging. He we have applied the detection of extrachromosomal circular DNA (mobilome-seq) as a diagnostic for plant TE activity on Poplar mersitems from WT and ddm1 RNAi plants grown in normal or hydric stress conditions.
