Project description:Transposable elements are genomic parasites that expand within and spread between genomes. Piwi proteins control transposon activity, notably in the germline. These proteins recognize their targets through small RNA co-factors named piRNAs, making piRNA biogenesis a key specificity-determining step in this important genome immunity system. While the processing of piRNA precursors is an essential step in this process, many molecular details of this process remain unknown. We identify a novel endoribonuclease, PUCH, that initiates piRNA processing in the nematode Caenorhabditis elegans. Genetic and biochemical studies show that PUCH, a trimer of Schlafen-like-domain (SLFNL) proteins, executes 5ï‚¢-end piRNA precursor cleavage. PUCH-mediated processing strictly requires an m7G-Cap and a Uracil at position three. We also demonstrate how PUCH interacts with PETISCO, a complex that binds piRNA precursors, and that this interaction enhances piRNA production in vivo. The identification of PUCH completes the C. elegans piRNA biogenesis repertoire and uncovers a novel type of RNA endonuclease formed by three SLFL proteins. Mammalian Slfn genes have been associated with immunity responses, exposing a novel molecular link between immune responses in mammals and deeply conserved RNA-based mechanisms that control transposable elements.
Project description:Background: Transposable elements are known to influence the regulation of some genes. We aimed to determine which genes show altered gene expression when transposable elements are epigenetically activated. Results: We find over 2000 genes with altered steady-state expression levels in ddm1 mutants. Some of these genes are influenced by neighboring transposable element fragments, while other genes are targeted by transposable element derived 21 nucleotide siRNAs. Conclusion: The regulation of the genic portion of the Arabidopsis genome is heavily influenced by the epigenetic regulation of transposable elements. The regulation of genes by transposable elements can occur through multiple mechanisms. Three biological replicates for two genotypes
Project description:Transposable elements hold regulatory functions to impact cell fate determination by controlling gene expression, which when altered can promote oncogenesis. Despite accounting for half of the human genome, little is known about the transcriptional mechanisms that confer regulatory properties to transposable elements in pluripotent, mature versus oncogenic cell states. Through positional analysis over repetitive DNA sequence of H3K27ac ChIP-seq from 32 different normal cell and tissue states, we report pluripotent stem and mature cell states-specific “regulatory transposable elements”. Those specific to pluripotent stem cells are binding sites for the pluripotency factors NANOG, SOX2 and OCT4. In mature cell and tissue states, regulatory transposable elements are docking sites for lineage-specific transcription factors, such as AR and FOXA1 in benign prostate epithelium. Expanding the positional analysis to localized prostate tumors, we show how cancer cell states remaining dependent on AR share regulatory transposable elements with pluripotent stem cells. These include regulatory transposable elements, such as Tigger3a, that serve as binding sites for AR and whose regulatory functions are required for prostate cancer cell growth. Together, our results suggest that oncogenesis differs from normal cell fate determination by hijacking pluripotent stem cells regulatory transposable elements that serve as docking sites for lineage-specific transcription factors.