Project description:Despite a vast expansion in the availability of epigenomic data, our knowledge of the chromatin landscape at interspersed repeats remains highly limited by difficulties in mapping short-read sequencing data to these regions. In particular, little is known about the locus-specific regulation of evolutionarily young transposable elements (TEs), which have been implicated in genome stability, gene regulation and innate immunity in a variety of developmental and disease contexts. Here we propose an approach for generating locus-specific protein-DNA binding profiles at interspersed repeats, which leverages information on the spatial proximity between repetitive and non-repetitive genomic regions. We demonstrate that the combination of Hi-ChIP and a newly developed mapping tool (PAtChER) yields accurate protein enrichment profiles at individual repetitive loci. Using this approach, we show that young TEs display locus- and tissue-specific chromatin profiles in both mice and humans. Insights gained using our method will be invaluable for dissecting the molecular determinants of TE regulation and their impact on the genome.
Project description:Despite a vast expansion in the availability of epigenomic data, our knowledge of the chromatin landscape at interspersed repeats remains highly limited by difficulties in mapping short-read sequencing data to these regions. In particular, little is known about the locus-specific regulation of evolutionarily young transposable elements (TEs), which have been implicated in genome stability, gene regulation and innate immunity in a variety of developmental and disease contexts. Here we propose an approach for generating locus-specific protein-DNA binding profiles at interspersed repeats, which leverages information on the spatial proximity between repetitive and non-repetitive genomic regions. We demonstrate that the combination of Hi-ChIP and a newly developed mapping tool (PAtChER) yields accurate protein enrichment profiles at individual repetitive loci. Using this approach, we show that young TEs display locus- and tissue-specific chromatin profiles in both mice and humans. Insights gained using our method will be invaluable for dissecting the molecular determinants of TE regulation and their impact on the genome.
Project description:Transposable elements (TEs) serve as both insertional mutagens and regulatory elements in cells, and their aberrant activity is increasingly being revealed to contribute to diseases and cancers. However, measuring the transcriptional consequences of nonreference and young TEs at individual loci remains challenging with current methods, primarily due to technical limitations, including short read lengths generated and insufficient coverage in target regions. Here, we introduce a long-read targeted RNA sequencing method, Cas9-assisted profiling TE expression sequencing (capTEs), for quantitative analysis of transcriptional outputs for individual TEs, including transcribed nonreference insertions, noncanonical transcripts from various transcription patterns and their correlations with expression changes in related genes. This method selectively identified TE-containing transcripts and outputted data with up to 90% TE reads, maintaining a comparable data yield to whole-transcriptome sequencing. We applied capTEs to human cancer cells and found that internal and inserted Alu elements may employ distinct regulatory mechanisms to upregulate gene expression.
Project description:Establishing and maintaining phenotypic heterogeneity within cell and organismal populations is an evolutionarily conserved strategy that ensures survival of the population following stressful exposures. We previously identified a transient, reversible, drug-tolerant cancer cell subpopulation that survives otherwise lethal drug exposures. Here we show that these drug-tolerant persisters (DTPs) assume a highly heterochromatic state, which requires factors that modify or bind trimethylated H3 lysine 9 (H3K9me3). The increased H3K9me3 in DTPs is largely restricted to evolutionarily young Long Interspersed Repeat elements (LINEs). This transcriptionally repressive state, which decreases the expression of these retrotransposable elements, is critical for DTP survival, and disruption of this heterochromatic state results in re-expression of LINE elements and ablation of this subpopulation. Together, these findings establish a role for epigenetic silencing of transposable elements as a population survival strategy to maintain genomic integrity in subpopulations of cancer cells during lethal drug exposures.
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.