Project description:Distribution of R-loops on genomic sites was studied for exponentially growing Escherichia coli in different conditions using strand-specific DRIP-Seq with S9.6 antibodies.
Project description:The goal of this study was to compare the qualitative and quantitative differences in the presence of DNA:RNA hybrids (R-loops) between chicken DT40 wild type and PrimPol knockout cells. Our initial genetic experiments on a reporter locus have showed a link between the formation of R-loop and non-B DNA motifs; we have therefore analysed the correlation between R-loop abundance and of sequences computationaly predicted to form triplex-DNA or G-quadruplex forming sequences, and whether this changes between the two cell lines.
Project description:We report the genome localization of R-loops in early and late-stage embryos relative to Drosophila cultured cells. We demonstrate that proper absolute R-loop levels chage during embryogenesis and that resolution of R-loops is critical for embryonic development. R-loop mapping by strand-specific DRIP-seq revealed that R-loop localization is plastic across development, both in the genes which form R-loops and where they localize relative to gene bodies. Importantly, these changes are not driven by changes in the transcriptional program. Rather, negative GC skew and absolute changes in AT skew are associated with R-loop formation in Drosophila. Furthermore, we demonstrate that while some chromatin binding proteins and histone modification such as H3K27me3 are associated with R-loops throughout development, other chromatin factors associated with R-loops in a developmental specific manner.
Project description:Strand asymmetry in the distribution of guanines and cytosines, measured by GC skew, predisposes DNA sequences towards R-loop formation upon transcription. Previous work revealed that GC skew and R-loop formation associate with a core set of unmethylated CpG island (CGI) promoters in the human genome. Here, we show that GC skew can distinguish four classes of promoters, including three types of CGI promoters, each associated with unique epigenetic and gene ontology signatures. In particular, we identify a strong and a weak class of CGI promoters and show that these loci are enriched in distinct chromosomal territories reflecting the intrinsic strength of their protection against DNA methylation. Interestingly, we show that strong CGI promoters are depleted from the X chromosome while weak CGIs are enriched, a property consistent with the acquisition of DNA methylation during dosage compensation. Furthermore, we identify a third class of CGI promoters based on its unique GC skew profile and show that this gene set is enriched for Polycomb group targets. Lastly, we show that nearly 2,000 genes harbor GC skew at their 3’ ends and that these genes are preferentially located in gene-dense regions and tend to be closely arranged. Genomic profiling of R-loops accordingly showed that a large proportion of genes with terminal GC skew form R-loops at their 3’-ends, consistent with a role for these structures in permitting efficient transcription termination. Altogether, we show that GC skew and R-loop formation offer significant insights into the epigenetic regulation, genomic organization, and function of human genes. DRIP-seq was performed on genomic DNA extracted from human pluripotent Ntera2 cells. The DNA was either fragmented using HindIII, EcoRI, BsrGI, XbaI and SspI (DRIP-seq 1) or BamHI, NcoI, ApaLI, NheI and PvuII (DRIP-seq 2, two technical replicates). Input DNA was also fragmented with each restriction enzyme cocktail and sequenced alongside.
Project description:We show that these R-loop objects impose specific physical constraints on the DNA, as revealed by the presence of stereotypical angles in the surrounding DNA. Biochemical probing and mutagenesis experiments revealed that the formation of R-loop objects at Airn is dictated by the extruded non-template strand, suggesting that R-loops possess intrinsic sequence-driven properties. Consistent with this, we show that R-loops formed at the fission yeast gene sum3 do not form detectable R-loop objects. Our results reveal that R-loops differ by their architectures and that the organization of the non-template strand is a fundamental characteristic of R-loops, which could explain that only a subset of R-loops is associated with replication-dependent DNA breaks.
Project description:DNA Double Strands Breaks (DSBs) are highly detrimental since they can lead to mutations and chromosomes rearrangements (amplification, deletion, translocation and chromosome loss). Here, we set to assess the role of senataxin, a RNA:DNA helicase involved in the regulation of transcription and the maintenance of genome integrity, at sites of DNA Double Strand Breaks. We performed ChIP-Seq mapping of senataxin before and after damage, genome-wide DNA:RNA hybrids (DRIP) mapping before and after damage. We also performed RNA-Seq and RNA pol II mapping (total and phosphorylated on serine 2 of the CTD) by ChIP-Seq in undamaged cells to discriminate between damage in active versus inactive regions.
Project description:Inspired by the important roles of the special chromatin structure R-loops, here we report a new method, ssDRIP-seq, for genome-wide identification of R-loops, and demonstrate its high efficiency, low bias, and strand-specificity when profiling the R-loops in Arabidopsis. Using this single-strand DNA ligation based library construction technique, we find that Arabidopsis R-loops are formed in both the sense and antisense orientations of genes, and prefer both AT and GC skews. R-loops are prevalent in regions with multiple chromatin modifications, and are negatively correlated with CG DNA hypermethylation. R-loops are strongly enriched in gene promoters and gene bodies, highly associated with noncoding RNA and repetitive genomic regions, and correlated with activated and repressed gene loci. In summary, our analysis reveals that R-loop is a common feature of the Arabidopsis genome, and suggests diverse roles for R-loops in genome organization and gene regulation, thereby providing novel insights into plant nuclear genome formation and function.
Project description:Ewing’s sarcoma family of tumors (ESFT) is an aggressive pediatric bone and soft tissue cancer. It is the prototypical example of mesenchymal tumors driven by a fusion oncogene involving the ewing sarcoma break point region 1 (EWSR1) gene, most frequently– EWS-FLI1. We have discovered that loss of EWSR1 leads to accumulation of R-loops, replication stress and impaired homologous recombination, recapitulating breast cancer 1, early onset (BRCA1) deficiency. EWS-FLI1 acts dominant negatively in ESFT to impart the same phenotypes. Further we demonstrate that in ESFT, BRCA1 predominantly associates with the elongating transcription machinery and is unavailable for DNA strand break repair. Gene expression profiling identified upregulated compensatory mechanisms in ESFT cells to process increased R-loops (RNASEH2 and FEN1) and replication stress (Fanconi Anemia). Taken together, our data identifies BRCA1 sequestration due to transcription stress as the mechanistic basis for ESFT chemosensitivity and suggests potential targets for the much lacking second-line therapy.
Project description:This study profiles RNA:DNA hybrid formation in human and mouse cell lines. DRIPc-seq (strand-specific R-loop mapping) was performed on human NT2 cells and mouse 3T3 cells. DRIP-seq (R-loop mapping) was performed on human NT2 and K562 and mouse E14 and 3T3 cell lines. MethylC-seq and RNA-seq were performed on NT2.