Project description:Ribosomal RNAs (rRNAs) are essential components of the ribosome and are among the most abundant macromolecules in the cell. To ensure high rRNA level, eukaryotic genomes contain dozens to hundreds of rDNA genes, however, only a fraction of the rRNA genes seems to be active, while others are transcriptionally silent. In Drosophila rDNA units damaged by insertions of retrotransposons are repressed by an unknown mechanism. Here, we established a new model to study regulation of rDNA expression using molecularly marked rDNA transgenes. Using this model, we show that insertion of any heterologous sequence into rDNA leads to transcriptional repression. We found that SUMO (Small Ubiquitin-like Modifier) is required for efficient repression of damaged rDNA units. Surprisingly, SUMO also controls expression of intact rDNA, demonstrating that a single pathway is responsible for both selective repression of damaged units and silencing of surplus rDNA.
Project description:This experiment captures the expression of genes between two sites of human cartilage within the same patients to allow investigation of genomic responses to damage during osteoarthritis. Eight patients with symptomatic OA undergoing total knee replacement (n=8, age range 65-79 years, mean age 70.3) were used in this study. Cartilage from paired osteochondral samples were isolated from the intact PLC (posterior lateral condyle) and the damaged DMC (distal medial condyle) for RNA-seq analysis.
Project description:In Drosophila, Piwi-induced transcriptional repression is associated with the establishment of repressive chromatin marks by the histone methyltrasferase SetDB1, however how the Piwi/piRNA complex recruits this effector to chromatin targets is poorly understood. We identified a new player in piRNA-guided transcriptional silencing encoded by the Su(var)2-10 gene. Su(var)2-10 is required for transcriptional silencing and deposition of repressive chromatin marks on transposons and it physically associates with the Piwi/piRNA target recognition complex. Recruitment of Su(var)2-10 to a target locus in a piRNA-independent fashion induces transcriptional repression and deposition of the H3K9 trimethyl mark by the histone methyltransferase dSetDB1/Eggless. Su(var)2-10 belongs to a conserved family of proteins that function as SUMO E3 ligases and we found that the SUMO pathway is essential for the repressive function of Su(var)2-10 and for transcriptional repression of transposons. Together, our data identifies Su(var)2-10 as an essential component of the piRNA-induced transcriptional silencing pathway that links the target recognition complex to the silencing effector and reveals a novel role of SUMO modification in the piRNA-induced repression.
Project description:The uploaded data are described within "Screen Identifies DYRK1B Network as Mediator of Transcription Repression on Damaged Chromatin". In short, peptides from RPE1 epithelial cells with either normal expression of DYRK1B, over expression, of knockout of the kinase were TMT11 plex labeled and enriched by tandem phosphopeptide enrichment.
Project description:The SUMO-like domains-containing family of proteins to which Saccharomyces cerevisiae Esc2 belongs facilitates DNA damage tolerance (DDT) via elusive mechanisms. Here we report that Esc2 promotes recombination-mediated DDT by engaging in functional and physical interactions with Srs2 and Elg1, two readers of SUMOylated PCNA and modulators of DDT. These interactions depend on the SUMO Interacting Motifs of Elg1 and Srs2, and on the SUMO-like domains of Esc2. Mechanistically, Esc2 promotes Elg1 association to damaged and stalled forks and Srs2 turnover. Elg1 limits the levels of SUMOylated PCNA and subsequently of the anti-recombinase Srs2 at damaged sites, upholding local Rad51 binding. In conjunction with the SUMO–targeted ubiquitin ligase Slx5/Slx8, Esc2 also promotes proteasome-mediated Srs2 turnover, a process further enhanced by CDK-mediated Srs2 phosphorylation. Our results provide mechanistic insights into how SUMO- and DNA damage response-regulated pathways intersect to enable local error-free damage-bypass by recombination in the face of genotoxic stress. Proteins ChIP-chip analyses analysis were carried out as described (Bermejo et al., 2009). Labelled probes were hybridized to Affymetrix S.cerevisiae Tiling 1.0 (P/N 900645) arrays and processed with TAS software.
Project description:Induction of DNA double-strand breaks (DSBs) in ribosomal DNA (rDNA) repeats is associated with ATM-dependent repression of ribosomal RNA synthesis and large-scale reorganization of nucleolar architecture, but the signaling events that regulate these responses are largely elusive. Here we show that the nucleolar response to rDNA breaks is dependent on both ATM and ATR activity. We further demonstrate that ATM- and NBS1-dependent recruitment of TOPBP1 in the nucleoli is required for inhibition of ribosomal RNA synthesis and nucleolar segregation in response to rDNA breaks. Mechanistically, TOPBP1 recruitment is mediated by phosphorylation-dependent interactions between three of its BRCT domains and conserved phosphorylated Ser/Thr residues at the C-terminus of the nucleolar phosphoprotein Treacle. Our data thus reveal an important cooperation between TOPBP1 and Treacle in the signaling cascade that triggers transcriptional inhibition and nucleolar segregation in response to rDNA breaks.
Project description:Transcription factors represent one of the largest groups of proteins regulated by SUMO, and their modification has generally been correlated with transcriptional repression. However, as most of the studies focus on specific sumoylated transcriptional regulators, the distribution and global role of SUMO on chromatin in relation to transcription regulation remain largely unknown. To investigate this role, we determined the occupancy of SUMO machinery proteins on chromatin by ChIP coupled to sequencing in human primary cells. Examination of 3 histone modifications, Polymerase II, SUMO1, SUMO2, Ubc9 and PIASy in proliferative and Ras-induced senescent fibroblasts.