Project description:TrAEL-seq was performed on hydroxyurea-blocked and then released yeast cells to track replication fork stalling and replication fork restart, in wild-type and replisome mutant strains.
Project description:We have designed a methodology for capture of DNA 3’ ends that allows mapping of resected DNA breaks, stalled replication forks and also normal replication fork progression. This Transferase-activated end ligation or TrAEL-seq method involves ligation of a functionalised linker to DNA 3’ ends followed by fragmentation, purification of adaptor ligated fragments, second adaptor ligation and library amplification. The major advantages of TrAEL-seq compared to other available methods are: i) an ability to map double strand breaks after resection, ii) excellent sensitivity and signal-to-noise in detecting replication fork stalling and iii) ability to map replication fork progression in unsynchronised, unlabelled populations of both yeast and mammalian cells. The samples provided here were selected to demonstrate different aspects of TrAEL-seq activity: the SfiI and dmc1 datasets shows capture of 3’ extended single strand DNA. The other yeast datasets show replication and replication fork stalling information. The RAF and RAF-GAL grown yeast samples show the effect transcriptional induction on replication fork progression. The hESC samples show the capacity to derive replication profiles from mammalian cells.
Project description:H2B mono-ubiquitylation facilitates fork stalling and recovery during replication stress by coordinating Rad53 activation and chromatin assembly
Project description:RNA-seq was used to assess mRNA transcript abundance in wild type and fra2Δ S. cerevisiae (BY4741) cells treated with 2-(6-benzyl-2-pyridyl)quinazoline (BPQ) and CuSO4. BPQ potentiates copper toxicity and in yeast, in common with other organisms, a major cause of copper toxicity is damage of iron-sulphur clusters. Iron sensing within yeast relies on mitochondrial iron-sulphur cluster biosynthesis and therefore treatment with BPQ and copper can be used to mimic iron deficiency. Fra2 is known to be a key component of the iron sensing mechanism; however, this mechanism can operate, to an extent, independently of Fra2. BPQ (+CuSO4) treatment was used with the aim of probing the regulation of the iron regulon of S. cerevisiae and the role of Fra2 in the suppression of the low iron response. This study has uncovered nine new Cth2 target-transcripts, plus a new Aft1 target-gene and paralogous non-target. Fra2 dominates basal repression of the iron regulon in iron-replete cultures, however, Fra2-independent control of the iron regulon is also observed with CTH2 appearing to be atypically Fra2-dependent. Transcripts from untreated and CuSO4 treated cells were included as controls.
Project description:Background: Chromatin remodeling complexes facilitate the access of enzymes that mediate transcription, replication or repair of DNA by modulating nucleosome position and/or composition. Ino80 is the DNA-dependent Snf2-like ATPase subunit of a complex whose nucleosome remodeling activity requires actin-related proteins, Arp4, Arp5 and Arp8, as well as two RuvB-like DNA helicase subunits. Budding yeast mutants deficient for Ino80 function are not only hypersensitive to reagents that induce DNA double strand breaks, but also to those that impair replication fork progression. Results: To understand why ino80 mutants are sensitive to agents that perturb DNA replication, we used chromatin immunoprecipitation to map the binding sites of the Ino80 chromatin remodeling complex on four budding yeast chromosomes. We found that Ino80 and Arp5 binding sites coincide with origins of DNA replication and tRNA genes. In addition, Ino80 was bound at 67% of the promoters of genes that are sensitive to ino80 mutation. When replication forks were arrested near origins in the presence of hydroxyurea (HU), the presence of the Ino80 complex at stalled forks and at unfired origins increased dramatically. Importantly, the resumption of DNA replication after release from a HU block was impaired in the absence of Ino80 activity. Mutant cells accumulated double-strand breaks as they attempted to restart replication. Consistently, ino80-deficient cells, although proficient for checkpoint activation, delay recovery from the checkpoint response. Conclusions: The Ino80 chromatin remodeling complex is enriched at stalled replication forks where it promotes the resumption of replication upon recovery from fork arrest. Keywords: ChIP-chip
Project description:Background: Chromatin remodeling complexes facilitate the access of enzymes that mediate transcription, replication or repair of DNA by modulating nucleosome position and/or composition. Ino80 is the DNA-dependent Snf2-like ATPase subunit of a complex whose nucleosome remodeling activity requires actin-related proteins, Arp4, Arp5 and Arp8, as well as two RuvB-like DNA helicase subunits. Budding yeast mutants deficient for Ino80 function are not only hypersensitive to reagents that induce DNA double strand breaks, but also to those that impair replication fork progression. Results: To understand why ino80 mutants are sensitive to agents that perturb DNA replication, we used chromatin immunoprecipitation to map the binding sites of the Ino80 chromatin remodeling complex on four budding yeast chromosomes. We found that Ino80 and Arp5 binding sites coincide with origins of DNA replication and tRNA genes. In addition, Ino80 was bound at 67% of the promoters of genes that are sensitive to ino80 mutation. When replication forks were arrested near origins in the presence of hydroxyurea (HU), the presence of the Ino80 complex at stalled forks and at unfired origins increased dramatically. Importantly, the resumption of DNA replication after release from a HU block was impaired in the absence of Ino80 activity. Mutant cells accumulated double-strand breaks as they attempted to restart replication. Consistently, ino80-deficient cells, although proficient for checkpoint activation, delay recovery from the checkpoint response. Conclusions: The Ino80 chromatin remodeling complex is enriched at stalled replication forks where it promotes the resumption of replication upon recovery from fork arrest. Keywords: ChIP-chip
Project description:The stability of the genome is occasionally challenged by the formation of DNA-RNA hybrids and R-loops, which can be influenced by the chromatin context. This is mainly due to the fact that DNA-RNA hybrids hamper the progression of replication forks, leading to fork stalling and, ultimately, DNA breaks. Through a specific screening of chromatin modifiers performed in the yeast Saccharomyces cerevisiae, we have found that the Rtt109 histone acetyltransferase is involved in several steps of R-loop-metabolism and their associated genetic instability. On one hand, Rtt109 prevents DNA-RNA hybridization by the acetylation of histone H3 lysines 14 and 23, and on the other hand, it is involved in the repair of replication-born DNA breaks, such as those that can be caused by R-loops, by acetylating lysines 14 and 56. In addition, Rtt109 loss renders cells highly sensitive to replication stress in combination with R-loop-accumulating THO-complex mutants. Our data evidence that the chromatin context simultaneously influences the occurrence of DNA-RNA hybrid-associated DNA damage and its repair, adding complexity to the source of R-loop-associated genetic instability.