Project description:Multiple replication abnormalities cause cells lacking BRCA2 to enter mitosis with under-replicated DNA and to activate mitotic DNA synthesis (MiDAS). However, the precise position of these MiDAS sites, as well as their origin, remains unknown. Here we labelled mitotic nascent DNA and performed high-throughput sequencing to identify at high-resolution the sites where MiDAS occurs in the absence of BRCA2. This approach revealed 150 genomic loci affected by MiDAS, which map within regions replicating during early S-phase and are therefore distinct from the aphidicolin-induced common fragile sites. Moreover, these sites largely localise near early firing origins and within genes transcribed in early S, suggesting that they stem from transcription-replication conflicts (TCRs). Inhibiting transcription with 5,6-dichloro-1-β-D-ribofuranosylbenzimidazole (DRB) during early S-phase abrogates MiDAS. Strikingly, MiDAS sites co-localise with genomic loci where R-loops form in unchallenged conditions, suggesting that R-loop accumulation caused by BRCA2 inactivation leads to DNA lesion which are repaired by MiDAS. RAD52 is required in this process, as its abrogation in BRCA2-deficient cells reduces the rate of MiDAS and causes DNA damage accumulation in G1. Furthermore, MiDAS sites triggered by BRCA2 inactivation are hotspots for genomic rearrangement in BRCA2-mutated breast tumours. These results indicate that BRCA2 acts in early S-phase to protect TRC- and R-loop-induced DNA lesions, thereby preventing them from becoming a source of genomic instability and tumorigenesis.
Project description:DNA replication stress is an established driver of cancer-associated chromosomal rearrangements. Replication stress perturbs the duplication of late-replicating loci and activates a mitotic DNA repair pathway (termed MiDAS) for completion of replication. We here investigated RAD51-independent MiDAS.
Project description:This 133-node Boolean regulatory network model reproduces mitochondrial dynamics during cell cycle progression (hyper-fusion at the G1/S boundary, fission in mitosis), apoptosis (fission and dysfunction) and glucose starvation (reversible hyper-fusion), as well as MiDAS in response to SIRT3 knockdown or oxidative stress and the protective role of NAD+ or external pyruvate. These features are in addition to the cell cycle-related phenotypes reproduced by the Sizek et al model that served as our starting point. Testable predictions (new): a) In cell lines with low basal p21 expression known to pre-commit to the next division in early mitosis of their current cycle, a subset of cells respond to glucose withdrawal by arresting with 4N DNA content but losing their internal G2 state (i.e. Cyclin A/B expression), and undergo endo-reduplication upon glucose re-exposure. b) In a subset of glucose-starved cells that pass the G2/M checkpoint with hyperfused mitochondria, mitotic fragmentation can be sufficiently delayed to cause spindle assembly defects and mitotic catastrophe. c) Quiescent cells are less susceptible to ROS-induced MiDAS due to FoxO-mediated PINK1 expression, which blocks MFN1/2 from inducing hyperfusion. d) Boosting NAD+ levels in MiDAS cells that have not yet established deep senescence (2-3 days post induction) can reverse their fate.
Project description:The experimental project studied a MIDAS adhesin minus mutant of predatory bacterium B. bacteriovorus.The predatory bacterium normally invades and lives inside E.coli bacteria, rounding them up to form a two-bacterial structure, called a bdelloplast, and killing the E.coli from the inside. However the MIDAS mutant predator failed to invade in 10% of cases due to one of its (many) attachment/invasion mechanisms being absent. We enriched and purified the 10% of bdelloplasts which did not have an invaded predator inside, by Percoll gradient centrifugation. Although these bdelloplasts did not have an invaded predator they were still rounded and dead. We sent the bdelloplast sample for total protein content analysis at the Oxford Advanced Proteomics Facility. We found that although the bdelloplasts areE.coli cells they also contain secreted Bdellovibrio proteins that normally an invading wild type Bdellovibrio is known to secrete into their prey, during invasion. This suggests that a short-lived failed attachment allowed the Bdellovibrio to secrete in predatory proteins , even though it failed to enter the E.coli, and that those predatory proteins alone were enough to round and kill it.
Project description:DNA replication stress promotes cancer development and is associated with DNA synthesis beyond S-phase. Replication stress-induced DNA lesions and under-replicated DNA can persist into G2 and mitosis, where they undergo mitotic DNA synthesis (MiDAS). After cell division, inherited DNA lesions are protected by genome caretaker proteins and show signs of post-mitotic DNA synthesis (post-MiDAS) in G1. The genomic regions that undergo post-MiDAS, the cellular factors involved, and the implications for genome integrity remain poorly understood. Here, we provide evidence for post-MiDAS activity at centromeres and telomeres in cancer cells employing alternative lengthening of telomeres (ALT) and present data suggesting that a subset of these fragile genomic regions can cluster during post-MiDAS in G1. We further show that post-MiDAS is promoted by local SUMOylation and BLM recruitment into ALT-associated PML bodies (APBs) and involves DNA damage tolerance factors and proteins associated with ALT and MiDAS. Consistent with G1-specific regulation, complementary quantitative proteomics and targeted siRNA screening reveal that APC/C, together with its G1 co-activator CDH1 but independent of its mitotic co-activator CDC20, restrains excessive post-MiDAS in G1. Finally, we show that CDH1 depletion selectively impairs the survival of ALT-positive cancer cell lines, indicating that post-MiDAS might represent a potential ALT-specific vulnerability. This dataset contains TurboID-RPA32 proximity labeling mass spectrometry data generated from FACS-sorted G1-phase U-2 OS FUCCI TurboID-RPA32-HA cells to identify proteins in proximity to RPA32.
Project description:DNA replication stress promotes cancer development and is associated with DNA synthesis beyond S-phase. Replication stress-induced DNA lesions and under-replicated DNA can persist into G2 and mitosis, where they undergo mitotic DNA synthesis (MiDAS). After cell division, inherited DNA lesions are protected by genome caretaker proteins and show signs of post-mitotic DNA synthesis (post-MiDAS) in G1. The genomic regions that undergo post-MiDAS, the cellular factors involved, and the implications for genome integrity remain poorly understood. Here, we provide evidence for post-MiDAS activity at centromeres and telomeres in cancer cells employing alternative lengthening of telomeres (ALT) and present data suggesting that a subset of these fragile genomic regions can cluster during post-MiDAS in G1. We further show that post-MiDAS is promoted by local SUMOylation and BLM recruitment into ALT-associated PML bodies (APBs) and involves DNA damage tolerance factors and proteins associated with ALT and MiDAS. Consistent with G1-specific regulation, complementary quantitative proteomics and targeted siRNA screening reveal that APC/C, together with its G1 co-activator CDH1 but independent of its mitotic co-activator CDC20, restrains excessive post-MiDAS in G1. Finally, we show that CDH1 depletion selectively impairs the survival of ALT-positive cancer cell lines, indicating that post-MiDAS might represent a potential ALT-specific vulnerability. This dataset contains RPA70 immunoprecipitation mass spectrometry data generated from chromatin-bound protein extracts of FACS-sorted G1-phase U-2 OS FUCCI cells to identify the interactome of RPA70 in G1.
Project description:DNA replication stress promotes cancer development and is associated with DNA synthesis beyond S-phase. Replication stress-induced DNA lesions and under-replicated DNA can persist into G2 and mitosis, where they undergo mitotic DNA synthesis (MiDAS). After cell division, inherited DNA lesions are protected by genome caretaker proteins and show signs of post-mitotic DNA synthesis (post-MiDAS) in G1. The genomic regions that undergo post-MiDAS, the cellular factors involved, and the implications for genome integrity remain poorly understood. Here, we provide evidence for post-MiDAS activity at centromeres and telomeres in cancer cells employing alternative lengthening of telomeres (ALT) and present data suggesting that a subset of these fragile genomic regions can cluster during post-MiDAS in G1. We further show that post-MiDAS is promoted by local SUMOylation and BLM recruitment into ALT-associated PML bodies (APBs) and involves DNA damage tolerance factors and proteins associated with ALT and MiDAS. Consistent with G1-specific regulation, complementary quantitative proteomics and targeted siRNA screening reveal that APC/C, together with its G1 co-activator CDH1 but independent of its mitotic co-activator CDC20, restrains excessive post-MiDAS in G1. Finally, we show that CDH1 depletion selectively impairs the survival of ALT-positive cancer cell lines, indicating that post-MiDAS might represent a potential ALT-specific vulnerability. This dataset contains RPA70 immunoprecipitation mass spectrometry data generated from whole-cell protein extracts of FACS-sorted G1-phase U-2 OS FUCCI cells to identify the interactome of RPA70 in G1.
2026-08-26 | PXD069739 | Pride
Project description:Midas cichlids Genome sequencing and assembly