Genotoxic therapy such as radiation serves as a frontline cancer treatment, yet acquired resistance that leads to tumor reoccurrence is frequent. We found that cancer cells maintain viability during irradiation by reversibly increasing genome-wide DNA breaks, thereby limiting premature mitotic progression. We identify caspase-activated DNase (CAD) as the nuclease inflicting these de novo DNA lesions at defined loci, which are in proximity to chromatin-modifying CCCTC-binding factor (CTCF) sites. CAD nuclease activity is governed through phosphorylation by DNA damage response kinases, independent of caspase activity. In turn, loss of CAD activity impairs cell fate decisions, rendering cancer cells vulnerable to radiation-induced DNA double-strand breaks. Our observations highlight a cancer-selective survival adaptation, whereby tumor cells deploy regulated DNA breaks to delimit the detrimental effects of therapy-evoked DNA damage.
Up to 15% of human cancers maintain their telomeres through a telomerase-independent mechanism, termed "alternative lengthening of telomeres" (ALT) that relies on homologous recombination between telomeric sequences. Emerging evidence suggests that the recombinogenic nature of ALT telomeres results from the formation of RNA:DNA hybrids (R-loops) between telomeric DNA and the long-noncoding telomeric repeat-containing RNA (TERRA). Here, we show that the mismatch repair protein MutSβ, a heterodimer of MSH2 and MSH3 subunits, is enriched at telomeres in ALT cancer cells, where it prevents the accumulation of telomeric G-quadruplex (G4) structures and R-loops. Cells depleted of MSH3 display increased incidence of R-loop-dependent telomere fragility and accumulation of telomeric C-circles. We also demonstrate that purified MutSβ recognizes and destabilizes G4 structures in vitro. These data suggest that MutSβ destabilizes G4 structures in ALT telomeres to regulate TERRA R-loops, which is a prerequisite for maintenance of telomere integrity during ALT.
- MeSH
- DNA metabolismus MeSH
- homeostáza telomer MeSH
- lidé MeSH
- nádory * genetika MeSH
- R-smyčka MeSH
- RNA dlouhá nekódující * metabolismus MeSH
- telomery metabolismus MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
Research on repurposing the old alcohol-aversion drug disulfiram (DSF) for cancer treatment has identified inhibition of NPL4, an adaptor of the p97/VCP segregase essential for turnover of proteins involved in multiple pathways, as an unsuspected cancer cell vulnerability. While we reported that NPL4 is targeted by the anticancer metabolite of DSF, the bis-diethyldithiocarbamate-copper complex (CuET), the exact, apparently multifaceted mechanism(s) through which the CuET-induced aggregation of NPL4 kills cancer cells remains to be fully elucidated. Given the pronounced sensitivity to CuET in tumor cell lines lacking the genome integrity caretaker proteins BRCA1 and BRCA2, here we investigated the impact of NPL4 targeting by CuET on DNA replication dynamics and DNA damage response pathways in human cancer cell models. Our results show that CuET treatment interferes with DNA replication, slows down replication fork progression and causes accumulation of single-stranded DNA (ssDNA). Such a replication stress (RS) scenario is associated with DNA damage, preferentially in the S phase, and activates the homologous recombination (HR) DNA repair pathway. At the same time, we find that cellular responses to the CuET-triggered RS are seriously impaired due to concomitant malfunction of the ATRIP-ATR-CHK1 signaling pathway that reflects an unorthodox checkpoint silencing mode through ATR (Ataxia telangiectasia and Rad3 related) kinase sequestration within the CuET-evoked NPL4 protein aggregates.
- MeSH
- adaptorové proteiny signální transdukční metabolismus MeSH
- ATM protein antagonisté a inhibitory metabolismus MeSH
- checkpoint kinasa 1 metabolismus MeSH
- disulfiram farmakologie MeSH
- DNA vazebné proteiny metabolismus MeSH
- jaderné proteiny antagonisté a inhibitory metabolismus MeSH
- lidé MeSH
- nádorové buněčné linie MeSH
- nádory metabolismus patologie MeSH
- odvykací prostředky alkoholu farmakologie MeSH
- patologická konformace proteinů chemicky indukované MeSH
- poškození DNA účinky léků MeSH
- protein obsahující valosin metabolismus MeSH
- proteinové agregáty účinky léků MeSH
- replikace DNA účinky léků MeSH
- signální transdukce účinky léků MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
The Golgi apparatus consists of disc-like cisternae, stretching around the nucleus through forces exerted by F-actin and the Golgi membrane protein GOLPH3. Farber-Katz et al. now report that DNA damage triggers Golgi dispersal and inhibits vesicular transport through DNA-PK-mediated GOLPH3 phosphorylation, thereby linking the DNA damage response to Golgi regulation.
- MeSH
- Golgiho aparát metabolismus MeSH
- lidé MeSH
- membránové proteiny metabolismus MeSH
- myosiny metabolismus MeSH
- poškození DNA * MeSH
- proteinkinasa aktivovaná DNA metabolismus MeSH
- zvířata MeSH
- Check Tag
- lidé MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- komentáře MeSH
- práce podpořená grantem MeSH
ATR controls chromosome integrity and chromatin dynamics. We have previously shown that yeast Mec1/ATR promotes chromatin detachment from the nuclear envelope to counteract aberrant topological transitions during DNA replication. Here, we provide evidence that ATR activity at the nuclear envelope responds to mechanical stress. Human ATR associates with the nuclear envelope during S phase and prophase, and both osmotic stress and mechanical stretching relocalize ATR to nuclear membranes throughout the cell cycle. The ATR-mediated mechanical response occurs within the range of physiological forces, is reversible, and is independent of DNA damage signaling. ATR-defective cells exhibit aberrant chromatin condensation and nuclear envelope breakdown. We propose that mechanical forces derived from chromosome dynamics and torsional stress on nuclear membranes activate ATR to modulate nuclear envelope plasticity and chromatin association to the nuclear envelope, thus enabling cells to cope with the mechanical strain imposed by these molecular processes.
- MeSH
- ATM protein metabolismus MeSH
- buňky NIH 3T3 MeSH
- chromatin metabolismus MeSH
- fibroblasty cytologie metabolismus MeSH
- HeLa buňky MeSH
- jaderný obal metabolismus MeSH
- kontrolní body buněčného cyklu MeSH
- lidé MeSH
- mechanický stres * MeSH
- myši MeSH
- nádorové buněčné linie MeSH
- osmóza MeSH
- proteinkinasy metabolismus MeSH
- zvířata MeSH
- Check Tag
- lidé MeSH
- myši MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
