DNA double-strand breaks (DSBs) signaling and repair is crucial to preserve genomic integrity and maintain cellular homeostasis. During the response to DSBs, histone ubiquitylation by RNF168 is a critical event, which or-chestrates the recruitment of downstream effectors, e.g. BRCA1 and 53BP1. While 53BP1 licenses the non-homologous end joining (NHEJ), BRCA1 initiates the DNA resection thus enabling homologous recombination (HR). Under conditions of ubiquitin starvation, mostly resulting from proteotoxic stress, the ubiquitin-dependent accumulation of DNA damage response proteins at the sites of DNA damage is impaired. Therefore, the proteo-toxic stress is commonly manifested by an attenuation of ubiquitin-mediated DSBs response. However, we have identified several cancer cell lines that display recruitment of 53BP1 to the sites of DSBs under the conditions of pro-teasome inhibitor (Bortezomib or MG132) induced proteo-toxic stress, i.e., under substantial depletion of nuclear free ubiquitin levels. This review brings a brief description of two major DSBs repair pathways: HR and NHEJ, their functional dependency on signaling through ubiquitin and a discussion of newly identified phenomenon of proteo-toxic stress resistant response to DNA double-strand breaks.

• MeSH
• dvouřetězcové zlomy DNA * MeSH
• oprava DNA * MeSH
• ubikvitin MeSH

Hereditary mutations in polynucleotide kinase-phosphatase (PNKP) result in a spectrum of neurological pathologies ranging from neurodevelopmental dysfunction in microcephaly with early onset seizures (MCSZ) to neurodegeneration in ataxia oculomotor apraxia-4 (AOA4) and Charcot-Marie-Tooth disease (CMT2B2). Consistent with this, PNKP is implicated in the repair of both DNA single-strand breaks (SSBs) and DNA double-strand breaks (DSBs); lesions that can trigger neurodegeneration and neurodevelopmental dysfunction, respectively. Surprisingly, however, we did not detect a significant defect in DSB repair (DSBR) in primary fibroblasts from PNKP patients spanning the spectrum of PNKP-mutated pathologies. In contrast, the rate of SSB repair (SSBR) is markedly reduced. Moreover, we show that the restoration of SSBR in patient fibroblasts collectively requires both the DNA kinase and DNA phosphatase activities of PNKP, and the fork-head associated (FHA) domain that interacts with the SSBR protein, XRCC1. Notably, however, the two enzymatic activities of PNKP appear to affect different aspects of disease pathology, with reduced DNA phosphatase activity correlating with neurodevelopmental dysfunction and reduced DNA kinase activity correlating with neurodegeneration. In summary, these data implicate reduced rates of SSBR, not DSBR, as the source of both neurodevelopmental and neurodegenerative pathology in PNKP-mutated disease, and the extent and nature of this reduction as the primary determinant of disease severity.

• MeSH
• apraxie genetika   patologie   MeSH
• Charcotova-Marieova-Toothova nemoc genetika   patologie   MeSH
• dvouřetězcové zlomy DNA * MeSH
• enzymy opravy DNA genetika   MeSH
• fibroblasty metabolismus   patologie   MeSH
• fosfotransferasy s alkoholovou skupinou jako akceptorem genetika   MeSH
• jednořetězcové zlomy DNA * MeSH
• lidé MeSH
• mikrocefalie genetika   patologie   MeSH
• mutace genetika   MeSH
• oprava DNA genetika   MeSH
• protein XRCC1 genetika   MeSH
• záchvaty genetika   patologie   MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

Gene targeting is becoming an important tool for precision genome engineering in plants. During gene replacement, a variant of gene targeting, transformed DNA integrates into the genome by homologous recombination (HR) to replace resident sequences. We have analysed gene targeting in barley (Hordeum vulgare) using a model system based on double-strand break (DSB) induction by the meganuclease I-SceI and a transgenic, artificial target locus. In the plants we obtained, the donor construct was inserted at the target locus by homology-directed DNA integration in at least two transformants obtained in a single experiment and was stably inherited as a single Mendelian trait. Both events were produced by one-sided integration. Our data suggest that gene replacement can be achieved in barley with a frequency suitable for routine application. The use of a codon-optimized nuclease and co-transfer of the nuclease gene together with the donor construct are probably the components important for efficient gene targeting. Such an approach, employing the recently developed synthetic nucleases/nickases that allow DSB induction at almost any sequence of a genome of interest, sets the stage for precision genome engineering as a routine tool even for important crops such as barley.

• MeSH
• dvouřetězcové zlomy DNA * MeSH
• genetické lokusy MeSH
• geneticky modifikované rostliny MeSH
• genový targeting metody   MeSH
• ječmen (rod) genetika   MeSH
• kvantitativní polymerázová řetězová reakce MeSH
• modely genetické MeSH
• reprodukovatelnost výsledků MeSH
• rostlinné geny MeSH
• transformace genetická MeSH
• typy dědičnosti genetika   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

PURPOSE: The complex relationship between linear energy transfer (LET) and cellular response to radiation is not yet fully elucidated. To better characterize DNA damage after irradiations with therapeutic protons, we monitored formation and disappearance of DNA double-strand breaks (DNA DSB) as a function of LET and time. Comparisons with conventional γ-rays and high LET carbon ions were also performed. MATERIALS AND METHODS: In the present work, we performed immunofluorescence-based assay to determine the amount of DNA DSB induced by different LET values along the 62 MeV therapeutic proton Spread out Bragg peak (SOBP) in three cancer cell lines, i.e. HTB140 melanoma, MCF-7 breast adenocarcinoma and HTB177 non-small lung cancer cells. Time dependence of foci formation was followed as well. To determine irradiation positions, corresponding to the desired LET values, numerical simulations were carried out using Geant4 toolkit. We compared γ-H2AX foci persistence after irradiations with protons to that of γ-rays and carbon ions. RESULTS: With the rise of LET values along the therapeutic proton SOBP, the increase of γ-H2AX foci number is detected in the three cell lines up to the distal end of the SOBP, while there is a decrease on its distal fall-off part. With the prolonged incubation time, the number of foci gradually drops tending to attain the residual level. For the maximum number of DNA DSB, irradiation with protons attain higher level than that of γ-rays. Carbon ions produce more DNA DSB than protons but not substantially. The number of residual foci produced by γ-rays is significantly lower than that of protons and particularly carbon ions. Carbon ions do not produce considerably higher number of foci than protons, as it could be expected due to their physical properties. CONCLUSIONS: In situ visualization of γ-H2AX foci reveal creation of more lesions in the three cell lines by clinically relevant proton SOBP than γ-rays. The lack of significant differences in the number of γ-H2AX foci between the proton and carbon ion-irradiated samples suggests an increased complexity of DNA lesions and slower repair kinetics after carbon ions compared to protons. For all three irradiation types, there is no major difference between the three cell lines shortly after irradiations, while later on, the formation of residual foci starts to express the inherent nature of tested cells, therefore increasing discrepancy between them.

• MeSH
• dvouřetězcové zlomy DNA účinky záření   MeSH
• lidé MeSH
• lineární přenos energie * MeSH
• nádorové buněčné linie MeSH
• oprava DNA účinky záření   MeSH
• protony * MeSH
• relativní biologická účinnost MeSH
• viabilita buněk účinky záření   MeSH
• vztah dávky záření a odpovědi MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

Accumulation of repair proteins on damaged chromosomes is required to restore genomic integrity. However, the mechanisms of protein retention at the most destructive chromosomal lesions, the DNA double-strand breaks (DSBs), are poorly understood. We show that RNF8, a RING-finger ubiquitin ligase, rapidly assembles at DSBs via interaction of its FHA domain with the phosphorylated adaptor protein MDC1. This is accompanied by an increase in DSB-associated ubiquitylations and followed by accumulation of 53BP1 and BRCA1 repair proteins. Knockdown of RNF8 or disruption of its FHA or RING domains impaired DSB-associated ubiquitylation and inhibited retention of 53BP1 and BRCA1 at the DSB sites. In addition, we show that RNF8 can ubiquitylate histone H2A and H2AX, and that its depletion sensitizes cells to ionizing radiation. These data suggest that MDC1-mediated and RNF8-executed histone ubiquitylation protects genome integrity by licensing the DSB-flanking chromatin to concentrate repair factors near the DNA lesions.

• MeSH
• biologické modely MeSH
• chromatin metabolismus   MeSH
• DNA vazebné proteiny fyziologie   metabolismus   MeSH
• dvouřetězcové zlomy DNA * MeSH
• enzymy opravy DNA * metabolismus   MeSH
• fosforylace MeSH
• histony * metabolismus   MeSH
• intracelulární signální peptidy a proteiny metabolismus   MeSH
• jaderné proteiny metabolismus   MeSH
• lidé MeSH
• nádorové buňky kultivované MeSH
• protein BRCA1 metabolismus   MeSH
• terciární struktura proteinů MeSH
• trans-aktivátory metabolismus   MeSH
• ubikvitinace * MeSH
• vazba proteinů MeSH
• vazebná místa MeSH
• viabilita buněk MeSH
• Check Tag
• lidé MeSH

Reprogramming to pluripotency is associated with DNA damage and requires the functions of the BRCA1 tumor suppressor. Here, we leverage separation-of-function mutations in BRCA1/2 as well as the physical and/or genetic interactions between BRCA1 and its associated repair proteins to ascertain the relevance of homology-directed repair (HDR), stalled fork protection (SFP), and replication gap suppression (RGS) in somatic cell reprogramming. Surprisingly, loss of SFP and RGS is inconsequential for the transition to pluripotency. In contrast, cells deficient in HDR, but proficient in SFP and RGS, reprogram with reduced efficiency. Conversely, the restoration of HDR function through inactivation of 53bp1 rescues reprogramming in Brca1-deficient cells, and 53bp1 loss leads to elevated HDR and enhanced reprogramming in mouse and human cells. These results demonstrate that somatic cell reprogramming is especially dependent on repair of replication-associated double-strand breaks (DSBs) by the HDR activity of BRCA1 and BRCA2 and can be improved in the absence of 53BP1.

• MeSH
• 53BP1 * metabolismus   genetika   MeSH
• dvouřetězcové zlomy DNA * MeSH
• lidé MeSH
• myši MeSH
• oprava DNA * MeSH
• přeprogramování buněk * MeSH
• protein BRCA1 * metabolismus   genetika   MeSH
• rekombinační oprava DNA MeSH
• replikace DNA MeSH
• zvířata MeSH
• Check Tag
• lidé MeSH
• myši MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Research Support, N.I.H., Extramural MeSH

PR domain containing 9 (Prdm9) is specifying hotspots of meiotic recombination but in hybrids between two mouse subspecies Prdm9 controls failure of meiotic chromosome synapsis and hybrid male sterility. We have previously reported that Prdm9-controlled asynapsis and meiotic arrest are conditioned by the inter-subspecific heterozygosity of the hybrid genome and we presumed that the insufficient number of properly repaired PRDM9-dependent DNA double-strand breaks (DSBs) causes asynapsis of chromosomes and meiotic arrest (Gregorova et al., 2018). We now extend the evidence for the lack of properly processed DSBs by improving meiotic chromosome synapsis with exogenous DSBs. A single injection of chemotherapeutic drug cisplatin increased frequency of RPA and DMC1 foci at the zygotene stage of sterile hybrids, enhanced homolog recognition and increased the proportion of spermatocytes with fully synapsed homologs at pachytene. The results bring a new evidence for a DSB-dependent mechanism of synapsis failure and infertility of intersubspecific hybrids.

• MeSH
• cisplatina toxicita   MeSH
• dvouřetězcové zlomy DNA účinky léků   MeSH
• histonlysin-N-methyltransferasa genetika   metabolismus   MeSH
• hybridizace genetická MeSH
• meióza účinky léků   genetika   MeSH
• mužská infertilita genetika   MeSH
• myši inbrední C57BL MeSH
• oprava DNA MeSH
• párování chromozomů účinky léků   genetika   MeSH
• protinádorové látky toxicita   MeSH
• zvířata MeSH
• Check Tag
• mužské pohlaví MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

Double-strand breaks (DSBs), continuously introduced into DNA by cell metabolism, ionizing radiation and some chemicals, are the biologically most deleterious type of genome damage, and must be accurately repaired to protect genomic integrity, ensure cell survival, and prevent carcinogenesis. Although a huge amount of information has been published on the molecular basis and biological significance of DSB repair, our understanding of DSB repair and its spatiotemporal arrangement is still incomplete. In particular, the role of higher-order chromatin structure in DSB induction and repair, movement of DSBs and the mechanism giving rise to chromatin exchanges, and many other currently disputed questions are discussed in this review. Finally, a model explaining the formation of chromosome translocations is proposed.

• MeSH
• biologické modely MeSH
• chromatin účinky záření   ultrastruktura   MeSH
• dvouřetězcové zlomy DNA MeSH
• ionizující záření MeSH
• lidé MeSH
• oprava DNA MeSH
• poškození DNA MeSH
• translokace genetická MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• přehledy MeSH

DNA double-strand breaks (DSBs) represent a lethal form of DNA damage that can trigger cell death or initiate oncogenesis. The activity of RNA polymerase II (RNAPII) at the break site is required for efficient DSB repair. However, the regulatory mechanisms governing the transcription cycle at DSBs are not well understood. Here, we show that Integrator complex subunit 6 (INTS6) associates with the heterotrimeric sensor of ssDNA (SOSS1) complex (comprising INTS3, INIP and hSSB1) to form the tetrameric SOSS1 complex. INTS6 binds to DNA:RNA hybrids and promotes Protein Phosphatase 2A (PP2A) recruitment to DSBs, facilitating the dephosphorylation of RNAPII. Furthermore, INTS6 prevents the accumulation of damage-associated RNA transcripts (DARTs) and the stabilization of DNA:RNA hybrids at DSB sites. INTS6 interacts with and promotes the recruitment of senataxin (SETX) to DSBs, facilitating the resolution of DNA:RNA hybrids/R-loops. Our results underscore the significance of the tetrameric SOSS1 complex in the autoregulation of DNA:RNA hybrids and efficient DNA repair.

• MeSH
• DNA vazebné proteiny metabolismus   MeSH
• DNA-helikasy metabolismus   genetika   MeSH
• DNA * metabolismus   chemie   MeSH
• dvouřetězcové zlomy DNA * MeSH
• fosforylace MeSH
• homeostáza genetika   MeSH
• lidé MeSH
• oprava DNA * MeSH
• proteinfosfatasa 2 metabolismus   genetika   MeSH
• R-smyčka MeSH
• RNA-helikasy metabolismus   genetika   MeSH
• RNA-polymerasa II * metabolismus   MeSH
• RNA * metabolismus   genetika   chemie   MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH

In male germ cells the repair of DNA double strand breaks (DSBs) differs from that described for somatic cell lines. Irradiation induced immunofluorescent foci (IRIF's) signifying a double strand DNA breaks, were followed in spermatogenic cells up to 16 h after the insult. Foci were characterised for Mdc1, 53BP1 and Rad51 that always were expressed in conjecture with gamma-H2AX. Subsequent spermatogenic cell types were found to have different repair proteins. In early germ cells up to the start of meiotic prophase, i.e. in spermatogonia and preleptotene spermatocytes, 53BP1 and Rad51 are available but no Mdc1 is expressed in these cells before and after irradiation. The latter might explain the radiosensitivity of spermatogonia. Spermatocytes from shortly after premeiotic S-phase till pachytene in epithelial stage IV/V express Mdc1 and Rad51 but no 53BP1 which has no role in recombination involved repair during the early meiotic prophase. Mdc1 is required during this period as in Mdc1 deficient mice all spermatocytes enter apoptosis in epithelial stage IV when they should start mid-pachytene phase of the meiotic prophase. From stage IV mid pachytene spermatocytes to round spermatids, Mdc1 and 53BP1 are expressed while Rad51 is no longer expressed in the haploid round spermatids. Quantifying foci numbers of gamma-H2AX, Mdc1 and 53BP1 at various time points after irradiation revealed a 70% reduction after 16 h in pachytene and diplotene spermatocytes and round spermatids. Although the DSB repair efficiency is higher then in spermatogonia where only a 40% reduction was found, it still does not compare to somatic cell lines where a 70% reduction occurs in 2 h. Taken together, DNA DSBs repair proteins differ for the various types of spermatogenic cells, no germ cell type possessing the complete set. This likely leads to a compromised efficiency relative to somatic cell lines. From the evolutionary point of view it may be an advantage when germ cells die from DNA damage rather than risk the acquisition of transmittable errors made during the repair process.

• MeSH
• chromozomální proteiny, nehistonové MeSH
• DNA vazebné proteiny MeSH
• DNA * účinky záření   MeSH
• dvouřetězcové zlomy DNA * MeSH
• fluorescenční protilátková technika MeSH
• fosfoproteiny * metabolismus   MeSH
• histony metabolismus   MeSH
• inbrední kmeny myší MeSH
• intracelulární signální peptidy a proteiny fyziologie   genetika   metabolismus   MeSH
• meióza fyziologie   MeSH
• myši knockoutované MeSH
• myši MeSH
• oprava DNA * MeSH
• rekombinasa Rad51 metabolismus   MeSH
• rentgenové záření MeSH
• spermatocyty * účinky záření   MeSH
• spermatogonie metabolismus   MeSH
• vztah dávky záření a odpovědi MeSH
• zárodečné buňky metabolismus   účinky záření   MeSH
• zvířata MeSH
• Check Tag
• mužské pohlaví MeSH
• myši MeSH
• zvířata MeSH