A long-duration gamma-ray burst with a peculiar origin.

It is generally believed that long-duration gamma-ray bursts (GRBs) are associated with massive star core collapse1, whereas short-duration GRBs are associated with mergers of compact star binaries2. However, growing observations3-6 have suggested that oddball GRBs do exist, and several criteria (prompt emission properties, supernova/kilonova associations and host galaxy properties) rather than burst duration only are needed to classify GRBs physically7. A previously reported long-duration burst, GRB 060614 (ref. 3), could be viewed as a short GRB with extended emission if it were observed at a larger distance8 and was associated with a kilonova-like feature9. As a result, it belongs to the type I (compact star merger) GRB category and is probably of binary neutron star (NS) merger origin. Here we report a peculiar long-duration burst, GRB 211211A, whose prompt emission properties in many aspects differ from all known type I GRBs, yet its multiband observations suggest a non-massive-star origin. In particular, substantial excess emission in both optical and near-infrared wavelengths has been discovered (see also ref. 10), which resembles kilonova emission, as observed in some type I GRBs. These observations point towards a new progenitor type of GRBs. A scenario invoking a white dwarf (WD)-NS merger with a post-merger magnetar engine provides a self-consistent interpretation for all the observations, including prompt gamma rays, early X-ray afterglow, as well as the engine-fed11,12 kilonova emission.

PD-L1 (B7-H1) Competes with the RNA Exosome to Regulate the DNA Damage Response and Can Be Targeted to Sensitize to Radiation or Chemotherapy.

Programmed death ligand 1 (PD-L1, also called B7-H1) is an immune checkpoint protein that inhibits immune function through its binding of the programmed cell death protein 1 (PD-1) receptor. Clinically approved antibodies block extracellular PD-1 and PD-L1 binding, yet the role of intracellular PD-L1 in cancer remains poorly understood. Here, we discovered that intracellular PD-L1 acts as an RNA binding protein that regulates the mRNA stability of NBS1, BRCA1, and other DNA damage-related genes. Through competition with the RNA exosome, intracellular PD-L1 protects targeted RNAs from degradation, thereby increasing cellular resistance to DNA damage. RNA immunoprecipitation and RNA-seq experiments demonstrated that PD-L1 regulates RNA stability genome-wide. Furthermore, we developed a PD-L1 antibody, H1A, which abrogates the interaction of PD-L1 with CMTM6, thereby promoting PD-L1 degradation. Intracellular PD-L1 may be a potential therapeutic target to enhance the efficacy of radiotherapy and chemotherapy in cancer through the inhibition of DNA damage response and repair.

DNA damage in oocytes induces a switch of the quality control factor TAp63α from dimer to tetramer.

TAp63α, a homolog of the p53 tumor suppressor, is a quality control factor in the female germline. Remarkably, already undamaged oocytes express high levels of the protein, suggesting that TAp63α's activity is under tight control of an inhibitory mechanism. Biochemical studies have proposed that inhibition requires the C-terminal transactivation inhibitory domain. However, the structural mechanism of TAp63α inhibition remains unknown. Here, we show that TAp63α is kept in an inactive dimeric state. We reveal that relief of inhibition leads to tetramer formation with ∼20-fold higher DNA affinity. In vivo, phosphorylation-triggered tetramerization of TAp63α is not reversible by dephosphorylation. Furthermore, we show that a helix in the oligomerization domain of p63 is crucial for tetramer stabilization and competes with the transactivation domain for the same binding site. Our results demonstrate how TAp63α is inhibited by complex domain-domain interactions that provide the basis for regulating quality control in oocytes.

Fluctuations in p53 Signaling Allow Escape from Cell-Cycle Arrest.

Biological signals need to be robust and filter small fluctuations yet maintain sensitivity to signals across a wide range of magnitudes. Here, we studied how fluctuations in DNA damage signaling relate to maintenance of long-term cell-cycle arrest. Using live-cell imaging, we quantified division profiles of individual human cells in the course of 1 week after irradiation. We found a subset of cells that initially establish cell-cycle arrest and then sporadically escape and divide. Using fluorescent reporters and mathematical modeling, we determined that fluctuations in the oscillatory pattern of the tumor suppressor p53 trigger a sharp switch between p21 and CDK2, leading to escape from arrest. Transient perturbation of p53 stability mimicked the noise in individual cells and was sufficient to trigger escape from arrest. Our results show that the self-reinforcing circuitry that mediates cell-cycle transitions can translate small fluctuations in p53 signaling into large phenotypic changes.

Surge of neurophysiological coupling and connectivity of gamma oscillations in the dying human brain.

The brain is assumed to be hypoactive during cardiac arrest. However, animal models of cardiac and respiratory arrest demonstrate a surge of gamma oscillations and functional connectivity. To investigate whether these preclinical findings translate to humans, we analyzed electroencephalogram and electrocardiogram signals in four comatose dying patients before and after the withdrawal of ventilatory support. Two of the four patients exhibited a rapid and marked surge of gamma power, surge of cross-frequency coupling of gamma waves with slower oscillations, and increased interhemispheric functional and directed connectivity in gamma bands. High-frequency oscillations paralleled the activation of beta/gamma cross-frequency coupling within the somatosensory cortices. Importantly, both patients displayed surges of functional and directed connectivity at multiple frequency bands within the posterior cortical "hot zone," a region postulated to be critical for conscious processing. This gamma activity was stimulated by global hypoxia and surged further as cardiac conditions deteriorated in the dying patients. These data demonstrate that the surge of gamma power and connectivity observed in animal models of cardiac arrest can be observed in select patients during the process of dying.

Dynamic switching of neural oscillations in the prefrontal-amygdala circuit for naturalistic freeze-or-flight.

The medial prefrontal cortex (mPFC) and basolateral amygdala (BLA) are involved in the regulation of defensive behavior under threat, but their engagement in flexible behavior shifts remains unclear. Here, we report the oscillatory activities of mPFC-BLA circuit in reaction to a naturalistic threat, created by a predatory robot in mice. Specifically, we found dynamic frequency tuning among two different theta rhythms (~5 or ~10 Hz) was accompanied by agile changes of two different defensive behaviors (freeze-or-flight). By analyzing flight trajectories, we also found that high beta (~30 Hz) is engaged in the top-down process for goal-directed flights and accompanied by a reduction in fast gamma (60 to 120 Hz, peak near 70 Hz). The elevated beta nested the fast gamma activity by its phase more strongly. Our results suggest that the mPFC-BLA circuit has a potential role in oscillatory gear shifting allowing flexible information routing for behavior switches.

BCL-XL exerts a protective role against anemia caused by radiation-induced kidney damage.

Studies of gene-targeted mice identified the roles of the different pro-survival BCL-2 proteins during embryogenesis. However, little is known about the role(s) of these proteins in adults in response to cytotoxic stresses, such as treatment with anti-cancer agents. We investigated the role of BCL-XL in adult mice using a strategy where prior bone marrow transplantation allowed for loss of BCL-XL exclusively in non-hematopoietic tissues to prevent anemia caused by BCL-XL deficiency in erythroid cells. Unexpectedly, the combination of total body γ-irradiation (TBI) and genetic loss of Bcl-x caused secondary anemia resulting from chronic renal failure due to apoptosis of renal tubular epithelium with secondary obstructive nephropathy. These findings identify a critical protective role of BCL-XL in the adult kidney and inform on the use of BCL-XL inhibitors in combination with DNA damage-inducing drugs for cancer therapy. Encouragingly, the combination of DNA damage-inducing anti-cancer therapy plus a BCL-XL inhibitor could be tolerated in mice, at least when applied sequentially.

Role of Yrn2 under oxidative stress in Deinococcus radiodurans.

Among the two Y RNAs in Deinococcus radiodurans, the functional properties of Yrn2 are still not known. Yrn2 although consists of a long stem-loop for Rsr binding, differs from Yrn1 in the effector binding site. An initial study on Yrn2 delineated it to be a UV-induced noncoding RNA. Apart from that Yrn2 has scarcely been investigated. In the current study, we identified Yrn2 as an γ-radiation induced Y RNA, which is also induced upon H2O2 and mitomycin treatment. Ectopically expressed Yrn2 appeared to be nontoxic to the cell growth. An overabundance of Yrn2 was found to ameliorate cell survival under oxidative stress through the detoxification of intracellular reactive oxygen species with a subsequent decrease in total protein carbonylation. A significant accumulation of intracellular Mn(II) with unaltered Fe(II) and Zn(II) with detected while Yrn2 is overabundant in the cells. This study identified the role of a novel Yrn2 under oxidative stress in D. radiodurans.

Analysis method of cellular stress caused by intermediate dose-rate irradiation using a cell lysate array technique.

Ionizing radiation damages DNA and may lead to the development of cancer. Irradiation also generates reactive oxygen species (ROS) which cause damage to various biological molecules. Relatively low dose-rate irradiation causes less damage. However, the damage and its effects on cell fate are difficult to evaluate. To develop a method to analyze the damage and accompanying changes in physiology in cells irradiated by γ-rays at a relatively low dose-rate, we used the protein array technique to quantify marker proteins involved in the stress response and the regulation of cell growth and death. This method enabled efficient analyses of many replicates of experimental data on cell lysate samples. We detected relatively small changes in the levels of these proteins in the irradiated cells. Changes in protein levels suggested ROS production and DNA damage as well as cell cycle retardation and the progression of cellular senescence. Thus, our approach shows promise for analyzing the biological effects of relatively low dose-rate irradiation.

A novel ionizing radiation-induced small RNA, DrsS, promotes the detoxification of reactive oxygen species in Deinococcus radiodurans.

A plethora of gene regulatory mechanisms with eccentric attributes in Deinoccocus radiodurans confer it to possess a distinctive ability to survive under ionizing radiation. Among the many regulatory processes, small RNA (sRNA)-mediated regulation of gene expression is prevalent in bacteria but barely investigated in D. radiodurans. In the current study, we identified a novel sRNA, DrsS, through RNA-seq analysis in D. radiodurans cells while exposed to ionizing radiation. Initial sequence analysis for promoter identification revealed that drsS is potentially co-transcribed with sodA and dr_1280 from a single operon. Elimination of the drsS allele in D. radiodurans chromosome resulted in an impaired growth phenotype under γ-radiation. DrsS has also been found to be upregulated under oxidative and genotoxic stresses. Deletion of the drsS gene resulted in the depletion of intracellular concentration of both Mn2+ and Fe2+ by ~70% and 40%, respectively, with a concomitant increase in carbonylation of intracellular protein. Complementation of drsS gene in ΔdrsS cells helped revert its intracellular Mn2+ and Fe2+ concentration and alleviated carbonylation of intracellular proteins. Cells with deleted drsS gene exhibited higher sensitivity to oxidative stress than wild-type cells. Extrachromosomally expressed drsS in ΔdrsS cells retrieved its oxidative stress resistance properties by catalase-mediated detoxification of reactive oxygen species (ROS). In vitro binding assays indicated that DsrS directly interacts with the coding region of the katA transcript, thus possibly protecting it from cellular endonucleases in vivo. This study identified a novel small RNA DrsS and investigated its function under oxidative stress in D. radiodurans. IMPORTANCE: Deinococcus radiodurans possesses an idiosyncratic quality to survive under extreme ionizing radiation and, thus, has evolved with diverse mechanisms which promote the mending of intracellular damages caused by ionizing radiation. As sRNAs play a pivotal role in modulating gene expression to adapt to altered conditions and have been delineated to participate in almost all physiological processes, understanding the regulatory mechanism of sRNAs will unearth many pathways that lead to radioresistance in D. radiodurans. In that direction, DrsS has been identified to be a γ-radiation-induced sRNA, which is also induced by oxidative and genotoxic stresses. DrsS appeared to activate catalase under oxidative stress and detoxify intracellular ROS. This sRNA has also been shown to balance intracellular Mn(II) and Fe concentrations protecting intracellular proteins from carbonylation. This novel mechanism of DrsS identified in D. radiodurans adds substantially to our knowledge of how this bacterium exploits sRNA for its survival under stresses.

Monocytes-macrophages that express α-smooth muscle actin preserve primitive hematopoietic cells in the bone marrow.

Hematopoietic stem and progenitor cells (HSPCs) are regulated by various bone marrow stromal cell types. Here we identified rare activated bone marrow monocytes and macrophages with high expression of α-smooth muscle actin (α-SMA) and the cyclooxygenase COX-2 that were adjacent to primitive HSPCs. These myeloid cells resisted radiation-induced cell death and further upregulated COX-2 expression under stress conditions. COX-2-derived prostaglandin E(2) (PGE(2)) prevented HSPC exhaustion by limiting the production of reactive oxygen species (ROS) via inhibition of the kinase Akt and higher stromal-cell expression of the chemokine CXCL12, which is essential for stem-cell quiescence. Our study identifies a previously unknown subset of α-SMA(+) activated monocytes and macrophages that maintain HSPCs and protect them from exhaustion during alarm situations.

Complement is a central mediator of radiotherapy-induced tumor-specific immunity and clinical response.

Radiotherapy induces DNA damage and cell death, but recent data suggest that concomitant immune stimulation is an integral part of the therapeutic action of ionizing radiation. It is poorly understood how radiotherapy supports tumor-specific immunity. Here we report that radiotherapy induced tumor cell death and transiently activated complement both in murine and human tumors. The local production of pro-inflammatory anaphylatoxins C3a and C5a was crucial to the tumor response to radiotherapy and concomitant stimulation of tumor-specific immunity. Dexamethasone, a drug frequently given during radiotherapy, limited complement activation and the anti-tumor effects of the immune system. Overall, our findings indicate that anaphylatoxins are key players in radiotherapy-induced tumor-specific immunity and the ensuing clinical responses.

Islatravir Dimer: Crystal Form Dependence of a Radiation-Induced Degradation Product.

A rare example of crystal form-dependent, gamma radiation-induced degradation is presented. Islatravir is known to exist in several polymorphic forms, but only one of these forms shows the generation of a specific dimer degradation product under gamma irradiation. Extended gamma irradiation studies demonstrated that only one of the known crystalline forms shows an appreciable rate of dimer formation. Additionally, this dimer is not observed to form under other forced stress conditions. We present the structural elucidation of this dimer impurity and rationalize its form-dependent generation based on the analysis of the underlying crystal structure.

X-ray irradiation effectively inactivated lymphocytes in transfusion in vivo monitored by the bioluminescence transfusion-associated graft-versus-host disease model.

BACKGROUND AND OBJECTIVES: Transfusion of cold-stored whole blood is the preferred resuscitation method for trauma patients but may cause transfusion-associated graft-versus-host disease (TA-GVHD). Standard clinical practice to prevent this is to irradiate blood components with gamma-rays. X-ray irradiations are also a safe and effective alternative to gamma-ray irradiation. We established a visual mouse model of TA-GVHD to compare the viability and function of lymphocytes exposed to gamma- and x-ray irradiation. MATERIALS AND METHODS: A haploidentical transplantation mouse model was established to simulate TA-GVHD with Balb/c mice as donors and hybrid F1 CB6 mice (Balb/c × C57) as recipients. Spleen cells from Tg-Fluc+ Balb/c mice were isolated and irradiated with gamma-rays and x-rays. Lymphocyte activation, apoptosis and proliferation post phorbol 1 2-myristate 1 3-acetate (PMA) stimulation were evaluated. After transfusion, we monitored Fluc+ lymphocytes daily by bioluminescence imaging. Recipients were euthanized on day 21, and tissues were examined pathologically and for inflammatory cytokines. RESULTS: The viability of gamma- or x-ray irradiated lymphocytes decreased significantly with slight changes in proliferation in vivo after transfusion. Compared with the non-irradiated group, both the gamma- and x-ray irradiated groups showed significantly decreased clinical scoring and inflammatory cytokine levels. The fluorescence intensity of the body and target organs was reduced after irradiation. CONCLUSION: No recipients acquired TA-GVHD after lymphocyte transfusion subjected to gamma- or x-rays, showing that x-rays inactivate as well as gamma rays and are suitable for irradiating whole blood.

Production and characterization of melanin pigment from black fungus Curvularia soli AS21 ON076460 assisted gamma rays for promising medical uses.

Owing to the growing need for natural materials in different fields, studying melanin production from biological sources is imperative. In the current study, the extracellular melanin pigment was produced by the fungus Curvularia soli AS21 ON076460. The factors that affect the production of melanin were optimized by the Plackett-Burman design (P-BD). The effect of gamma irradiation on melanin productivity was investigated. The maximum melanin yield (3.376 mg/L) was elicited by a stimulus of gamma irradiation at 1.0 kGy. The results evoked that, Curvularia soli AS21 ON076460 melanin exhibited excellent antimicrobial activity against all tested bacteria and fungi. Klebsiella pneumoniae ATCC 13883 and P. digitatum were mostly affected by melanin registering the inhibition zone diameters of 37.51 ± 0.012 and 44.25 ± 0.214 mm, respectively. Moreover, Curvularia soli AS21 ON076460 melanin indicated a significant antiviral efficacy (77% inhibition) of Herpes simplex virus (HSV1). The melanin pigment showed antioxidant activities with IC50 of 42 ± 0.021 and 17 ± 0.02 µg/mL against DPPH and NO, respectively. Melanin had cytotoxic action against human breast cancer and skin cancer cell lines (Mcf7and A431) as well as exerting a low percentage of cell death against normal skin cell lines (Hfb4). Melanin was effective in wound management of human skin cells by 63.04 ± 1.83% compared with control (68.67 ± 1.10%). The novelty in the study is attributed to the possibility of using gamma rays as a safe method in small economic doses to stimulate melanin production from the fungi that have been isolated. In summary, melanin produced from fungi has significant biological activities that encourage its usage as a supportive medical route.

Local Community Assembly Mechanisms and the Size of Species Pool Jointly Explain the Beta Diversity of Soil Fungi.

Fungi play vital regulatory roles in terrestrial ecosystems. Local community assembly mechanisms, including deterministic and stochastic processes, as well as the size of regional species pools (gamma diversity), typically influence overall soil microbial community beta diversity patterns. However, there is limited evidence supporting their direct and indirect effects on beta diversity of different soil fungal functional groups in forest ecosystems. To address this gap, we collected 1606 soil samples from a 25-ha subtropical forest plot in southern China. Our goal was to determine the direct effects and indirect effects of regional species pools on the beta diversity of soil fungi, specifically arbuscular mycorrhizal (AM), ectomycorrhizal (EcM), plant-pathogenic, and saprotrophic fungi. We quantified the effects of soil properties, mycorrhizal tree abundances, and topographical factors on soil fungal diversity. The beta diversity of plant-pathogenic fungi was predominantly influenced by the size of the species pool. In contrast, the beta diversity of EcM fungi was primarily driven indirectly through community assembly processes. Neither of them had significant effects on the beta diversity of AM and saprotrophic fungi. Our results highlight that the direct and indirect effects of species pools on the beta diversity of soil functional groups of fungi can significantly differ even within a relatively small area. They also demonstrate the independent and combined effects of various factors in regulating the diversities of soil functional groups of fungi. Consequently, it is crucial to study the fungal community not only as a whole but also by considering different functional groups within the community.

Dynamics of Chromosome Aberrations and Cell Death in Zebrafish Embryos Exposed to 137Cs Total-Body Irradiation.

Ionizing radiation exposure induces significant DNA damage and cell death in aquatic species. Accurate sensing and quantification play pivotal roles in environmental monitoring and surveillance. Zebrafish (Danio rerio) is a well-suited animal model for research into this aspect, especially with recent development of cytogenetic and transgenic tools. In this study, we present time-course studies of chromosome aberrations and cell death in zebrafish embryos exposed to 2 Gy 137Cs total-body irradiation. Using a cytogenetic approach, we quantified chromosome and chromatid aberrations in irradiated embryos at 6, 14, 20, and 24 h postirradiation. Metaphases with aberrations showed rapid declining kinetics, accompanied by incomplete karyotypes and irregular chromatin contents. Using an apoptosis-reporting transgenic zebrafish, we found increasing cell death along these time points, with the embryonic eyes and brain contributing the majority of the cell death volumes. We provide evidence that self-proliferating progenitor cells form the underlying linkage between the two kinetics and their positions define radiosensitive niches in zebrafish embryos. Our results provide detailed chromosome aberration and cell death dynamics in 137Cs-irradiated zebrafish embryos and unveil the appropriate timeline and tissue positions for accurate sensing and quantification of radiation-induced damages in zebrafish embryos.

DNA-PKcs-PIDDosome: a nuclear caspase-2-activating complex with role in G2/M checkpoint maintenance.

Caspase-2 is unique among all the mammalian caspases in that it is the only caspase that is present constitutively in the cell nucleus, in addition to other cellular compartments. However, the functional significance of this nuclear localization is unknown. Here we show that DNA damage induced by gamma-radiation triggers the phosphorylation of nuclear caspase-2 at the S122 site within its prodomain, leading to its cleavage and activation. This phosphorylation is carried out by the nuclear serine/threonine protein kinase DNA-PKcs and promoted by the p53-inducible death-domain-containing protein PIDD within a large nuclear protein complex consisting of DNA-PKcs, PIDD, and caspase-2, which we have named the DNA-PKcs-PIDDosome. This phosphorylation and the catalytic activity of caspase-2 are involved in the maintenance of a G2/M DNA damage checkpoint and DNA repair mediated by the nonhomologous end-joining (NHEJ) pathway. The DNA-PKcs-PIDDosome thus represents a protein complex that impacts mammalian G2/M DNA damage checkpoint and NHEJ.

Recombination and replication in DNA repair of heavily irradiated Deinococcus radiodurans.

Deinococcus radiodurans' extreme resistance to ionizing radiation, desiccation, and DNA-damaging chemicals involves a robust DNA repair that reassembles its shattered genome. The repair process requires diploidy and commences with an extensive exonucleolytic erosion of DNA fragments. Liberated single-stranded overhangs prime strand elongation on overlapping fragments and the elongated complementary strands reestablish chromosomal contiguity by annealing. We explored the interdependence of the DNA recombination and replication processes in the reconstitution of the D. radiodurans genome disintegrated by ionizing radiation. The priming of extensive DNA repair synthesis involves RecA and RadA proteins. DNA polymerase III is essential for the initiation of repair synthesis, whereas efficient elongation requires DNA polymerases I and III. Inactivation of both polymerases leads to degradation of DNA fragments and rapid cell death. The present in vivo characterization of key recombination and replication processes dissects the mechanism of DNA repair in heavily irradiated D. radiodurans.

53BP1 Integrates DNA Repair and p53-Dependent Cell Fate Decisions via Distinct Mechanisms.

The tumor suppressor protein 53BP1, a pivotal regulator of DNA double-strand break (DSB) repair, was first identified as a p53-interacting protein over two decades ago. However, its direct contributions to p53-dependent cellular activities remain undefined. Here, we reveal that 53BP1 stimulates genome-wide p53-dependent gene transactivation and repression events in response to ionizing radiation (IR) and synthetic p53 activation. 53BP1-dependent p53 modulation requires both auto-oligomerization and tandem-BRCT domain-mediated bivalent interactions with p53 and the ubiquitin-specific protease USP28. Loss of these activities results in inefficient p53-dependent cell-cycle checkpoint and exit responses. Furthermore, we demonstrate 53BP1-USP28 cooperation to be essential for normal p53-promoter element interactions and gene transactivation-associated events, yet dispensable for 53BP1-dependent DSB repair regulation. Collectively, our data provide a mechanistic explanation for 53BP1-p53 cooperation in controlling anti-tumorigenic cell-fate decisions and reveal these activities to be distinct and separable from 53BP1's regulation of DNA double-strand break repair pathway choice.