Structural insight into BRCA1-BARD1 complex recruitment to damaged chromatin.

The BRCA1-BARD1 complex directs the DNA double-strand break (DSB) repair pathway choice to error-free homologous recombination (HR) during the S-G2 stages. Targeting BRCA1-BARD1 to DSB-proximal sites requires BARD1-mediated nucleosome interaction and histone mark recognition. Here, we report the cryo-EM structure of BARD1 bound to a ubiquitinated nucleosome core particle (NCPUb) at 3.1 Å resolution and illustrate how BARD1 simultaneously recognizes the DNA damage-induced mark H2AK15ub and DNA replication-associated mark H4K20me0 on the nucleosome. In vitro and in vivo analyses reveal that the BARD1-NCPUb complex is stabilized by BARD1-nucleosome interaction, BARD1-ubiquitin interaction, and BARD1 ARD domain-BARD1 BRCT domain interaction, and abrogating these interactions is detrimental to HR activity. We further identify multiple disease-causing BARD1 mutations that disrupt BARD1-NCPUb interactions and hence impair HR. Together, this study elucidates the mechanism of BRCA1-BARD1 complex recruitment and retention by DSB-flanking nucleosomes and sheds important light on cancer therapeutic avenues.

The ZATT-TOP2A-PICH Axis Drives Extensive Replication Fork Reversal to Promote Genome Stability.

Replication fork reversal is a global response to replication stress in mammalian cells, but precisely how it occurs remains poorly understood. Here, we show that, upon replication stress, DNA topoisomerase IIalpha (TOP2A) is recruited to stalled forks in a manner dependent on the SNF2-family DNA translocases HLTF, ZRANB3, and SMARCAL1. This is accompanied by an increase in TOP2A SUMOylation mediated by the SUMO E3 ligase ZATT and followed by recruitment of a SUMO-targeted DNA translocase, PICH. Disruption of the ZATT-TOP2A-PICH axis results in accumulation of partially reversed forks and enhanced genome instability. These results suggest that fork reversal occurs via a sequential two-step process. First, HLTF, ZRANB3, and SMARCAL1 initiate limited fork reversal, creating superhelical strain in the newly replicated sister chromatids. Second, TOP2A drives extensive fork reversal by resolving the resulting topological barriers and via its role in recruiting PICH to stalled forks.

UFL1 triggers replication fork degradation by MRE11 in BRCA1/2-deficient cells.

The stabilization of stalled forks has emerged as a crucial mechanism driving resistance to poly(ADP-ribose) polymerase (PARP) inhibitors in BRCA1/2-deficient tumors. Here, we identify UFL1, a UFM1-specific E3 ligase, as a pivotal regulator of fork stability and the response to PARP inhibitors in BRCA1/2-deficient cells. On replication stress, UFL1 localizes to stalled forks and catalyzes the UFMylation of PTIP, a component of the MLL3/4 methyltransferase complex, specifically at lysine 148. This modification facilitates the assembly of the PTIP-MLL3/4 complex, resulting in the enrichment of H3K4me1 and H3K4me3 at stalled forks and subsequent recruitment of the MRE11 nuclease. Consequently, loss of UFL1, disruption of PTIP UFMylation or overexpression of the UFM1 protease UFSP2 protects nascent DNA strands from extensive degradation and confers resistance to PARP inhibitors in BRCA1/2-deficient cells. These findings provide mechanistic insights into the processes underlying fork instability in BRCA1/2-deficient cells and offer potential therapeutic avenues for the treatment of BRCA1/2-deficient tumors.

RNF4 controls the extent of replication fork reversal to preserve genome stability.

Replication fork reversal occurs via a two-step process that entails reversal initiation and reversal extension. DNA topoisomerase IIalpha (TOP2A) facilitates extensive fork reversal, on one hand through resolving the topological stress generated by the initial reversal, on the other hand via its role in recruiting the SUMO-targeted DNA translocase PICH to stalled forks in a manner that is dependent on its SUMOylation by the SUMO E3 ligase ZATT. However, how TOP2A activities at stalled forks are precisely regulated remains poorly understood. Here we show that, upon replication stress, the SUMO-targeted ubiquitin E3 ligase RNF4 accumulates at stalled forks and targets SUMOylated TOP2A for ubiquitination and degradation. Downregulation of RNF4 resulted in aberrant activation of the ZATT-TOP2A-PICH complex at stalled forks, which in turn led to excessive reversal and elevated frequencies of fork collapse. These results uncover a previously unidentified regulatory mechanism that regulates TOP2A activities at stalled forks and thus the extent of fork reversal.

ATM controls the extent of DNA end resection by eliciting sequential posttranslational modifications of CtIP.

DNA end resection is a critical step in the repair of DNA double-strand breaks (DSBs) via homologous recombination (HR). However, the mechanisms governing the extent of resection at DSB sites undergoing homology-directed repair remain unclear. Here, we show that, upon DSB induction, the key resection factor CtIP is modified by the ubiquitin-like protein SUMO at lysine 578 in a PIAS4-dependent manner. CtIP SUMOylation occurs on damaged chromatin and requires prior hyperphosphorylation by the ATM protein kinase. SUMO-modified hyperphosphorylated CtIP is targeted by the SUMO-dependent E3 ubiquitin ligase RNF4 for polyubiquitination and subsequent degradation. Consequently, disruption of CtIP SUMOylation results in aberrant accumulation of CtIP at DSBs, which, in turn, causes uncontrolled excessive resection, defective HR, and increased cellular sensitivity to DSB-inducing agents. These findings reveal a previously unidentified regulatory mechanism that regulates CtIP activity at DSBs and thus the extent of end resection via ATM-dependent sequential posttranslational modification of CtIP.

Study on the treatment of advanced lung adenocarcinoma in the elderly with pemetrexed combined with platinum drugs.

To study the treatment of advanced lung adenocarcinoma in the elderly with pemetrexed combined with platinum drugs. 200 elderly patients who had been treated for advanced lung adenocarcinoma in our hospital were enrolled as research objects. They were randomly divided into control group and research group, each containing 100 patients. The control group was given Pemetrexed therapy and routine nursing mode, while the research group was given pemetrexed combined with platinum drugs and evidence-based nursing mode. The therapeutic effect and nursing effect of the two groups were compared. The overall treatment effective rate of the research was 85.00% and that of the control group was 60.00%, indicating the research group had significant advantage over the control group, p<0.05. The incidence of adverse reactions including nausea, vomiting, constipation, diarrhea, bone marrow suppression, fatigue and fatigue, and hair loss was significantly lower in the research group (22.00%) than that in the control group (45.00%), p<0.05. The quality of life of the research group was higher than that of the control group, p<0.05. For the elderly patients with advanced lung adenocarcinoma, the implementation of pemetrexed combined with platinum drug can help patients get better treatment results.

Clinical effect of cervical paravertebral nerve block combined with Mailuoning and Angelica sinensis in treatment of nerve-root type cervical spondylosis.

To observe and analyze the clinical effect of cervical paravertebral nerve block combined with Mailuoning and Angelica sinensis injection in treatment of nerve-root type cervical spondylosis. 120 patients who have been accepted by our hospital for nerve-root type cervical spondylosis were selected as research objects. They were randomly divided into a research group and a control group, each containing 60 patients. The control group was applied with glucocorticoid nerve block therapy, while the research group was treated by cervical paravertebral nerve block combined with Mailuoning and Angelica sinensis injection. The total therapeutic response rates of two groups were compared. The total therapeutic response rate of the research group was relatively higher,P<0.05. Through comparing various clinical effect scores between two groups, the research group also had advantages over control group, P<0.05. The treatment satisfaction degree of the research group was also higher than that of control group, P<0.05. The application of cervical paravertebral nerve block combined with Mailuoning and Angelica sinensis injection can achieve better medical results and achieve higher treatment satisfaction degree.

Clinical efficacy of glucosamine hydrochloride tablets in the treatment of cervical spondylosis.

The aim of the stuy was to observe and analyze the effect of glucosamine hydrochloride tablets on patients with cervical spondylosis. This study was conducted on 130 patients diagnosed with cervical spondylosis who were treated in our hospital. The time period was from June 2015 to December 2017. The subjects were randomly divided into a reference group treated with cervical vertebra exercises and cervical occipital belt traction therapy and the study group was further treated with glucosamine hydrochloride tablets. The treatment efficacy of both groups was observed. Comparison of the overall treatment efficiency of patients showed that compared with the reference group, the study group has more significant advantages, P<0.05; comparison of the overall patient satisfaction rate showed that the study group was also superior to the reference group, P<0.05; In addition, statistical analysis of adverse reactions showed no statistically significant difference, P<0.05. The treatment of glucosamine hydrochloride tablets in patients with cervical spondylosis can achieve ideal results, improve the overall treatment efficiency, and thus, has important application significance.

Comparison of clinical effect in treatment of bone tumor between zoledronic acid needle and ibandronate needle.

To observe and analyze the clinical effect of zoledronic acid needle and ibandronate needle in treatment of bone tumor. 100 patients who have been treated in our hospital for bone tumor were selected as research objects. They were randomly divided into research group and control group, each containing 50 patients. The research group was applied with ibandronate needle therapy, while the control group was given with zeledronic acid needle therapy. After treatment, the clinical effects of the two groups were observed and analyzed. Through comparing the pain relief rate after treatment between the two groups, it can be known that the pain relief rate of research group was relatively higher, P<0.05; the rate of adverse effect in research group was relatively lower, P<0.05; the quality of life score (QLS) of research group was significantly superior to that of control group, P<0.05. theibandronate needle therapy is a more reliable and superior method in treatment of bone tumor compared with zoledronic acid needle therapy, which should be promoted in clinical treatment.

Scaffolding protein SPIDR/KIAA0146 connects the Bloom syndrome helicase with homologous recombination repair.

The Bloom syndrome gene product, BLM, is a member of the highly conserved RecQ family. An emerging concept is the BLM helicase collaborates with the homologous recombination (HR) machinery to help avoid undesirable HR events and to achieve a high degree of fidelity during the HR reaction. However, exactly how such coordination occurs in vivo is poorly understood. Here, we identified a protein termed SPIDR (scaffolding protein involved in DNA repair) as the link between BLM and the HR machinery. SPIDR independently interacts with BLM and RAD51 and promotes the formation of a BLM/RAD51-containing complex of biological importance. Consistent with its role as a scaffolding protein for the assembly of BLM and RAD51 foci, cells depleted of SPIDR show increased rate of sister chromatid exchange and defects in HR. Moreover, SPIDR depletion leads to genome instability and causes hypersensitivity to DNA damaging agents. We propose that, through providing a scaffold for the cooperation of BLM and RAD51 in a multifunctional DNA-processing complex, SPIDR not only regulates the efficiency of HR, but also dictates the specific HR pathway.

Enhancing the yield of Xenocoumacin 1 in Xenorhabdus nematophila YL001 by optimizing the fermentation process.

Xenocoumacin 1 (Xcn 1), antibiotic discovered from secondary metabolites of Xenorhabdus nematophila, had the potential to develop into a new pesticide due to its excellent activity against bacteria, oomycetes and fungi. However, the current low yield of Xcn1 limits its development and utilization. To improve the yield of Xcn1, response surface methodology was used to determine the optimal composition of fermentation medium and one factor at a time approach was utilized to optimize the fermentation process. The optimal medium composed of in g/L: proteose peptone 20.8; maltose 12.74; K2HPO4 3.77. The optimal fermentation conditions were that 25 °C, initial pH 7.0, inoculum size 10%, culture medium 75 mL in a 250 mL shake flask with an agitation rate of 150 rpm for 48 h. Xenorhabdus nematophila YL001 was produced the highest Xcn1 yield (173.99 mg/L) when arginine was added to the broth with 3 mmol/L at the 12th h. Compared with Tryptic Soy Broth medium, the optimized fermentation process resulted in a 243.38% increase in Xcn1 production. The obtained results confirmed that optimizing fermentation technology led to an increase in Xcn1 yield. This work would be helpful for efficient Xcn1 production and lay a foundation for its industrial production.

Antifungal Activity and Mechanism of Xenocoumacin 1, a Natural Product from Xenorhabdus nematophila against Sclerotinia sclerotiorum.

Sclerotinia sclerotiorum (Lib.) de Bary, a polyphagous necrotrophic fungal pathogen, has brought about significant losses in agriculture and floriculture. Until now, the most common method for controlling S. sclerotiorum has been the application of fungicides. Xenocoumacin 1 (Xcn1) is a potential biopesticide having versatile antimicrobial activities, generated by Xenorhabdus nematophila. This study was intended to isolate Xcn1 from X. nematophila YL001 and clarify its efficacies for S. sclerotiorum control. Xcn1 demonstrated a wider antifungal spectrum against 10 plant-pathogenic fungi. It also exhibited a strong inhibitory effect on the mycelial growth of S. sclerotiorum with an EC50 value of 3.00 µg/mL. Pot experiments indicated that Xcn1 effectively inhibited disease extension on oilseed rape and broad bean plants caused by S. sclerotiorum. Morphological and ultrastructural observations revealed that the hyphae of S. sclerotiorum became twisted, shriveled, and deformed at the growing points after treatment with Xcn1 at 3.00 µg/mL and that the subcellular fractions also became abnormal concurrently, especially the mitochondrial structure. Moreover, Xcn1 also increased cell membrane permeability and decreased the content of exopolysaccharide as well as suppressing the activities of polygalacturonase and cellulase of S. sclerotiorum, but exerted no effects on oxalic acid production. This study demonstrated that Xcn1 has great potential to be developed as a new biopesticide for the control of S. sclerotiorum.

Preserving genome integrity: The vital role of SUMO-targeted ubiquitin ligases.

Various post-translational modifications (PTMs) collaboratively fine-tune protein activities. SUMO-targeted ubiquitin E3 ligases (STUbLs) emerge as specialized enzymes that recognize SUMO-modified substrates through SUMO-interaction motifs and subsequently ubiquitinate them via the RING domain, thereby bridging the SUMO and ubiquitin signaling pathways. STUbLs participate in a wide array of molecular processes, including cell cycle regulation, DNA repair, replication, and mitosis, operating under both normal conditions and in response to challenges such as genotoxic stress. Their ability to catalyze various types of ubiquitin chains results in diverse proteolytic and non-proteolytic outcomes for target substrates. Importantly, STUbLs are strategically positioned in close proximity to SUMO proteases and deubiquitinases (DUBs), ensuring precise and dynamic control over their target proteins. In this review, we provide insights into the unique properties and indispensable roles of STUbLs, with a particular emphasis on their significance in preserving genome integrity in humans.

Response of vertebral fractures to treatment with denosumab in a patient with postpartum osteoporosis: a case report and literature review.

Postpartum osteoporosis (PO) is a rare condition characterized by low bone mineral density (BMD) and an increased risk of vertebral fragility fracture. We encountered a 34-year-old woman who developed back pain 1 week after delivery. Magnetic resonance imaging of the lumbar spine revealed three vertebral compression fractures. Pretreatment BMD evaluation by dual-energy X-ray absorptiometry revealed a low T-score and Z-score (-2.0 and -2.0, respectively; BMD, 0.876 g/cm2) in the affected region of the spine. The patient was diagnosed with PO and treated with subcutaneous injection of denosumab 60 mg (Prolia; Amgen, Inc., Thousand Oaks, CA, USA) every 6 months. After two treatments, the BMD had significantly increased and the back pain was improved; the patient therefore decided to terminate the treatment. Two months later, her back pain worsened and BMD decreased as measured by dual-energy X-ray absorptiometry examination of the lumbar spine. Therefore, the patient resumed treatment with denosumab, and the BMD of the lumbar spine increased after another two treatments. Therefore, we consider denosumab to be promising in the management of PO with respect to increased BMD and decreased pain.

Aquaporin 1 overexpression may enhance glioma tumorigenesis by interacting with the transcriptional regulation networks of Foxo4, Maz, and E2F families.

BACKGROUND: The glioblastoma has served as a valuable experimental model system for investigating the growth and invasive properties of glioblastoma. Aquaporin-1 (AQP1) in facilitating cell migration and potentially contributing to tumor progression. In this study, we analyzed the role of AQP1 overexpression in glioblastoma and elucidated the main mechanisms involved. METHODS: AQP1 overexpression recombinant vector was introduced into C6 rat glioma cells to construct an AQP1 overexpression C6 cell line, and its effect on cell viability and migration ability was detected by MTT and Transwell. RNA was extracted by Trizol method for gene sequencing and transcriptomics analysis, and the differentially expressed genes (DEGs) were enriched for up- and downregulated genes by Principal component analysis (PCA), and the molecular mechanism of AQP1 overexpression was analyzed in comparison with the control group using the NCBI GEO database. Statistical analysis was performed using Mann-Whitney paired two tailed t test. RESULTS: The cell viability of AQP1-transfected cell lines increased by 23% and the mean distance traveled increased by 67% compared with the control group. Quantitative analysis of gene expression showed that there were 12,121 genes with an average transcripts per million (TPM) value greater than 1. DEGs accounted for 13% of the genes expressed, with the highest correlation with upregulated genes being FOXO4 and MAZ, and the highest with downregulated genes being E2F TFs. CONCLUSIONS: AQP1 may be implicated in glioma formation by interacting with the transcriptional regulation networks involving the FOXO4, MAZ, and E2F1/2. These findings shed light on the potential significance of AQP1 in glioma pathogenesis and warrant further investigations to unravel the underlying molecular mechanisms.

Fibrillarin promotes homologous recombination repair by facilitating the recruitment of recombinase RAD51 to DNA damage sites. / çº¤ç»´è›‹ç™½é€šè¿‡ä¿ƒè¿›é‡ç»„é ¶RAD51在DNA损伤位点的招募参与同源重组修复.

Eukaryotic organisms constantly face a wide range of internal and external factors that cause damage to their DNA. Failure to accurately and efficiently repair these DNA lesions can result in genomic instability and the development of tumors (Canela et al., 2017). Among the various forms of DNA damage, DNA double-strand breaks (DSBs) are particularly harmful. Two major pathways, non-homologous end joining (NHEJ) and homologous recombination (HR), are primarily responsible for repairing DSBs (Katsuki et al., 2020; Li and Yuan, 2021; Zhang and Gong, 2021; Xiang et al., 2023). NHEJ is an error-prone repair mechanism that simply joins the broken ends together (Blunt et al., 1995; Hartley et al., 1995). In contrast, HR is a precise repair process. It involves multiple proteins in eukaryotic cells, with the RAD51 recombinase being the key player, which is analogous to bacterial recombinase A (RecA) (Shinohara et al., 1992). The central event in HR is the formation of RAD51-single-stranded DNA (ssDNA) nucleoprotein filaments that facilitate homology search and DNA strand invasion, ultimately leading to the initiation of repair synthesis (Miné et al., 2007; Hilario et al., 2009; Ma et al., 2017).

Corrigendum: The MYC paralog-PARP1 axis as a potential therapeutic target in MYC paralog-activated small cell lung cancer.

[This corrects the article DOI: 10.3389/fonc.2020.565820.].

Nucleolar GTPase Bms1 displaces Ttf1 from RFB-sites to balance progression of rDNA transcription and replication.

18S, 5.8S, and 28S ribosomal RNAs (rRNAs) are cotranscribed as a pre-ribosomal RNA (pre-rRNA) from the rDNA by RNA polymerase I whose activity is vigorous during the S-phase, leading to a conflict with rDNA replication. This conflict is resolved partly by replication-fork-barrier (RFB)-sites sequences located downstream of the rDNA and RFB-binding proteins such as Ttf1. However, how Ttf1 is displaced from RFB-sites to allow replication fork progression remains elusive. Here, we reported that loss-of-function of Bms1l, a nucleolar GTPase, upregulates rDNA transcription, causes replication-fork stall, and arrests cell cycle at the S-to-G2 transition; however, the G1-to-S transition is constitutively active characterized by persisting DNA synthesis. Concomitantly, ubf, tif-IA, and taf1b marking rDNA transcription, Chk2, Rad51, and p53 marking DNA-damage response, and Rpa2, PCNA, Fen1, and Ttf1 marking replication fork stall are all highly elevated in bms1l mutants. We found that Bms1 interacts with Ttf1 in addition to Rc1l. Finally, we identified RFB-sites for zebrafish Ttf1 through chromatin immunoprecipitation sequencing and showed that Bms1 disassociates the Ttf1‒RFB complex with its GTPase activity. We propose that Bms1 functions to balance rDNA transcription and replication at the S-phase through interaction with Rcl1 and Ttf1, respectively. TTF1 and Bms1 together might impose an S-phase checkpoint at the rDNA loci.

149Sm(n,α)146Nd cross sections in the MeV region.

We have measured the (149)Sm(n,α)(146)Nd cross section at 4.5, 5.0, 5.5, 6.0, and 6.5 MeV. Measurements were performed at the 4.5 MV Van de Graaff accelerator of Peking University with monoenergetic neutrons produced via the (2)H(d,n)(3)He reaction using a deuterium gas target. Alpha particles were detected with a double-section gridded ionization chamber having two back-to-back (149)Sm(2)O(3) samples attached to the common cathode. Absolute neutron flux was measured using a small (238)U fission chamber and monitored by a BF(3) long counter. These are the first reported cross sections for this reaction at these energies, except at 6.0 eV, where our new data are in good agreement with our earlier result. The present results help to much better constrain the (149)Sm(n,α)(146)Nd cross section in a region where its energy dependence is changing fairly rapidly and there are large differences between evaluated nuclear data libraries.

Antimicrobial Activity and Identification of the Biosynthetic Gene Cluster of X-14952B From Streptomyces sp. 135.

The bacterial genus Streptomyces is an important source of antibiotics, and genome mining is a valuable tool to explore the potential of microbial biosynthesis in members of this genus. This study reports an actinomycete strain 135, which was isolated from Qinghai-Tibet Plateau in China and displayed broad antimicrobial activity. The fermentation broth of strain 135 displayed strong antifungal activity (>70%) against Sclerotinia sclerotiorum, Botrytis cinerea, Valsa mali, Phytophthora capsici, Glomerella cingulata, Magnaporthe grisea, Bipolaris maydis, Exserohilum turcicum in vitro, meanwhile possessed significant preventive and curative efficacy against S. sclerotiorum, Gaeumannomyces graminis, and P. capsici on rape leaves (54.04 and 74.18%), wheat (90.66 and 67.99%), and pepper plants (79.33 and 66.67%). X-14952B showed the greatest antifungal activity against S. sclerotiorum and Fusarium graminearum which the 50% inhibition concentration (EC50) were up to 0.049 and 0.04 µg/mL, respectively. Characterization of strain 135 using a polyphasic approach revealed that the strain displayed typical features of the genus Streptomyces. 16S rRNA gene sequencing and phylogenetic analysis demonstrated that the isolate was most closely related to and formed a clade with Streptomyces huasconensis HST28T (98.96% 16S rRNA gene sequence similarity). Average nucleotide identity (ANI) and DNA-DNA hybridization (DDH) values in strain 135 and related type strains were both below the threshold of species determination (91.39 and 56.5%, respectively). OrthoANI values between strain 135 and related type strains are under the cutoff of determining species (<95%). The biosynthetic gene cluster (BGC) designated to X-14952B biosynthesis was identified through genome mining and the possible biosynthesis process was deduced.