Real-world effectiveness of long acting aripiprazole: Treatment persistence and its correlates in the Italian clinical practice

OBJECTIVES

To identify the variables that are associated with persistence to Aripiprazole-Long Acting (A-LAI), in adult patients with schizophrenia.

METHODS

Observational, retrospective, non-interventional study involving 261 patients with schizophrenia.

RESULTS

Eighty-six percent of study subjects were persistent for at least 6 months. All subjects with baseline CGI-S of 1 or 2, 95% of subjects with CGI-S of 3, 86% with CGI-S of 4, 82% of subjects with CGI-S of 5, 73% of subjects with CGI of 6 and 90% of subjects with CGI of 7 were persistent. A-LAI treatment continuation rate was higher in patients with: 1) baseline CGI score ≤ 4; 2) schizophrenia dimension (LDPS) mania score ≤ 5; 3) psychotic spectrum schizoid score ≤ 11.

CONCLUSIONS

A relatively high number of patients (n = 225, 86%) were persistent to A-LAI for at least 6 months. Not surprisingly, very severe patients were more unlikely to be persistent. However, it is noteworthy that a large number of subjects with high CGI score at the time when A-LAI was started (82% of subjects with CGI-S of 5, 73% of subjects with CGI of 6 and 90% of subjects with CGI of 7) were persistent. Larger, controlled, prospective and longer studies are warranted.

Hemostatic abnormalities in patients with Ehlers-Danlos syndrome

Essentials Ehlers-Danlos Syndrome (EDS) is a rare heterogeneous group of inherited collagen disorders. A cohort of EDS patients was investigated for bleeding tendency and hemostatic abnormalities. EDS is associated with an increased risk of bleeding. EDS patients have platelet function abnormalities, whose severity correlates with bleeding risk. SUMMARY: Background Ehlers-Danlos syndrome (EDS) includes a heterogeneous group of connective tissue disorders affecting skin, bones, vessels, and other organs. Patients with EDS have an increased risk of bleeding, but a comprehensive study of hemostasis in EDS patients is lacking. Objective To investigate the bleeding tendency of a cohort of patients with EDS by using the Bleeding Assessment Tool of the ISTH, the bleeding severity score (BSS). Methods The BSS was defined as abnormal when it was ≥ 4 in men and ≥ 6 in women. Patients with a bleeding tendency were compared with those without in terms of type and number of hemostatic abnormalities. Results Fifty-nine of 141 patients with EDS (41.7%) had an abnormal BSS. Prothrombin time and activated partial thromboplastin time were slightly prolonged in 10 patients (7.1%) because of mild coagulation factor deficiencies, which were not responsible for the bleeding diathesis. von Willebrand factor antigen, ristocetin cofactor, endogenous thrombin potential and platelet count were normal in all patients. At least one platelet function abnormality was found in 53 patients (90%) with an abnormal BSS and in 64 (78%) with a normal BSS (adjusted odds ratio [OR] 2.55, 95% confidence interval [CI] 0.87-7.48). The risk of bleeding progressively increased with the number of platelet function abnormalities, reaching an OR of 5.19 (95% CI 1.32-20.45) when more than three abnormalities were detected. Conclusions Our results show that nearly half of patients with EDS have an abnormal BSS, which, in 90% of cases, appear, at least in part, to be attributable to platelet function abnormalities. Abnormalities of primary hemostasis may contribute to the risk of bleeding in patients with EDS.

Processing of DNA Ends in the Maintenance of Genome Stability

DNA double-strand breaks (DSBs) are particularly hazardous lesions as their inappropriate repair can result in chromosome rearrangements, an important driving force of tumorigenesis. DSBs can be repaired by end joining mechanisms or by homologous recombination (HR). HR requires the action of several nucleases that preferentially remove the 5′-terminated strands at both DSB ends in a process called DNA end resection. The same nucleases are also involved in the processing of replication fork structures. Much of our understanding of these pathways has come from studies in the model organism Saccharomyces cerevisiae. Here, we review the current knowledge of the mechanism of resection at DNA DSBs and replication forks.

Tel1/ATM prevents degradation of replication forks that reverse after topoisomerase poisoning

In both yeast and mammals, the topoisomerase poison camptothecin (CPT) induces fork reversal, which has been proposed to stabilize replication forks, thus providing time for the repair of CPT-induced lesions and supporting replication restart. We show that Tel1, the Saccharomyces cerevisiae orthologue of human ATM kinase, stabilizes CPT-induced reversed forks by counteracting their nucleolytic degradation by the MRX complex. Tel1-lacking cells are hypersensitive to CPT specifically and show less reversed forks in the presence of CPT The lack of Mre11 nuclease activity restores wild-type levels of reversed forks in CPT-treated tel1Δ cells without affecting fork reversal in wild-type cells. Moreover, Mrc1 inactivation prevents fork reversal in wild-type, tel1Δ, and mre11 nuclease-deficient cells and relieves the hypersensitivity of tel1Δ cells to CPT Altogether, our data indicate that Tel1 counteracts Mre11 nucleolytic activity at replication forks that undergo Mrc1-mediated reversal in the presence of CPT.

Alkaline Denaturing Southern Blot Analysis to Monitor Double-Strand Break Processing

Generation of 3' single-stranded DNA (ssDNA) tails at the ends of a double-strand break (DSB) is essential to repair the break through accurate homology-mediated repair pathways. Several methods have been developed to measure ssDNA accumulation at a DSB in the budding yeast Saccharomyces cerevisiae. Here, we describe one of these assays, which is based on the inability of restriction enzymes to cleave ssDNA. Digestion of genomic DNA prepared at different time points after DSB generation leads to the formation of ssDNA fragments whose length increases as the 5' strand degradation proceeds beyond restriction sites. After the separation by electrophoresis on alkaline denaturing agarose gel, these ssDNA fragments can be visualized by hybridization with an RNA probe that anneals with the 3'-undegraded DSB strand. This assay allows a direct and comprehensive visualization of DSB end processing.

Patterns of Care and Survival in Non Small Cell Lung Cancer: 15 Years’ Experience in a General Hospital

Background

Transferring results derived from clinical research into practice is particularly difficult in lung cancer where clear indications for treatment are defined only for selected subgroups of patients. Studies on hospital-based lung cancer population could provide data for quantifying this issue.

Patients and methods

This was a follow-up study of consecutive, first-diagnosis cases referred to the in-and outpatient cancer clinics of a large italian general hospital between January 1975 and December 1990. Data were collected from medical records and recorded on ad hoc standardized forms. Analysis focused on changes in distribution over time of patient-related characteristics, prevalence of specific treatment strategies and survival of the study population.

Results

1345 primary non small cell lung cancer cases were reviewed and 1125 were fully evaluable. In early stages (510/1125, 45%) only 237 patients actually underwent surgery. In this group surgery increased from 36 to 69% whereas chemotherapy decreased from 58 to 15%. In the advanced group (615/1125, 55%) chemotherapy was the preferred treatment but combined modalities tripled over time (from 4 to 12%). No significant changes in survival were observed within each group over time.

Conclusion

Despite changes in the therapeutic approaches, mortality from lung cancer does not seem reduced over time. Since the proportion of cases that could potentially benefit from “active” treatments is small, for the large majority of patients a switch in clinical research from a cure to a careoriented strategy should be considered.

Cytogenetic Analysis in 28 Radically Operated Non-Small-Cell Lung Cancer: Preliminary Considerations

Twenty-eight radically operated non-small-cell lung cancer patients were analyzed with regard to chromosomal assessment and DNA content: in 13 cases, different quantitative/ qualitative chromosome alterations were found. In particular, in 12 cases marker chromosomes and cytogenetic abnormalities in euploid cells were demonstrated. The prognostic value of these findings will be aim of further studies.

Cardiac Toxicity of 5-Fluorouracil: A Study on 1083 Patients

The possible onset of cardiotoxic manifestations during chemotherapy with 5-fluorouracil (5-FU) was evaluaetd in 1083 patients treated with the drug for various kinds of neoplasm. We recognized 17 cases of 5-FU cardiopathy (usually anginous crises but also myocardial infarction). The comprehensive incidence was 1.6 %, with a significantly greater risk (4.5 % vs 1.1 %) for patients with a positive anamnesis of previous cardiopathy. On the contrary, age and combination with other antiblastic drugs had no affect on the appearance of cardiopathy. We conclude that 5-FU cardiopathy, although rare, has to be taken into account in oncologic practice, chiefly in those patients already affected with cardiac diseases.

Phase II Study of the Activity and Tolerability of a Combined Regimen of High-Dose Epirubicin and Cisplatin in Stage IIIb and IV Non-Small Cell Lung Cancer

AIM

To explore the feasibility and activity of a combined regimen of high-dose epirubicin and cisplatin as an alternative to current treatments for non-small cell lung cancer (NSCLC).

METHOD

Forty-four patients with stage IIIb or IV NSCLC, median Karnofsky index 90, were enrolled. Epirubicin (60 mg/m2) was administered on days 1 and 2 and cisplatin (100 mg/m2) on day 1. Treatment was repeated every 21 days for a maximum of six cycles. A hematopoietic growth factor (G-CSF) was used only for patients reaching codified nadir count values.

RESULTS

A total of 130 cycles were administered with a mean of 2.9 cycles per patient. Of 41 assessable patients one showed a complete response and 15 had partial responses (overall response rate, 39%). Grade 3 or 4 leukopenia and grade 3 hemoglobin toxicity were seen in 40% and 14%, respectively, of the administered cycles. The most common nonhematologic toxic events were nausea and vomiting, mucositis, anorexia, and asthenia.

CONCLUSIONS

This epirubicin-cisplatin regimen seemed effective and was generally well tolerated, and therefore suitable for use in an outpatient setting.

The RNA binding protein Npl3 promotes resection of DNA double-strand breaks by regulating the levels of Exo1

Eukaryotic cells preserve genome integrity upon DNA damage by activating a signaling network that promotes DNA repair and controls cell cycle progression. One of the most severe DNA damage is the DNA double-strand break (DSB), whose 5΄ ends can be nucleolitically resected by multiple nucleases to create 3΄-ended single-stranded DNA tails that trigger DSB repair by homologous recombination. Here, we identify the Saccharomyces cerevisiae RNA binding protein Npl3 as a new player in DSB resection. Npl3 is related to both the metazoan serine-arginine-rich and the heterogeneous nuclear ribonucleo-proteins. NPL3 deletion impairs the generation of long ssDNA tails at the DSB ends, whereas it does not exacerbate the resection defect of exo1Δ cells. Furthermore, either the lack of Npl3 or the inactivation of its RNA-binding domains causes decrease of the exonuclease Exo1 protein levels as well as generation of unusual and extended EXO1 RNA species. These findings, together with the observation that EXO1 overexpression partially suppresses the resection defect of npl3Δ cells, indicate that Npl3 participates in DSB resection by promoting the proper biogenesis of EXO1 mRNA.

Controlling hybrid nonlinearities in transparent conducting oxides via two-colour excitation

Nanophotonics and metamaterials have revolutionized the way we think about optical space (ε,μ), enabling us to engineer the refractive index almost at will, to confine light to the smallest of the volumes, and to manipulate optical signals with extremely small footprints and energy requirements. Significant efforts are now devoted to finding suitable materials and strategies for the dynamic control of the optical properties. Transparent conductive oxides exhibit large ultrafast nonlinearities under both interband and intraband excitations. Here we show that combining these two effects in aluminium-doped zinc oxide via a two-colour laser field discloses new material functionalities. Owing to the independence of the two nonlinearities, the ultrafast temporal dynamics of the material permittivity can be designed by acting on the amplitude and delay of the two fields. We demonstrate the potential applications of this novel degree of freedom by dynamically addressing the modulation bandwidth and optical spectral tuning of a probe optical pulse.

Metamaterials have enabled the tailored engineering of optical properties. Here, Clerici et al. show that independent interband and intraband nonlinearities in transparent conducting oxides allow dynamic optical control of the real and imaginary parts of the refractive index.

Higher uric acid serum levels are associated with better muscle function in the oldest old: Results from the Mugello Study

BACKGROUND

Sarcopenia is the progressive loss of muscle mass and strength that occurs with advancing age and plays a pivotal role in the causal pathway leading to frailty, disability and, eventually, to death among older persons. As oxidative damage of muscle proteins has been shown to be a relevant contributory factor, in this study we hypothesized that uric acid (UA), a powerful endogenous antioxidant, might exert a protective effect on muscle function in the oldest old and we tested our hypothesis in a group of nonagenarians who participated in the Mugello Study.

METHODS

239 subjects, 73 men and 166 women, mean age 92.8years±SD 3.1, underwent the assessment of UA serum level and isometric handgrip strength, a widely used clinical measure of sarcopenia.

RESULTS

Mean UA serum level was 5.69mg/dL±SD 1.70 and mean handgrip strength was 15.0kg±SD 6.9. After adjusting for relevant confounders, higher UA serum levels remained independent positive predictors of isometric handgrip strength (β 1.24±SE(β) 0.43, p=0.005).

CONCLUSION

Our results show that higher UA serum levels are associated with better muscle function in the oldest old and, accordingly, might slow down the progression of sarcopenia.

Abuse During Childhood and Burnout

Background

Childhood maltreatment is the most important risk factor for the onset of psychiatric disorders. Revictimization is really frequent as well as substance or alcohol abuse, often linked to self-treatment. Accordingly, our pilot study aims to analyze possible implication of childhood maltreatment on resilience and burnout.

Methods

Patients admitted to outpatients psychiatric department in a six month period (1st January 2015–30th June 2015) complaining low to moderate anxiety or depression have been administered childhood trauma questionnaire (CTQ) and Maslach burnout inventory.

Results

CTQ results in 71 (87%) Emotional Neglect (EN), 2 (2.4%) Sexual Abuse (SA) and 2 (2.4%) Physical Abuse (PA). Twenty-one showed high emotional exhaustion, 21 high depersonalization, 9 moderate personal accomplishment while 1 showed low personal accomplishment. None of the patients who suffered child sexual abuse shows depersonalization or personal accomplishment difficulties linked to burnout. Patients negative to CTQ show respectively moderate emotional exhaustion (M = 20 ± 20.15), moderate depersonalization (11 ± 9.42) and high personal accomplishment (17 ± 12.38). Patients who suffered emotional neglect show the poorest profile at Maslach, particularly regarding emotional exhaustion. ANOVA reaches statistical significance among the 3 groups of detected abuse (EN, SA, PA) in personal accomplishment (P = 0.013) confirmed at POST HOC between EN and SA (P = 0.0004).

Conclusion

The results obtained in this pilot study highlight two important considerations. First, it seems urgent to stress the huge prevalence of emotional neglect among those referred to psychiatric outpatient department due to moderate anxiety or depression complain. Moreover, emotional neglect appears to be the most compromised factor of burnout, especially if compared to sexual abuse.

Personality Disorders and Perinatal Psychiatry: Food for Thoughts from Perinatal Psychiatric Department Experience

Background

Pregnancy and postpartum are sensitive unique moments in women's life. Perinatal psychiatry is focused on depression and psychosis, but personality issues is often neglected as well as risk factors for personality disorders instead of being considered causative of onset or recrudescence of psychiatric symptoms in perinatal.

Methods

In total, 129 women were referred to perinatal psychiatric department during their pregnancy or postpartum in the last three years. They were administered SCID II, Childhood Trauma Questionnaire (CTQ), Beck Depression and Anxiety Inventories (BDI and BAI), Edinburgh Postnatal Depression Scale (EPDS) and World Health Organization Quality of Life (WHOQOL). Their interaction with babies was monitored at birth and during follow up. Children's behavioral development is under evaluation through structured tests.

Results

BDI and BAI scored moderate or severe in 31 and 27% of women, EPDS was significant in 36%, while SCID II highlighted 24% of borderline, 17% narcissistic, 4% schizoid, 4% paranoid and 9% obsessive/compulsive PD. Nineteen of them suffered physical abuse during childhood, 26 sexual abuse, 89 emotional neglect and only 15 out of 129 were negative to any kind of abuse during childhood.

Conclusion

Personality disorders appears to influence maternal adjustment to pregnancy and motherhood. Abuses suffered during childhood confirm their role as potential risk factor in personality issues which clearly express their effect in adaptation to change in personal role and in emphatic interactions.

Disclosure of interest

The authors have not supplied their declaration of competing interest.

Immunomodulatory effects of pidotimod in adults with community-acquired pneumonia undergoing standard antibiotic therapy

The morbidity and mortality of community-acquired pneumonia (CAP) are still elevated and two aspects seem to contribute to a worse outcome: an uncontrolled inflammatory reaction and an inadequate immune response. Adjuvants, including corticosteroids and intravenous immunoglobulins, have been proposed to counterbalance these effects but their efficacy is only partial. We examined the immunomodulatory activity of Pidotimod (PDT), a synthetic dipeptide molecule in adult patients hospitalized for CAP. Sixteen patients with a diagnosis of CAP and a PSI score III or IV and/or a CURB-65 0-2 were randomized to receive either levofloxacin 500 mg b.i.d. alone or levofloxacin plus PDT (800mg, 2 daily doses). Blood samples were drawn at baseline (T0), before initiation of therapy, as well as 3 (T3), and 5 (T5) days after initiation of therapy. Immunologic and clinical parameters were analyzed at each time point. Supplementation of antibiotic therapy with PDT resulted in an upregulation of antimicrobial and of immunomodulatory proteins as well as in an increased percentage of Toll like receptor (TLR)2- and TLR4, and of CD80- and CD86-expressing immune cells. Notably, Pidotimod supplementation was also associated with a robust reduction of TNFα-producing immune cells. No significant differences were observed in clinical parameters. These results confirm that supplementation of antibiotic therapy with Pidotimod in patients with CAP results in a potentially beneficial modulation of innate immunity.

Optically induced metal-to-dielectric transition in Epsilon-Near-Zero metamaterials

Epsilon-Near-Zero materials exhibit a transition in the real part of the dielectric permittivity from positive to negative value as a function of wavelength. Here we study metal-dielectric layered metamaterials in the homogenised regime (each layer has strongly subwavelength thickness) with zero real part of the permittivity in the near-infrared region. By optically pumping the metamaterial we experimentally show that close to the Epsilon-Near-Zero (ENZ) wavelength the permittivity exhibits a marked transition from metallic (negative permittivity) to dielectric (positive permittivity) as a function of the optical power. Remarkably, this transition is linear as a function of pump power and occurs on time scales of the order of the 100 fs pump pulse that need not be tuned to a specific wavelength. The linearity of the permittivity increase allows us to express the response of the metamaterial in terms of a standard third order optical nonlinearity: this shows a clear inversion of the roles of the real and imaginary parts in crossing the ENZ wavelength, further supporting an optically induced change in the physical behaviour of the metamaterial.

Enhanced Nonlinear Refractive Index in ε-Near-Zero Materials

New propagation regimes for light arise from the ability to tune the dielectric permittivity to extremely low values. Here, we demonstrate a universal approach based on the low linear permittivity values attained in the ε-near-zero (ENZ) regime for enhancing the nonlinear refractive index, which enables remarkable light-induced changes of the material properties. Experiments performed on Al-doped ZnO (AZO) thin films show a sixfold increase of the Kerr nonlinear refractive index (n_{2}) at the ENZ wavelength, located in the 1300 nm region. This in turn leads to ultrafast light-induced refractive index changes of the order of unity, thus representing a new paradigm for nonlinear optics.

Upregulation of inflammasome activity and increased gut permeability are associated with obesity in children and adolescents

BACKGROUND

Immune activation contributes to the persistent state of inflammation associated with metabolic dysfunction in obesity. The specific immune receptors that sense metabolic stress signals and trigger inflammation are nevertheless largely unknown, and little is known on inflammatory and immune gene regulation in obesity.

METHODS

The study includes a cross-sectional and a longitudinal arm. Forty children and adolescents were enrolled: 22 obese subjects and 18 age-matched normal weight controls. Obese subjects participated in an 18-month therapeutic protocol, based on intensive lifestyle modification (dietary regimen, physical activity and behavioral interventions). Expression of genes involved in the inflammasome pathway, plasma concentration of the inflammasome-associated pro-inflammatory cytokines (interleukin (IL)-1β and IL-18) and indexes of microbial translocation (lipopolysaccharide (LPS), soluble CD14 (sCD14) and intestinal fatty acid-binding protein) were analyzed at baseline in obese subjects compared with controls, and after 18 months in obese subjects.

RESULTS

Cross-sectional analyses showed that the LPS-induced expression of genes involved in inflammasome (NLRP3, caspase 5 and NAIP), Nod-like receptors (NLRX1 and NOD1), downstream signaling (P2RX7, RAGE, RIPk2, TIRAP and BIRC2) and effector molecules (IFN-γ, IL-12β, IL-1β, CCL2, CCL5, IL-6 and TNFα) was significantly increased in obese subjects at baseline as compared with normal weight controls. The baseline plasma concentration of inflammasome-related cytokines (IL-1β and IL-18) and of microbial translocation markers (LPS and sCD14) was augmented in obese subjects as compared with controls as well. Longitudinal analyses indicated that intensive lifestyle modification resulted in a normalization of parameters in subjects with a significant reduction of BMI after 18 months.

CONCLUSIONS

In children and adolescents, obesity is characterized by the activation of the inflammasome and by an alteration of gut permeability. Successful lifestyle modification is effective in reducing inflammation, suggesting that inhibition of the inflammasome may be a potential therapeutic strategy in obesity.

The thrombin generation assay distinguishes inhibitor from non-inhibitor patients with severe haemophilia A

INTRODUCTION

Patients with haemophilia A (HA) have impaired thrombin generation (TG) capacity and TG assay (TGA) values are linearly related to plasma factor VIII (FVIII) levels.

AIM

This study carried out in patients with unmeasurable FVIII (<1 IU dL(-1) ) was aimed at unravelling any difference in TG capacity in patients with or without inhibitors.

METHODS

Blood samples were collected from patients in a non-bleeding state, after a 5-day wash-out period from last treatment.

RESULTS

TGA was performed in 102 patients with severe HA (15% with high-responding inhibitors; 51% with null F8 mutations, that as expected were more prevalent in inhibitor than in non-inhibitor patients). TG capacity was significantly lower in inhibitor than non-inhibitor patients and in those with null mutations than in those with non-null mutations. When the TG capacity was evaluated only in patients with null mutations with and without inhibitors it was lower in the presence of inhibitors.

CONCLUSIONS

This study shows a greater TG impairment in inhibitor patients irrespective of FVIII levels, inhibitor titre and F8 mutation type, suggesting a role for the TGA in unravelling functional interferences of anti-FVIII inhibitors on coagulation system activation.

Tel1 and Rif2 Regulate MRX Functions in End-Tethering and Repair of DNA Double-Strand Breaks

The cellular response to DNA double-strand breaks (DSBs) is initiated by the MRX/MRN complex (Mre11-Rad50-Xrs2 in yeast; Mre11-Rad50-Nbs1 in mammals), which recruits the checkpoint kinase Tel1/ATM to DSBs. In Saccharomyces cerevisiae, the role of Tel1 at DSBs remains enigmatic, as tel1Δ cells do not show obvious hypersensitivity to DSB-inducing agents. By performing a synthetic phenotype screen, we isolated a rad50-V1269M allele that sensitizes tel1Δ cells to genotoxic agents. The MR^V1269MX complex associates poorly to DNA ends, and its retention at DSBs is further reduced by the lack of Tel1. As a consequence, tel1Δ rad50-V1269M cells are severely defective both in keeping the DSB ends tethered to each other and in repairing a DSB by either homologous recombination (HR) or nonhomologous end joining (NHEJ). These data indicate that Tel1 promotes MRX retention to DSBs and this function is important to allow proper MRX-DNA binding that is needed for end-tethering and DSB repair. The role of Tel1 in promoting MRX accumulation to DSBs is counteracted by Rif2, which is recruited to DSBs. We also found that Rif2 enhances ATP hydrolysis by MRX and attenuates MRX function in end-tethering, suggesting that Rif2 can regulate MRX activity at DSBs by modulating ATP-dependent conformational changes of Rad50.

This study reveals novel roles for the checkpoint kinase Tel1/ATM and Rif2 in regulating the function of the MRX complex during repair of DNA double-strand breaks by nonhomologous end joining and homologous recombination.

Many tumors contain mutations that confer defects in repairing DNA double-strand breaks (DSBs). In both yeast and mammals, the MRX/MRN complex (Mre11-Rad50-Xrs2 in yeast; Mre11-Rad50-Nbs1 in mammals) plays critical functions in repairing a DSB by either nonhomologous end joining (NHEJ) or homologous recombination (HR). Furthermore, it recruits the checkpoint kinase Tel1/ATM. Although ATM is considered to be a tumor suppressor, up-regulation of ATM signaling promotes chemoresistance, radioresistance and metastasis. For this reason, cancer therapies targeting ATM have been developed to increase the effectiveness of standard genotoxic treatments and/or to set up synthetic lethal approaches in cancers with DNA repair defects. We aimed to identify the precise role of ATM/Tel1 in these processes. By performing a synthetic phenotype screen, we identified a mutation (rad50-V1269M) altering the Rad50 subunit of the MRX complex, which sensitizes cells lacking Tel1 to genotoxic agents. Genetic and biochemical characterization of MR^V1269MX protein complex revealed that Tel1 promotes MRX association at DSBs to allow proper MRX-DNA binding that is needed for DSB repair. The role of Tel1 in promoting MRX retention on DSBs is counteracted by Rif2, which can regulate MRX activity at DSBs by modulating ATP-dependent conformational changes in Rad50. Our finding that MRX dysfunctions can be synthetically lethal with Tel1 loss in the presence of genotoxic agents suggests that ATM inhibitors could be beneficial in patients whose tumors have defective MRN functions.

Sae2 Function at DNA Double-Strand Breaks Is Bypassed by Dampening Tel1 or Rad53 Activity

The MRX complex together with Sae2 initiates resection of DNA double-strand breaks (DSBs) to generate single-stranded DNA (ssDNA) that triggers homologous recombination. The absence of Sae2 not only impairs DSB resection, but also causes prolonged MRX binding at the DSBs that leads to persistent Tel1- and Rad53-dependent DNA damage checkpoint activation and cell cycle arrest. Whether this enhanced checkpoint signaling contributes to the DNA damage sensitivity and/or the resection defect of sae2Δ cells is not known. By performing a genetic screen, we identify rad53 and tel1 mutant alleles that suppress both the DNA damage hypersensitivity and the resection defect of sae2Δ cells through an Sgs1-Dna2-dependent mechanism. These suppression events do not involve escaping the checkpoint-mediated cell cycle arrest. Rather, defective Rad53 or Tel1 signaling bypasses Sae2 function at DSBs by decreasing the amount of Rad9 bound at DSBs. As a consequence, reduced Rad9 association to DNA ends relieves inhibition of Sgs1-Dna2 activity, which can then compensate for the lack of Sae2 in DSB resection and DNA damage resistance. We propose that persistent Tel1 and Rad53 checkpoint signaling in cells lacking Sae2 increases the association of Rad9 at DSBs, which in turn inhibits DSB resection by limiting the activity of the Sgs1-Dna2 resection machinery.

Genome instability is one of the most pervasive characteristics of cancer cells and can be due to DNA repair defects and failure to arrest the cell cycle. Among the many types of DNA damage, the DNA double strand break (DSB) is one of the most severe, because it can cause mutations and chromosomal rearrangements. Generation of DSBs triggers a highly conserved mechanism, known as DNA damage checkpoint, which arrests the cell cycle until DSBs are repaired. DSBs can be repaired by homologous recombination, which requires the DSB ends to be nucleolytically processed (resected) to generate single-stranded DNA. In Saccharomyces cerevisiae, DSB resection is initiated by the MRX complex together with Sae2, whereas more extensive resection is catalyzed by both Exo1 and Dna2-Sgs1. The absence of Sae2 not only impairs DSB resection, but also leads to the hyperactivation of the checkpoint proteins Tel1/ATM and Rad53, leading to persistent cell cycle arrest. In this manuscript we show that persistent Tel1 and Rad53 signaling activities in sae2Δ cells cause DNA damage hypersensitivity and defective DSB resection by increasing the amount of Rad9 bound at the DSBs, which in turn inhibits the Sgs1-Dna2 resection machinery. As ATM inhibition has been proposed as a strategy for cancer treatment, the finding that defective Tel1 signaling activity restores DNA damage resistance in sae2Δ cells might have implications in cancer therapies that use ATM inhibitors for synthetic lethal approaches that are devised to kill tumor cells with defective DSB repair.

Resection is responsible for loss of transcription around a double-strand break in Saccharomyces cerevisiae

Emerging evidence indicate that the mammalian checkpoint kinase ATM induces transcriptional silencing in cis to DNA double-strand breaks (DSBs) through a poorly understood mechanism. Here we show that in Saccharomyces cerevisiae a single DSB causes transcriptional inhibition of proximal genes independently of Tel1/ATM and Mec1/ATR. Since the DSB ends undergo nucleolytic degradation (resection) of their 5'-ending strands, we investigated the contribution of resection in this DSB-induced transcriptional inhibition. We discovered that resection-defective mutants fail to stop transcription around a DSB, and the extent of this failure correlates with the severity of the resection defect. Furthermore, Rad9 and generation of γH2A reduce this DSB-induced transcriptional inhibition by counteracting DSB resection. Therefore, the conversion of the DSB ends from double-stranded to single-stranded DNA, which is necessary to initiate DSB repair by homologous recombination, is responsible for loss of transcription around a DSB in S. cerevisiae.