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Glacier retreat has increased in the European Alps during the last four decades. This affects proglacial geomorphic processes and the spatial distribution of plants. We assessed how the type and the magnitude of geomorphic disturbance control the spatial distribution of a rare alpine plant species: Trifolium saxatile All., whose main habitats are proglacial forelands and alluvial bars and banks, within the Glacier Blanc et Glacier Noir catchment area (Ecrins National Park, French Alps). Based on field observations during the summers of 2020 and 2021, we produced a map combining geomorphological deposits and presence-absence of T. saxatile to detect which geomorphological units are relevant for our study. We determined the magnitude and frequency of superficial sediment reworking between the 2020 and 2021 summers using Radio Frequency IDentification experimentation on moraines slopes and glacio-fluvial deposits on which populations of T. saxatile were observed. Abundance and functional traits (stem height, length and number of inflorescences) were also measured. To analyze the potential impacts of geomorphic disturbances on T. saxatile presence, abundance and intra-specific trait variability, generalized linear mixed models (GLMM) and factor analyses of mixed data (FAMD) were used. Results showed heterogeneity in the geographical distribution of T. saxatile within the proglacial landscape. Clovers preferentially established over three geomorphological units: (i) nearly stabilized lateral moraines, (ii) active braided floodplains and (iii) the exposed young alluvial bars. It was totally absent in purely gravitational landforms (e.g. scree, talus cones). The largest individuals of T. saxatile with many inflorescences were mostly found within the active torrential channel where geomorphic disturbances are intense and frequent but this was however balanced by a low abundance of individuals. On lateral moraines and alluvial terraces, which are almost stabilized and exhibit a lower level of geomorphic disturbances than the active braided floodplain (in terms of magnitude and frequency of movement of RFID tracked sediment particles), individuals were much more abundant, but they were smaller and with less inflorescences compared to the active torrential channel. This study shows the importance of geomorphic processes as key drivers of the spatial distribution, and potentially traits expression, of alpine species living in glaciated catchment areas.

Resume Introduction Actuellement, le cancer localise de la corde vocale est traite par radiotherapie ou par chirurgie endoscopique. Ces deux modalites ont prouve leur interet chez le patient âge, la place exacte de chaque traitement est peu documentee. Cette etude evalue notre prise en charge des patients tres âges, atteints d’un cancer des cordes vocales. Materiel et methodes Etude retrospective monocentrique des patients âges de 75 ans ou plus, traites par radiotherapie ou chirurgie endoscopique a visee curative, pour un cancer localise de la corde vocale entre 2004 et 2018. Resultats Trente-trois patients, 27 hommes et 6 femmes, d’âge moyen 82,2 ans (76,1–93,1) ont ete inclus. Vingt-quatre patients ont ete traites par radiotherapie et 9 par chirurgie. Le seul facteur influencant le choix de traitement etait l’invasion de la commissure anterieure. La survie globale etait de 87 % a 2 ans et 62 % a 5 ans. Dix-neuf pour cent des patients ont recidive dans les 5 ans, necessitant des revisions chirugicales. Aucun deces lie au traitement n’a ete note. Le traitement par radiotherapie etait plus pourvoyeur de complications locales aigues, avec deux interruptions temporaires de traitement, et un traitement non mene a son terme. Le traitement par chirurgie etait plus pourvoyeur de dysphonies, retrouvees chez 80 % des patients operes. Conclusion Le traitement du cancer localise de la corde vocale du sujet âge peut se faire par radiotherapie ou par chirurgie endoscopique. L’âge ne doit pas modifier la prise en charge de ces patients. Le traitement chirurgical, plus court, est mieux tolere, mais plus nocif pour la voix et pourra etre privilegie chez les patients les plus comorbides.

Resume La pandemie de COVID-19 impose une reorganisation majeure de l’ensemble de notre systeme de soins. En France, des regles generales ont ete diffusees au niveau national et sont declinees par chaque etablissement, public comme prive, sur l’ensemble du territoire. Ces recommandations, redigees par un groupe d’experts sous l’egide de l’Association francophone de chirurgie endocrinienne (AFCE), ont pour objectif de proposer des principes specifiques de prise en charge chirurgicale au cours et au decours de l’epidemie de COVID- 19, pour les pathologies chirurgicales de la thyroide, des parathyroides, du pancreas endocrine, et des surrenales.

Background The observation that COPD is an independent risk factor for cardiovascular disease (CVDs) comes from comparisons between smokers with COPD and smokers without COPD. The mechanisms that explain increased risk of CVD in patients with COPD are still unclear. Objectives The goal of this study was to assess systemic arterial stiffness (a predictor of CVD mortality) and to evaluate its determinants in a group of patients with mild to moderate COPD secondary to organic dust exposure, tobacco smoking, or both. Methods Systemic arterial stiffness was assessed by using aortic pulse wave velocity (aPWV). Measurements were made in 142 patients with COPD and 155 healthy control subjects matched for age, sex, BMI, and tobacco smoking, exposed to tobacco smoking (n = 56/70 for COPD/control subjects, respectively), organic dusts (n = 44/48), or both (n = 42/37). Results aPWV was higher in COPD than in healthy controls in subjects exposed to tobacco smoking and to both organic dusts and tobacco smoking. By contrast, among never smokers exposed to organic dusts, patients with COPD and matched control subjects had similar aPWV. Multivariate analysis of the 142 patients with COPD (exposed to tobacco smoking and/or to organic dusts) showed that tobacco smoking was associated with high aPWV. Moreover, soluble suppression of tumorigenicity 2, a marker of major cardiovascular events, was correlated with aPWV in these patients. Conclusions Analysis of an unselected group of patients with COPD with different causes suggests that: (1) COPD by itself is not sufficient to explain increased aPWV; and (2) tobacco smoking is a risk factor for elevated aPWV in COPD.

In preparation for mitotic cell division, the nuclear DNA of human cells is compacted into individualized, X-shaped chromosomes1. This metamorphosis is driven mainly by the combined action of condensins and topoisomerase IIα (TOP2A)2,3, and has been observed using microscopy for over a century. Nevertheless, very little is known about the structural organization of a mitotic chromosome. Here we introduce a workflow to interrogate the organization of human chromosomes based on optical trapping and manipulation. This allows high-resolution force measurements and fluorescence visualization of native metaphase chromosomes to be conducted under tightly controlled experimental conditions. We have used this method to extensively characterize chromosome mechanics and structure. Notably, we find that under increasing mechanical load, chromosomes exhibit nonlinear stiffening behaviour, distinct from that predicted by classical polymer models4. To explain this anomalous stiffening, we introduce a hierarchical worm-like chain model that describes the chromosome as a heterogeneous assembly of nonlinear worm-like chains. Moreover, through inducible degradation of TOP2A5 specifically in mitosis, we provide evidence that TOP2A has a role in the preservation of chromosome compaction. The methods described here open the door to a wide array of investigations into the structure and dynamics of both normal and disease-associated chromosomes.

Background Enhanced recovery programs (ERPs) imply early discharge but few papers have assessed the effect of ERPs on post-discharge mortality (PDM). Methods A multicenter nationwide case control study based on administrative data was carried out between March and December 2019. Coding for every episode of care whether in the setting of ERP or not is mandatory for hospital funding (public or private). Twelve surgical specialties or procedures were included. The episodes of care coded with ERP were matched with those without ERP code for several factors such as the type of hospital (public or private), age, gender, month of discharge, and updated Charlson score. Ninety-day PDM was the main outcome. Results Of 420,031 patients in the database, 78,119 had an ERP code. Finally, 132,600 patients with 66,300 matched pairs were considered for the study. Overall, PDM was significantly reduced after ERPs: 0.075% vs 0.138% (p = 0.00042). Significant one-half and two-thirds reduction in PDM was observed respectively after hip arthroplasty (odds ratio 0.48 [95% CI 0.21–0.99]) and colectomy (odds ratio 0.36 [95% CI 0.16–0.74]). Conclusion The findings, based on a large database and a rigorous matching, strongly suggest that ERPs reduce PDM particularly after colectomy and hip arthroplasty. This is likely due to better post-operative care in ERPs.

In preparation for mitotic cell division, the nuclear DNA of human cells is compacted into individualized, X-shaped chromosomes

Resume La preparation preoperatoire du patient avant chirurgie majeure peut etre optimisee par une approche multimodale, telle que la « prehabilitation ». Elle consiste en un programme d’une duree de 4 semaines, comprenant une prise en charge medicale (amelioration des comorbidites), une preparation physique (exercices personnalises en resistance et en endurance), une preparation nutritionnelle (apport d’au moins 1 g/kg/j d’apport de proteines) et un soutien psychologique (prise en charge de l’anxiete). Ces divers renforcements permettent d’amener le patient a l’intervention dans de meilleures conditions. La mise en œuvre d’un programme de prehabilitation necessite toutefois de repenser le parcours preoperatoire du patient : « identification » au plus tot des patients eligibles, organisation de l’ensemble des consultations initiales et du suivi, maintien d’un lien avec l’hopital pendant le programme, personnalisation du projet therapeutique. Notre etablissement est passe en 18 mois d’une phase pilote a une proposition en routine pour certains actes. Cette experience et les elements mis en place nous semblent interessants a partager car ce programme de prehabilitation precede logiquement la rehabilitation rapide postoperatoire ayant pour objectif final une diminution des complications et un retour au domicile dans de meilleures conditions physiques.

Resume Cette etude retrospective a analyse l’impact medico-economique du developpement de la chirurgie ambulatoire en considerant l’ensemble du parcours patient pendant et 3 mois apres l’hospitalisation. Elle a porte sur 11 actes cibles, realises entre le 1er avril 2013 et le 30 septembre 2016. La chirurgie ambulatoire (CA) a eu un impact significatif sur les couts de production hospitaliers qui ont baisse de 20 % en moyenne (23 % dans le secteur prive 18 % dans le secteur public). L’assurance maladie beneficie peu du developpement de la CA du fait de la convergence tarifaire effective depuis 2014. L’economie pour les patients est de 31 a 57 euros selon les actes. La chirurgie ambulatoire a peu d’impact en termes de consommation de soins. L’objectif des 70 % necessitera de revoir l’equation economique a l’aide d’un programme de redistribution plus equitable et pertinent entre les professionnels de sante, les etablissements, les patients et l’assurance maladie.

The glucosinolate (GL) profiles of wild and cultivated Brassica montana Pourret (seed, stem, leaf, root) from southern France were established using LC-MS analysis. In this investigation we have co...

In the version of this article initially published, Extended Data Fig. 5 was a duplicate of Extended Data Fig. 6. The correct image is now in place in the HTML and PDF versions of the article.

Background Study of the medico economic impact of enhanced rehabilitation after surgery (ERAS), by comparing the cost of patient care with or without ERAS, both from the point of view of the hospitals and the Social Security Health Insurance Program. Methods Retrospective longitudinal study on matched data from March 1, 2019 to December 31, 2019. The data are extracted from the French prospective payment system. We studied 12 of the most commonly performed in ERAS business segments. The primary outcome was the reduction of the average length of hospital stay and its implications on production costs and excess capacity. We also studied the impact on hospital incomes and Social Security Insurance Program expenses. The potential gain in hospital days was computed by comparing the length of stay of ERAS and non-ERAS cases. The cost reduction was estimated using the mean number of avoidable days of hospitalization, and the mean cost of the stays obtained from the national cost study. Finally, we studied an approximation of the additional expense for the Social Security Health Insurance Program on costs standardized by applying public sector rates. Results The average length of stay reduction attributed to ERAS is 1.45 (CI 95% 1.42 to 1.48) day per stay, translating to a cost reduction for the hospitals of € 1060 (CI 95% 995 to 1125) per patient and a total of €65 million (CI 95% 61 to 69). At the same time, the additional expenses for the Social Security Insurance Program can conservatively be approximated to € 1.6 million, breaking into a € 2.2 million increase partially compensated by cost savings of € 0.6 million over subsequent stays for complications. Overall, for each percent of additional ERAS activity over the scope of the study, the marginal cost reduction for the hospitals can be estimated to € 1.8 million (CI 95% 1.7 million to 2.0 million). Conclusions Associated with previously known clinical benefits for the patients, these convincing results in terms of economic gain strongly support expanding the adoption of ERAS.

Additional file 1.

International audience; Following SARS-CoV-2 emergence in China, a specific surveillance was implemented in France. Phylogenetic analysis of sequences retrieved through this surveillance suggests that detected initial introductions, involving non-clade G viruses, did not seed local transmission. Nevertheless, identification of clade G variants subsequently circulating in the country, with the earliest from a patient who neither travelled to risk areas nor had contact with travellers, suggests that SARS-CoV-2 might have been present before the first recorded local cases.

Following the emergence of coronavirus disease (COVID-19) in Wuhan, China in December 2019, specific COVID-19 surveillance was launched in France on January 10, 2020. Two weeks later, the first three imported cases of COVID-19 into Europe were diagnosed in France. We sequenced 97 severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) genomes from samples collected between January 24 and March 24, 2020 from infected patients in France. Phylogenetic analysis identified several early independent SARS-CoV-2 introductions without local transmission, highlighting the efficacy of the measures taken to prevent virus spread from symptomatic cases. In parallel, our genomic data reveals the later predominant circulation of a major clade in many French regions, and implies local circulation of the virus in undocumented infections prior to the wave of COVID-19 cases. This study emphasizes the importance of continuous and geographically broad genomic sequencing and calls for further efforts with inclusion of asymptomatic infections.

International audience; Faithful chromosome segregation requires that the sister chromatids be disjoined completely. Defective disjunction can lead to the persistence of histone-free threads of DNA known as ultra-fine bridges (UFBs) that connect the separating sister DNA molecules during anaphase. UFBs arise at specific genomic loci and can only be visualized by detection of associated proteins such as PICH, BLM, topoisomerase IIIα, and RPA. However, it remains unknown how these proteins work together to promote UFB processing. We used a combination of ensemble biochemistry and new single-molecule assays to reconstitute key steps of UFB recognition and processing by these human proteins in vitro. We discovered characteristic patterns of hierarchical recruitment and coordinated biochemical activities that were specific for DNA structures modeling UFBs arising at either centromeres or common fragile sites. Our results describe a mechanistic model for how unresolved DNA replication structures are processed by DNA-structure-specific binding factors in mitosis to prevent pathological chromosome nondisjunction.

Summary PICH is a DNA translocase necessary for the resolution of ultrafine anaphase DNA bridges and to ensure the fidelity of chromosomal segregation. Here, we report the generation of an animal model deficient for PICH that allowed us to investigate its physiological relevance. Pich KO mice lose viability during embryonic development due to a global accumulation of DNA damage. However, despite the presence of chromosomal instability, extensive p53 activation, and increased apoptosis throughout the embryo, Pich KO embryos survive until day 12.5 of embryonic development. The absence of p53 failed to improve the viability of the Pich KO embryos, suggesting that the observed developmental defects are not solely due to p53-induced apoptosis. Moreover, Pich-deficient mouse embryonic fibroblasts exhibit chromosomal instability and are resistant to RASV12/E1A-induced transformation. Overall, our data indicate that PICH is essential to preserve chromosomal integrity in rapidly proliferating cells and is therefore critical during embryonic development and tumorigenesis., Graphical Abstract, Highlights • Pich is essential for embryonic development • Pich KO embryos exhibit DNA damage, p53 activation, and apoptosis • Pich heterozygous mice are born at sub-Mendelian ratios • Pich-deficient MEF are resistant to RASV12/E1A-induced transformation, Albers et al. show that PICH is essential for mouse embryonic development and that PICH deficiency limits oncogenic-induced cellular transformation. These findings suggest that PICH activity is critical during events requiring rapid cell proliferation such as embryonic development and tumorigenesis.

The anaphase of mitosis is one of the most critical stages of the cell division cycle in that it can reveal precious information on the fate of a cell lineage. Indeed, most types of nuclear DNA segregation defects visualized during anaphase are manifestations of genomic instability and augur dramatic outcomes, such as cell death or chromosomal aberrations characteristic of cancer cells. Although chromatin bridges and lagging chromatin are always pathological (generating aneuploidy or complex genomic rearrangements), the main subject of this article, the ultrafine anaphase bridges, might, in addition to potentially driving genomic instability, play critical roles for the maintenance of chromosome structure in rapidly proliferating cells.

Nitric oxide (NO) donors may be useful for treating pulmonary hypertension (PH) complicating sickle cell disease (SCD), as endogenous NO is inactivated by hemoglobin released by intravascular hemolysis. Here, we investigated the effects of the new NO donor NCX1443 on PH in transgenic SAD mice, which exhibit mild SCD without severe hemolytic anemia. In SAD and wild-type (WT) mice, the pulmonary pressure response to acute hypoxia was similar and was abolished by 100 mg/kg NCX1443. The level of PH was also similar in SAD and WT mice exposed to chronic hypoxia (9% O2) alone or with SU5416 and was similarly reduced by daily NCX1443 gavage. Compared with WT mice, SAD mice exhibited higher levels of HO-1, endothelial NO synthase, and PDE5 but similar levels of lung cyclic guanosine monophosphate. Cultured pulmonary artery smooth muscle cells from SAD mice grew faster than those from WT mice and had higher PDE5 protein levels. Combining NCX1443 and a PDE5 inhibitor suppressed the growth rate difference between SAD and WT cells and induced a larger reduction in hypoxic PH severity in SAD than in WT mice. By amplifying endogenous protective mechanisms, NCX1443 in combination with PDE5 inhibition may prove useful for treating PH complicating SCD.

As cells enter mitosis, chromatin compacts to facilitate chromosome segregation yet remains transcribed. Transcription supercoils DNA to levels that can impede further progression of RNA polymerase II (RNAPII) unless it is removed by DNA topoisomerase 1 (TOP1). Using ChIP-seq on mitotic cells, we found that TOP1 is required for RNAPII translocation along genes. The stimulation of TOP1 activity by RNAPII during elongation allowed RNAPII clearance from genes in prometaphase and enabled chromosomal segregation. Disruption of the TOP1-RNAPII interaction impaired RNAPII spiking at promoters and triggered defects in the post-mitotic transcription program. This program includes factors necessary for cell growth, and cells with impaired TOP1-RNAPII interaction are more sensitive to inhibitors of mTOR signaling. We conclude that TOP1 is necessary for assisting transcription during mitosis with consequences for growth and gene expression long after mitosis is completed. In this sense, TOP1 ensures that cellular memory is preserved in subsequent generations.

The preoperative period may be an opportune period to optimize patients’ physical condition with a multimodal preoperative program. The impact of a “prehabilitation” program on elderly patients is discussed. This mono-center observational cohort study included consecutively 139 patients planned for major abdominal and thoracic surgery, with 44 in the control group (age &lt, 65) and 95 in the elderly group (age &gt, 65). All patients followed a “prehabilitation” program including exercise training, nutritional optimization, psychological support, and behavioral change. Seventeen patients in the control group and 45 in the elderly group completed the study at six months. The 6-minute walk test (6 MWT) increased in both groups from the initial evaluation to the last (median value of 80 m (interquartile range 51) for those under 65 years, 59 m (34) for the elderly group, p = 0.114). The 6 MWT was also similar after one month of prehabilitation for both populations. The rate of postoperative complications was similar in the two groups. Prehabilitation showed equivalence in patients over 65 years of age compared to younger patients in terms of increase in functional capabilities and of postoperative evolution. This multimodal program represents a bundle of care that can benefit a frailer population.

Introduction La rehabilitation amelioree apres chirurgie (RAC) se developpe partout dans le monde. Mais a ce jour, et a notre connaissance, aucune etude nationale ou europeenne n’a reellement evalue le degre de diffusion de la RAC dans la pratique quotidienne. Le but de cette etude a grande echelle etait d’analyser le taux d’implementation de la RAC dans diverses specialites chirurgicales et secteurs (public/prive). Methode Il s’agit d’une etude retrospective sur les sejours PMSI (mars–decembre 2019). Les criteres d’inclusion etaient les sejours combinant racines de GHM et actes CCAM avec ou sans codage RAC. Etaient calcule le taux de sejours avec un parcours RAC. Resultats Un total de 420 031 sejours etaient retrouves, dont 78 119 RAC. Les taux d’implementation etaient > 20 % en chirurgie de la hanche et du genou, 10–20 % en chirurgie bariatrique, chirurgie colorectale avec anastomose, prothese d’epaule, hernie rachidienne, hysterectomie pour tumeur, prostatectomie, resection pulmonaire, et Conclusions Cette etude nationale a grande echelle, la premiere de ce type, permet d’apprecier la diffusion de la RAC en France. Cette diffusion est encore insuffisante notamment dans le secteur public. Du fait des avantages demontres de la RAC en termes de reduction de la morbi-mortalite et la duree de sejour, plus d’efforts de pedagogie sont necessaire pour ameliorer l’implementation de la RAC en France.

The observation that COPD is an independent risk factor for cardiovascular disease (CVDs) comes from comparisons between smokers with COPD and smokers without COPD. The mechanisms that explain increased risk of CVD in patients with COPD are still unclear.The goal of this study was to assess systemic arterial stiffness (a predictor of CVD mortality) and to evaluate its determinants in a group of patients with mild to moderate COPD secondary to organic dust exposure, tobacco smoking, or both.Systemic arterial stiffness was assessed by using aortic pulse wave velocity (aPWV). Measurements were made in 142 patients with COPD and 155 healthy control subjects matched for age, sex, BMI, and tobacco smoking, exposed to tobacco smoking (n = 56/70 for COPD/control subjects, respectively), organic dusts (n = 44/48), or both (n = 42/37).aPWV was higher in COPD than in healthy controls in subjects exposed to tobacco smoking and to both organic dusts and tobacco smoking. By contrast, among never smokers exposed to organic dusts, patients with COPD and matched control subjects had similar aPWV. Multivariate analysis of the 142 patients with COPD (exposed to tobacco smoking and/or to organic dusts) showed that tobacco smoking was associated with high aPWV. Moreover, soluble suppression of tumorigenicity 2, a marker of major cardiovascular events, was correlated with aPWV in these patients.Analysis of an unselected group of patients with COPD with different causes suggests that: (1) COPD by itself is not sufficient to explain increased aPWV; and (2) tobacco smoking is a risk factor for elevated aPWV in COPD.

The glucosinolate (GL) profiles of wild and cultivated

Bloom syndrome, caused by biallelic mutations in BLM, is characterized by prenatal-onset growth deficiency, short stature, an erythematous photosensitive malar rash, and increased cancer predisposition. Diagnostically, a hallmark feature is the presence of increased sister chromatid exchanges (SCEs) on cytogenetic testing. Here, we describe biallelic mutations in TOP3A in ten individuals with prenatal-onset growth restriction and microcephaly. TOP3A encodes topoisomerase III alpha (TopIIIα), which binds to BLM as part of the BTRR complex, and promotes dissolution of double Holliday junctions arising during homologous recombination. We also identify a homozygous truncating variant in RMI1, which encodes another component of the BTRR complex, in two individuals with microcephalic dwarfism. The TOP3A mutations substantially reduce cellular levels of TopIIIα, and consequently subjects’ cells demonstrate elevated rates of SCE. Unresolved DNA recombination and/or replication intermediates persist into mitosis, leading to chromosome segregation defects and genome instability that most likely explain the growth restriction seen in these subjects and in Bloom syndrome. Clinical features of mitochondrial dysfunction are evident in several individuals with biallelic TOP3A mutations, consistent with the recently reported additional function of TopIIIα in mitochondrial DNA decatenation. In summary, our findings establish TOP3A mutations as an additional cause of prenatal-onset short stature with increased cytogenetic SCEs and implicate the decatenation activity of the BTRR complex in their pathogenesis.

Bloom syndrome, caused by biallelic mutations in BLM, is characterized by prenatal-onset growth deficiency, short stature, an erythematous photosensitive malar rash, and increased cancer predisposition. Diagnostically, a hallmark feature is the presence of increased sister chromatid exchanges (SCEs) on cytogenetic testing. Here, we describe biallelic mutations in TOP3A in ten individuals with prenatal-onset growth restriction and microcephaly. TOP3A encodes topoisomerase III alpha (TopIII alpha), which binds to BLM as part of the BTRR complex, and promotes dissolution of double Holliday junctions arising during homologous recombination. We also identify a homozygous truncating variant in RMI1, which encodes another component of the BTRR complex, in two individuals with microcephalic dwarfism. The TOP3A mutations substantially reduce cellular levels of TopIII alpha, and consequently subjects' cells demonstrate elevated rates of SCE. Unresolved DNA recombination and/or replication intermediates persist into mitosis, leading to chromosome segregation defects and genome instability that most likely explain the growth restriction seen in these subjects and in Bloom syndrome. Clinical features of mitochondrial dysfunction are evident in several individuals with biallelic TOP3A mutations, consistent with the recently reported additional function of TopIII alpha in mitochondrial DNA decatenation. In summary, our findings establish TOP3A mutations as an additional cause of prenatal-onset short stature with increased cytogenetic SCEs and implicate the decatenation activity of the BTRR complex in their pathogenesis.

RecQ family helicases and topoisomerase 3 enzymes form evolutionary conserved complexes that play essential functions in DNA replication, recombination, and repair, and in vitro, show coordinate activities on model recombination and replication intermediates. Malfunctioning of these complexes in humans is associated with genomic instability and cancer-prone syndromes. Although both RecQ-like and topoisomerase 3 enzymes are present in archaea, only a few of them have been studied, and no information about their functional interaction is available. We tested the combined activities of the RecQ-like helicase, Hel112, and the topoisomerase 3, SsTop3, from the thermophilic archaeon Sulfolobus solfataricus. Hel112 showed coordinate DNA unwinding and annealing activities, a feature shared by eukaryotic RecQ homologs, which resulted in processing of synthetic Holliday junctions and stabilization of model replication forks. SsTop3 catalyzed DNA relaxation and annealing. When assayed in combination, SsTop3 inhibited the Hel112 helicase activity on Holliday junctions and stimulated formation and stabilization of such structures. In contrast, Hel112 did not affect the SsTop3 DNA relaxation activity. RecQ-topoisomerase 3 complexes show structural similarity with the thermophile-specific enzyme reverse gyrase, which catalyzes positive supercoiling of DNA and was suggested to play a role in genome stability at high temperature. Despite such similarity and the high temperature of reaction, the SsTop3-Hel112 complex does not induce positive supercoiling and is thus likely to play different roles. We propose that the interplay between Hel112 and SsTop3 might regulate the equilibrium between recombination and anti-recombination activities at replication forks.

Ultrafine anaphase bridges (UFBs) are thin DNA threads linking the separating sister chromatids in the anaphase of mitosis. UFBs are thought to form when topological DNA entanglements between two chromatids are not resolved prior to anaphase onset. In contrast to other markers of defective chromosome segregation, UFBs cannot be detected by direct staining of the DNA, but instead can be detected using immunofluorescence-based approaches. Due to the fact that they are short-lived and fragile in nature, UFBs can be challenging to detect. In this chapter, we describe methods that have been optimized for successful detection of UFBs. We also provide guidelines for the optimization of UFBs detection depending on the antibody and the cell line to be used.

Ultrafine anaphase bridges (UFBs) are thin DNA threads linking the separating sister chromatids in the anaphase of mitosis. UFBs are thought to form when topological DNA entanglements between two chromatids are not resolved prior to anaphase onset. In contrast to other markers of defective chromosome segregation, UFBs cannot be detected by direct staining of the DNA, but instead can be detected using immunofluorescence-based approaches. Due to the fact that they are short-lived and fragile in nature, UFBs can be challenging to detect. In this chapter, we describe methods that have been optimized for successful detection of UFBs. We also provide guidelines for the optimization of UFBs detection depending on the antibody and the cell line to be used.

PICH is a DNA translocase required for the maintenance of chromosome stability in human cells. Recent data indicate that PICH co-operates with topoisomerase IIα to suppress pathological chromosome missegregation through promoting the resolution of ultra-fine anaphase bridges (UFBs). Here, we identify the BEN domain-containing protein 3 (BEND3) as an interaction partner of PICH in human cells in mitosis. We have purified full length PICH and BEND3 and shown that they exhibit a functional biochemical interaction in vitro. We demonstrate that the PICH–BEND3 interaction occurs via a novel interface between a TPR domain in PICH and a BEN domain in BEND3, and have determined the crystal structure of this TPR–BEN complex at 2.2 Å resolution. Based on the structure, we identified amino acids important for the TPR–BEN domain interaction, and for the functional interaction of the full-length proteins. Our data reveal a proposed new function for BEND3 in association with PICH, and the first example of a specific protein–protein interaction mediated by a BEN domain.

Repair of DNA double strand breaks via homologous recombination can produce double Holliday junctions (dHJs) that require enzymatic separation. Topoisomerase IIIa (TopIIIa) together with RMI1 disentangles the final hemicatenane intermediate obtained once dHJs have converged. How binding of RMI1 to TopIIIa influences it to behave as a hemicatenane dissolvase rather than as an enzyme that relaxes DNA topology is unknown. Here we present the crystal structure of human TopIIIa complexed to the first oligonucleotide binding domain (OB fold) of RMI1. TopIII assumes a toroidal type 1A topoisomerase fold. RMI1 attaches to the edge of the gate in TopIIIa through which DNA passes. RMI1 projects a 23 residue loop into the TopIIIa gate thereby influencing the dynamics of its opening and closing. Our results provide a mechanistic rationale for how RMI1 stabilizes TopIIIa gate opening to enable dissolution and illustrate how binding partners modulate topoisomerase function.