Complexes containing a pair of structural maintenance of chromosomes (SMC) family proteins are fundamental for the three-dimensional (3D) organization of genomes in all domains of life. The ...eukaryotic SMC complexes cohesin and condensin are thought to fold interphase and mitotic chromosomes, respectively, into large loop domains, although the underlying molecular mechanisms have remained unknown. We used cryo-EM to investigate the nucleotide-driven reaction cycle of condensin from the budding yeast Saccharomyces cerevisiae. Our structures of the five-subunit condensin holo complex at different functional stages suggest that ATP binding induces the transition of the SMC coiled coils from a folded-rod conformation into a more open architecture. ATP binding simultaneously triggers the exchange of the two HEAT-repeat subunits bound to the SMC ATPase head domains. We propose that these steps result in the interconversion of DNA-binding sites in the catalytic core of condensin, forming the basis of the DNA translocation and loop-extrusion activities.
Structural maintenance of chromosomes (SMC) protein complexes structure genomes by extruding DNA loops, but the molecular mechanism that underlies their activity has remained unknown. We show that ...the active condensin complex entraps the bases of a DNA loop transiently in two separate chambers. Single-molecule imaging and cryo-electron microscopy suggest a putative power-stroke movement at the first chamber that feeds DNA into the SMC-kleisin ring upon adenosine triphosphate binding, whereas the second chamber holds on upstream of the same DNA double helix. Unlocking the strict separation of "motor" and "anchor" chambers turns condensin from a one-sided into a bidirectional DNA loop extruder. We conclude that the orientation of two topologically bound DNA segments during the SMC reaction cycle determines the directionality of DNA loop extrusion.
•Protein complexes of the SMC family organize chromosomes by extruding large DNA loops.•SMC-mediated loop extrusion presumably requires DNA anchor and motor elements.•Changes in coiled-coil ...conformations might appose distant DNA binding sites during DNA translocation.
Structural Maintenance of Chromosomes (SMC) protein complexes play key roles in the three-dimensional organization of genomes in all kingdoms of life. Recent insights from chromosome contact mapping experiments and single-molecule imaging assays suggest that these complexes achieve distinct cellular functions by extruding large loops of DNA while they move along the chromatin fiber. In this short review, we summarize recent insights into the molecular architecture of these unconventional DNA motor complexes, their interaction with their DNA substrates, and the remarkable dynamic changes they can undergo during their ATPase reaction cycle.
Faced with changes related to climatic hazards or market variability, farmers deploy a variety of strategies to stabilize farm economic performances and reduce risk. One of the challenges faced by ...agricultural systems is how to reduce their sensitivity to these disturbances and maintain a certain level of production of goods and services. If diversity in crop and livestock activities in a farm has been shown to answer this challenge, at a higher scale, the growth of diversity and its benefits remain unclear. Using biotechnical models of existing farms within the territory of the Vallées de Duyes in the South of France, we propose to simulate various territorial configurations based on the assumption of diversity at farm and territorial scales and assess their expected sustainable properties. Based on the actual configuration of the referenced territory and composed of a set of specialized and mixed farms, two contrasted configurations are tested: from one side, a territory composed of specialized farms and, from the other side, a territory composed of mixed farms. The intrinsic diversity of individual farms impacts their performance and reveals that the resistance to economic shock varies according to the dependence on inputs and the use of rangelands. If mixed farms exhibit high values of diversity indicators for both land use and product provision, they also present high values for the majority of sustainable properties. At a higher scale, the specialized configuration shows the highest resistance to economic shock, but economic performances are lower than the referenced and specialized configurations. Here, we explore for the first time how several types of diversity indicators, both built within and between farms, could affect a set of sustainable properties of farms and territories. These new insights lead to a better understanding of how to balance performance at several scales and design sustainable Mediterranean farming systems.
This article explores the issues surrounding the agroecological transition in the European wine industry, focusing on reducing pesticide use, developing organic certification and using genetic ...research in relation to resistant grape varieties. The study distinguishes between stakeholders from the wine industry, institutions and the agricultural research sector. The findings consistently identify the agroecological transition as a priority, particularly in terms of pesticide reduction. However, variations exist in the views of the surveyed stakeholders. French and Portuguese stakeholders emphasise the role of market and societal pressures as drivers of the transition, while Italian producers do not. Professionals in France and Portugal express doubts about achieving pesticide reduction through changes in practices, while others stress the importance of regulatory constraints. The research also highlights industry challenges such as decreased consumption due to health awareness and the need for social responsibility. Resistant grape varieties are seen as a viable solution, especially for the development of organic production, but market acceptability remains a significant hurdle. The study sheds light on stakeholder perspectives and challenges, thus contributing to a better understanding of priorities in the European wine industry’s pursuit of sustainable practices.
Complex incubation strategies have evolved to solve the trade-off between parent survival and care for their eggs with often brief departures (recesses) that maximize egg survival, and infrequent ...extended recesses maximizing adult condition. Here we examined incubation behaviour of sanderlings (
), a species that exhibits both biparental and uniparental incubation behaviour. During 11 breeding seasons in Greenland, we have quantified incubation variability with thermologgers placed in nests. We estimated the impact of environmental conditions and individual characteristics on the occurrence and the duration of recesses. We found that extended recesses are a unique feature of uniparentals, and their frequency and duration increased in colder temperatures. The relationship was mediated by body condition, with individuals in poor condition performing longer extended recesses in colder temperatures. This suggests that extended recesses may represent a shift towards self-maintenance at the expense of the egg care, allowing birds to continue incubating under unfavourable conditions. Our study illustrates how extended recesses may be a key breeding strategy to overcome high energetic costs associated with incubation. Quantifying such behavioural flexibility paves the way for tracking future behavioural responses of individuals in the face of changing environments.
To compare environmental and culture-derived microbial communities, we performed 16S metabarcoding of uncultured samples and their culture-derived bacterial lawns. Microbial communities were obtained ...from freshwater river samples representative of an anthropization gradient along a river stream. Their culture-derived bacterial lawns were obtained by growing aliquots of the samples on a broad range medium and on two different semi-selective media. The V3–V4 16S rRNA region was amplified and sequenced. The bacterial diversity of water samples decreased from the upper to lower stream sampling sites and, as expected, these differences were mostly suppressed by the culture step. Overall, the diversity of cultured-derived bacterial communities reflected selectivity of each tested medium. Comparison of treatments indicated that the culture selected both detected and rare undetected environmental species. Accurate detection of rare environmental bacteria of the Pectobacterium genus by 16S metabarcoding of the culture lawn was demonstrated. Interestingly, for abundant taxa, such as those of the Pseudomonas genus, the culture/environment ratio varied between sampled sites, indicating the difficulty of comparing cultured-derived taxa abundance between environmental sites. Finally, our study also highlighted media specificity and complementarity: bacterial communities grown on the two selective media, while selecting a small set of specific species, were mostly a subset of the bacterial community observed on the broad range medium.
Chaperone synthesis in response to proteotoxic stress is dependent on a family of transcription factors named heat shock factors (HSFs). The two main factors in this family, HSF1 and HSF2, are ...co-expressed in numerous tissues where they can interact and form heterotrimers in response to proteasome inhibition. HSF1 and HSF2 exhibit two alternative splicing isoforms, called α and β, which contribute to additional complexity in HSF transcriptional regulation, but remain poorly examined in the literature. In this work, we studied the transcriptional activity of HSF1 and HSF2 splicing isoforms transfected into immortalized Mouse Embryonic Fibroblasts (iMEFs) deleted for both Hsf1 and Hsf2, under normal conditions and after proteasome inhibition. We found that HSF1α is significantly more active than the β isoform after exposure to the proteasome inhibitor MG132. Furthermore, we clearly established that, while HSF2 had no transcriptional activity by itself, short β isoform of HSF2 exerts a negative role on HSF1β-dependent transactivation. To further assess the impact of HSF2β inhibition on HSF1 activity, we developed a mathematical modelling approach which revealed that the balance between each HSF isoform in the cell regulated the strength of the transcriptional response. Moreover, we found that cellular stress such as proteasome inhibition could regulate the splicing of Hsf2 mRNA. All together, our results suggest that relative amounts of each HSF1 and HSF2 isoforms quantitatively determine the cellular level of the proteotoxic stress response.
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Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
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