The Smc5/6 complex is required for dissolution of DNA-mediated sister chromatid linkages

Mitotic chromosome segregation requires the removal of physical connections between sister chromatids. In addition to cohesin and topological entrapments, sister chromatid separation can be prevented by the presence of chromosome junctions or ongoing DNA replication. We will collectively refer to them as DNA-mediated linkages. Although this type of structures has been documented in different DNA replication and repair mutants, there is no known essential mechanism ensuring their timely removal before mitosis. Here, we show that the dissolution of these connections is an active process that requires the Smc5/6 complex, together with Mms21, its associated SUMO-ligase. Failure to remove DNA-mediated linkages causes gross chromosome missegregation in anaphase. Moreover, we show that Smc5/6 is capable to dissolve them in metaphase-arrested cells, thus restoring chromosome resolution and segregation. We propose that Smc5/6 has an essential role in the removal of DNA-mediated linkages to prevent chromosome missegregation and aneuploidy

Smc5/6: a link between DNA repair and unidirectional replication?

Of the three structural maintenance of chromosome (SMC) complexes, two directly regulate chromosome dynamics. The third, Smc5/6, functions mainly in homologous recombination and in completing DNA replication. The literature suggests that Smc5/6 coordinates DNA repair, in part through post-translational modification of uncharacterized target proteins that can dictate their subcellular localization, and that Smc5/6 also functions to establish DNA-damage-dependent cohesion. A nucleolar-specific Smc5/6 function has been proposed because Smc5/6 yeast mutants display penetrant phenotypes of ribosomal DNA (rDNA) instability. rDNA repeats are replicated unidirectionally. Here, we propose that unidirectional replication, combined with global Smc5/6 functions, can explain the apparent rDNA specificity

Early and annual projected savings from anti-CGRP monoclonal antibodies in migraine prevention: a cost-benefit analysis in the working-age population

Anti-CGRP monoclonal antibodies; Migraine prevention; Cost-benefitAnticuerpos monoclonales anti-CGRP; Prevención de la migraña; Costo-beneficioAnticossos monoclonals anti-CGRP; Prevenció de la migranya; Cost-beneficiBackground Migraine is one of the main causes of disability worldwide. Anti-CGRP monoclonal antibodies (MAbs) have proven to be safe and efficacious as preventive migraine treatments. However, their use is restricted in many countries due to their apparently high cost. Cost-benefit studies are needed. Objective To study the cost-benefit of anti-CGRP MAbs in working-age patients with migraine. Methods This is a prospective cohort study of consecutive migraine patients treated with anti-CGRP MAbs (erenumab, fremanezumab and galcanezumab) following National reimbursement policy in a specialized headache clinic. Migraine characteristics and the work impact scale (WPAI) were compared between baseline (M0) and after 3 (M3) and 6 months (M6) of treatment. Using WPAI and the municipal average hourly wage, we calculated indirect costs (absenteeism and presenteeism) at each time point. Direct costs (emergency visits, acute medication use) were also analysed. A cost-benefit study was performed considering the different costs and savings of treating with MAbs. Based on these data an annual projection was conducted. Results From 256 treated working-age patients, 148 were employed (89.2% women; mean age 48.0 ± 8.5 years), of which 41.2% (61/148) were responders (> 50% reduction in monthly headache days (MHD)). Statistically significant reductions between M0 and M3/M6 were found in absenteeism (p < 0.001) and presenteeism (p < 0.001). Average savings in indirect costs per patient at M3 were absenteeism 105.4 euros/month and presenteeism 394.3 euros/month, similar for M6. Considering the monthly cost of anti-CGRP MAbs, the cost-benefit analysis showed savings of 159.8 euros per patient at M3, with an annual projected savings of 639.2 euros/patient. Both responders and partial responders (30–50% reduction in MHD) presented a positive cost-benefit balance. The overall savings of the cohort at M3/M6 compensated the negative cost-benefit balance for non-responders (< 30% reduction in MHD). Conclusion Anti-CGRP MAbs have a positive impact in the workforce significantly reducing absenteeism and presenteeism. In Spain, this benefit overcomes the expenses derived from their use already at 3 months and is potentially sustainable at longer term; also in patients who are only partial responders, prompting reconsideration of current reimbursement criteria and motivating the extension of similar cost-benefit studies in other countries

Real-time approaches for characterization of fully and partially scanned canopies in groves

Efficient information management in orchard characterization leads to more efficient agricultural processes. In this brief, a set of computational geometry methods are presented and evaluated for orchard characterization; in particular, for the estimation of canopy volume and shape in groves and orchards using a LiDAR (Light Detection And Ranging) sensor mounted on an agricultural service unit. The proposed approaches were evaluated and validated in the field, showing they are convergent in the estimation process and that they are able to estimate the crown volume for fully scanned canopies in real time; for partially observed tree crowns, accuracy decreases up to 30% (the worst case). The latter is the major contribution of this brief since it implies that the automated service unit does not need to cover all alley-ways for an accurate modeling of the orchard, thus saving valuable resources.The authors would like to thank to CONICYT (Chile): FONDECYT Grant 1140575 and Basal Grant FB0008. Also, this research was partially funded by the Spanish Ministry of Science and Innovation and by the European Union through the FEDER funds (projects Optidosa-AGL2007-66093-C04-03 and Safespray-AGL2010-22304-C04-03)

Exciting Modes due to the Aberration of Gravitational Waves: Measurability for Extreme-Mass-Ratio Inspirals

Gravitational waves from a source moving relative to us can suffer from special-relativistic effects such as aberration. The required velocities for these to be significant are on the order of 1000  km s⁻¹. This value corresponds to the velocity dispersion that one finds in clusters of galaxies. Hence, we expect a large number of gravitational-wave sources to have such effects imprinted in their signals. In particular, the signal from a moving source will have its higher modes excited, i.e., (3,3) and beyond. We derive expressions describing this effect and study its measurability for the specific case of a circular, nonspinning extreme-mass-ratio inspiral. We find that the excitation of higher modes by a peculiar velocity of 1000  km s⁻¹ is detectable for such inspirals with signal-to-noise ratios of ≳20. Using a Fisher matrix analysis, we show that the velocity of the source can be measured to a precision of just a few percent for a signal-to-noise ratio of 100. If the motion of the source is ignored, parameter estimates could be biased, e.g., the estimated masses of the components through a Doppler shift. Conversely, by including this effect in waveform models, we could measure the velocity dispersion of clusters of galaxies at distances inaccessible to light

Rtt107 Phosphorylation Promotes Localisation to DNA Double-Stranded Breaks (DSBs) and Recombinational Repair between Sister Chromatids

Efficient repair of DNA double-stranded breaks (DSB) requires a coordinated response at the site of lesion. Nucleolytic resection commits repair towards homologous recombination, which preferentially occurs between sister chromatids. DSB resection promotes recruitment of the Mec1 checkpoint kinase to the break. Rtt107 is a target of Mec1 and serves as a scaffold during repair. Rtt107 plays an important role during rescue of damaged replication forks, however whether Rtt107 contributes to the repair of DSBs is unknown. Here we show that Rtt107 is recruited to DSBs induced by the HO endonuclease. Rtt107 phosphorylation by Mec1 and its interaction with the Smc5–Smc6 complex are both required for Rtt107 loading to breaks, while Rtt107 regulators Slx4 and Rtt101 are not. We demonstrate that Rtt107 has an effect on the efficiency of sister chromatid recombination (SCR) and propose that its recruitment to DSBs, together with the Smc5–Smc6 complex is important for repair through the SCR pathway

Purified Smc5/6 complex exhibits DNA substrate recognition and compaction

Eukaryotic SMC complexes, cohesin, condensin, and Smc5/6, use ATP hydrolysis to power a plethora of functions requiring organization and restructuring of eukaryotic chromosomes in interphase and during mitosis. The Smc5/6 mechanism of action and its activity on DNA are largely unknown. Here we purified the budding yeast Smc5/6 holocomplex and characterized its core biochemical and biophysical activities. Purified Smc5/6 exhibits DNA-dependent ATP hydrolysis and SUMO E3 ligase activity. We show that Smc5/6 binds DNA topologically with affinity for supercoiled and catenated DNA templates. Employing single-molecule assays to analyze the functional and dynamic characteristics of Smc5/6 bound to DNA, we show that Smc5/6 locks DNA plectonemes and can compact DNA in an ATP-dependent manner. These results demonstrate that the Smc5/6 complex recognizes DNA tertiary structures involving juxtaposed helices and might modulate DNA topology by plectoneme stabilization and local compaction.The work in the Aragon laboratory was supported by a Wellcome Trust Senior Investigator award to L.A. (100955, “Functional dissection of mitotic chromatin”) and the London Institute of Medical Research (LMS), which receives its core funding from the UK Medical Research Council (MC-A652-5PY00). F.M.-H. acknowledges support from the European Research Council (ERC) under the European Union Horizon 2020 Research and Innovation Program (grant agreement 681299). Work in the Moreno-Herrero laboratory was also supported by Spanish Ministry of Economy and Competitiveness grant BFU2017-83794-P (AEI/FEDER, UE to F.M.-H.) and Comunidad de Madrid grants Tec4Bio – S2018/NMT-4443 and NanoBioCancer – Y2018/BIO-4747 (to F.M.-H.). Work in the J.T.-R. lab was supported by grants BFU2015-71308-P and PGC2018-097796-B-I00 from the Ministerio de Ciencia, Innovación y Universidades and grant 2017-SGR-569 from AGAUR-Generalitat de Catalunya. The IRBLLEIDA Institute is part of the CERCA Programme-Generalitat de Catalunya