The Interplay of Cohesin and the Replisome at Processive and Stressed DNA Replication Forks

The cohesin complex facilitates faithful chromosome segregation by pairing the sister chromatids after DNA replication until mitosis. In addition, cohesin contributes to proficient and error-free DNA replication. Replisome progression and establishment of sister chromatid cohesion are intimately intertwined processes. Here, we review how the key factors in DNA replication and cohesion establishment cooperate in unperturbed conditions and during DNA replication stress. We discuss the detailed molecular mechanisms of cohesin recruitment and the entrapment of replicated sister chromatids at the replisome, the subsequent stabilization of sister chromatid cohesion via SMC3 acetylation, as well as the role and regulation of cohesin in the response to DNA replication stress.

MICA/B antibody induces macrophage-mediated immunity against acute myeloid leukemia

Acute myeloid leukemia (AML) is a clonal hematopoietic stem and progenitor cell malignancy characterized by poor clinical outcomes. MICA and MICB (MICA/B) are stress-proteins expressed by cancer cells, and antibody-mediated inhibition of MICA/B shedding represents a novel approach to stimulate immunity against cancers. We found that the MICA/B antibody 7C6 potently inhibits the outgrowth of AML in two models in immunocompetent mice. Macrophages were essential for therapeutic efficacy, and 7C6 triggered antibody-dependent phagocytosis of AML cells. Furthermore, we found that romidepsin, a selective histone deacetylase inhibitor, increased MICB mRNA in AML cells and enabled subsequent stabilization of the translated protein by 7C6. This drug combination substantially increased surface MICA/B expression in a human AML line, pluripotent stem cell-derived AML blasts and leukemia stem cells, as well as primary cells from three untreated AML patients. Human macrophages phagocytosed AML cells following treatment with 7C6 and romidepsin, and the combination therapy lowered leukemia burden in a humanized model of AML. Therefore, inhibition of MICA/B shedding promotes macrophage-driven immunity against AML via Fc receptor signaling and synergizes with an epigenetic regulator. These results provide the rationale for the clinical testing of this innovative immunotherapeutic approach for the treatment of AML.

Trends over time in the risk of adverse outcomes among patients with SARS-CoV-2 infection

ObjectivesWe aimed to describe trends in the incidence of adverse outcomes among patients who tested positive for SARS-CoV-2 between February and September 2020 within a national healthcare system.SettingUS Veterans Affairs national healthcare system.ParticipantsEnrollees in the VA healthcare system who tested positive for SARS-CoV-2 between 2/28/2020 and 9/30/2020 (n=55,952).OutcomesDeath, hospitalization, intensive care unit (ICU) admission and mechanical ventilation within 30 days of testing positive.The incidence of these outcomes was examined among patients infected each month and trends were evaluated using an interrupted time-series analysis.ResultsBetween February and July 2020, during the first wave of the US pandemic, there were marked downward trends in the 30-day incidence of hospitalization (44.2% to 15.8%), ICU admission (20.3% to 5.3%), mechanical ventilation (12.7% to 2.2%), and death (12.5% to 4.4%), with subsequent stabilization between July and September 2020. These trends persisted after adjustment for sociodemographic characteristics, comorbid conditions, and documented symptoms and after additional adjustment for laboratory test results among hospitalized patients, including among subgroups admitted to the ICU and treated with mechanical ventilation. Among hospitalized patients, use of hydroxychloroquine (56.5% to 0%), azithromycin (48.3% to 16.6%) vasopressors (20.6% to 8.7%), and dialysis (11.6% to 3.8%) decreased while use of dexamethasone (3.4% to 53.1%), other corticosteroids (4.9% to 29.0%) and remdesivir (1.7% to 45.4%) increased from February to September.ConclusionsAmong patients who tested positive for SARS-CoV-2 in a large national US healthcare system, risk for a range of adverse outcomes decreased markedly between February and July, with subsequent stabilization from July to September. These trends were not explained by changes in measured baseline patient characteristics.

Generation of stress fibers through myosin-driven reorganization of the actin cortex

Contractile actomyosin bundles, stress fibers, govern key cellular processes including migration, adhesion, and mechanosensing. Stress fibers are thus critical for developmental morphogenesis. The most prominent actomyosin bundles, ventral stress fibers, are generated through coalescence of pre-existing stress fiber precursors. However, whether stress fibers can assemble through other mechanisms has remained elusive. We report that stress fibers can also form without requirement of pre-existing actomyosin bundles. These structures, which we named cortical stress fibers, are embedded in the cell cortex and assemble preferentially underneath the nucleus. In this process, non-muscle myosin II pulses orchestrate the reorganization of cortical actin meshwork into regular bundles, which promote reinforcement of nascent focal adhesions, and subsequent stabilization of the cortical stress fibers. These results identify a new mechanism by which stress fibers can be generated de novo from the actin cortex and establish role for stochastic myosin pulses in the assembly of functional actomyosin bundles.

Enhancing catalytic potential of gold nanoparticles by linear and cross-linked polyurethane blending

This work describes the synthesis of gold nanoparticles (AuNPs) and their subsequent stabilization using a water-borne polyurethane matrix of micro-particles (Au/PU).

Stabilization and Incipient Carbonization of Electrospun Polyacrylonitrile Nanofibers Fixated on Aluminum Substrates

Polyacrylonitrile (PAN) nanofibers, prepared by electrospinning, are often used as a precursor for carbon nanofibers. The thermal carbonization process necessitates a preceding oxidative stabilization, which is usually performed thermally, i.e., by carefully heating the electrospun nanofibers in an oven. One of the typical problems occurring during this process is a strong deformation of the fiber morphologies—the fibers become thicker and shorter, and show partly undesired conglutinations. This problem can be solved by stretching the nanofiber mat during thermal treatment, which, on the other hand, can lead to breakage of the nanofiber mat. In a previous study, we have shown that the electrospinning of PAN on aluminum foils and the subsequent stabilization of this substrate is a simple method for retaining the fiber morphology without breaking the nanofiber mat. Here, we report on the impact of different aluminum foils on the physical and chemical properties of stabilized PAN nanofibers mats, and on the following incipient carbonization process at a temperature of max. 600 °C, i.e., below the melting temperature of aluminum.

Generation of stress fibers through myosin-driven re-organization of the actin cortex

SummaryContractile actomyosin bundles, stress fibers, govern key cellular processes including migration, adhesion, and mechanosensing. Stress fibers are thus critical for developmental morphogenesis. The most prominent actomyosin bundles, ventral stress fibers, are generated through coalescence of pre-existing stress fiber precursors. However, whether stress fibers can assemble through other mechanisms has remained elusive. We report that stress fibers can also form without requirement of pre-existing actomyosin bundles. These structures, which we named cortical stress fibers, are embedded in the cell cortex and assemble preferentially underneath the nucleus. In this process, non-muscle myosin II pulses orchestrate the reorganization of cortical actin meshwork into regular bundles, which promote reinforcement of nascent focal adhesions, and subsequent stabilization of the cortical stress fibers. These results identify a new mechanism by which stress fibers can be generated de novo from the actin cortex, and establish role for stochastic myosin pulses in the assembly of functional actomyosin bundles.

INTERACTION OF α-CARBANIONS OF LITHIUM ACYLATES WITH 1,2-DIBROMOALKANES

We have studied the interaction of α-carbanions of lithium acylates with 1,2-dibromoalkanes with different length of the carbon chain in order to establish the direction of the reaction. Interaction of α-carbanions of lithium acylates obtained by metallation of acetic, butyric and isobutyric acids with lithium diisopropylamide and 1,2-dibromoalkanes (1,2-dibromohexane, 1,2-dibromoheptane or 1,2-dibromononane) with a molar ratio of reactants equal to 1: 2: 1 in argon atmosphere in tetrahydrofuran under normal conditions (20-25 °C) for 2 h leads to the products of the oxidative coupling of enolate anions: succinic acid, 2,3-diethylsuccinic acid (mixture of diastereomers of meso- and (±) -form in a ratio of ~ 2: 1) and 2,2,3,3-tetramethylsuccinic acid with 10-70% yields. We didn’t observe any products of sequential nucleophilic substitution in reaction. The yields of dicarboxylic acids depend on the structure of the initial α-carbanion of lithium acylate and on the carbon chain length of 1,2-dibromoalkane involved in the reaction. We established that the oxidative coupling proceeds most effectively in the interaction of 1,2-dibromoalkanes with an α-carbanion containing an anionoid center at the secondary α-carbon atom - α-carbanion of lithium butyrate (2,3-diethylsuccinic acid yields are 31-70%). We suggested the most probable anion-radical scheme of the formation of the products of the oxidative coupling of α-carbanions of lithium acylates through electron transfer from the enolate anion to 1,2-dibromoalkane with the generation of its radical anion. The pathways for the formation of primary bromoalkanes (1-bromohexane, 1-bromoheptane, 1-bromononane) and terminal olefins (hexene-1, heptene-1, nonene-1) that are generated from the corresponding 1,2-dibromoalkanes during the elimination of their radical anions with the loss of the bromine anion and the subsequent stabilization of 1-bromoalkyl radicals by abstraction of the hydrogen atom from the solvent, or by bromine elimination, are shown.

Biosynthesis, Anti-TB Activity and Degradation of Dyes by Silver Nanoparticles using Fruits Peels

In the present work, waste materials such as pomegranate and orange peels were taken to synthesize nanoparticles by biological method. The method did not involve the use of toxic reducing and capping agents. It uses only the environmentally benign biomolecules for reduction of AgNO3 and subsequent stabilization of silver nanoparticles. The size of pomegranate and orange silver nanoparticles varied from 8-25 nm with nearly spherical morphology as analyzed by XRD and TEM studies. The synthesized nanoparticles were studied for their dye degrading property. Different dyes such as crystal violet, methylene blue, malachite green and Congo red were taken for the study. The results indicated the presence of two diverse mechanism of dye removal. Crystal violet, methylene blue, malachite green was removed by adsorption onto both the nanoparticles, whereas Congo red was reduced by NaBH4 in the presence of catalytic pomegranate silver nanoparticles. Moreover, pomegranate silver nanoparticles have exhibited potent antitubercular activity with MIC value of 6.25 μg/mL and orange silver nanoparticles are moderately active with MIC value of 25 μg/mL. It could be concluded that the pomegranate silver nanoparticles would a promising candidate for drug development and catalysis.