Lens epithelium-derived growth factor splice variant of 75 kDa (LEDGF/p75) plays an important role in cancer, but its DNA-damage repair (DDR)-related implications are still not completely understood. ...Different LEDGF model cell lines were generated: a complete knock-out of LEDGF (KO) and re-expression of LEDGF/p75 or LEDGF/p52 using CRISPR/Cas9 technology. Their proliferation and migration capacity as well as their chemosensitivity were determined, which was followed by investigation of the DDR signaling pathways by Western blot and immunofluorescence. LEDGF-deficient cells exhibited a decreased proliferation and migration as well as an increased sensitivity toward etoposide. Moreover, LEDGF-depleted cells showed a significant reduction in the recruitment of downstream DDR-related proteins such as replication protein A 32 kDa subunit (RPA32) after exposure to etoposide. The re-expression of LEDGF/p75 rescued all knock-out effects. Surprisingly, untreated LEDGF KO cells showed an increased amount of DNA fragmentation combined with an increased formation of γH2AX and BRCA1. In contrast, the protein levels of ubiquitin-conjugating enzyme UBC13 and nuclear proteasome activator PA28γ were substantially reduced upon LEDGF KO. This study provides for the first time an insight that LEDGF is not only involved in the recruitment of CtIP but has also an effect on the ubiquitin-dependent regulation of DDR signaling molecules and highlights the role of LEDGF/p75 in homology-directed DNA repair.
Lemna minor
L., a widely used model plant for toxicity tests has raised interest for its application to phytoremediation due to its rapid growth and ubiquitous occurrence. In rural areas, the ...pollution of water bodies with heavy metals and agrochemicals poses a problem to surface water quality. Among problematic compounds, heavy metals (copper) and pesticides are frequently found in water bodies. To establish duckweed as a potential plant for phytoremediation, enzymatic and antioxidative stress responses of
Lemna minor
during exposure to copper and a chloroacetamide herbicide were investigated in laboratory studies. The present study aimed at evaluating growth and the antioxidative and glutathione-dependent enzyme activity of
Lemna
plants and its performance in a scenario for phytoremediation of copper and a chloroacetamide herbicide.
Lemna minor
was grown in Steinberg medium under controlled conditions. Plants were treated with CuSO
4
(ion conc. 50 and 100 μg/L) and pethoxamide (1.25 and 2.5 μg/L). Measurements following published methods focused on plant growth, oxidative stress, and basic detoxification enzymes. Duckweed proved to survive treatment with the respective concentrations of both pollutants very well. Its growth was inhibited scarcely, and no visible symptoms occurred. On the cellular basis, accumulation of O
2
−
and H
2
O
2
were detected, as well as stress reactions of antioxidative enzymes. Duckweed detoxification potential for organic pollutants was high and increased significantly with incubation. Pethoxamide was found to be conjugated with glutathione. Copper was accumulated in the fronds at high levels, and transient oxidative defense reactions were triggered. This work confirms the significance of
L. minor
for the removal of copper from water and the conjugation of the selective herbicide pethoxamide. Both organic and inorganic xenobiotics induced different trends of enzymatic and antioxidative stress response. The strong increase of stress responses following copper exposure is well known as oxidative burst, which is probably different from the much more long-lasting responses found in plants exposed to pethoxamide.
Lemna
sp. might be used as a tool for phytoremediation of low-level contamination with metals and organic xenobiotics, however the authors recommend a more detailed analysis of the development of the oxidative burst following copper exposure and of the enzymatic metabolism of pethoxamide in order to elucidate the extent of its removal from water.
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•Mangroves have higher soil OC burial rate, while salt marshes have higher OC stock.•OC from newly established wetland plants is stored unprotected as particulate ...OC.•Microbially-transformed OC from previous plant community is more mineral-associated.•Oxidizing rhizosphere enhances the association of recent-plant OC with reactive iron.•The formation of reactive iron-associated OC may be inhibited in R. mangle habitats.
The global warming-driven poleward expansion of mangrove habitats (e.g., Avicennia germinans and Rhizophora mangle) into temperate salt marshes (e.g., Spartina alterniflora and Juncus roemerianus) has been shown to alter coastal soil organic carbon (SOC) storage. However, the taxa-specific consequences of this vegetation shift on the origin and size of SOC sub-fractions (particulate OC (POC); mineral-associated OC (MAOC); and reactive iron-associated OC (FeR-MAOC)) remain largely unexplored. In this study, we used a particle size-based SOC fractionation method to compare quantity and δ13C composition of bulk and each SOC sub-fractions in soil cores collected from Apalachicola Bay barrier islands in Florida, USA, the highest latitude where monospecific communities of all four aforementioned plants co-occur. Depth-dependent variation of bulk soil δ13C clearly showed the global warming-driven replacement of S. alterniflora by mangroves, as well as reciprocal substitutions of S. alterniflora and J. roemerianus, probably driven by changes in wetland elevation. Higher OC burial rates in mangrove habitats suggested that mangrove soils were principally developed by particle deposition. In contrast, comparatively lower OC burial rates but higher OC stocks in salt marsh habitats illustrated subsurface OC input from salt marsh roots. POC was primarily derived from contemporary plant detritus; its concentration was higher in salt marsh habitats (58.8 ± 9.0 % of SOC) relative to mangroves (38.4 ± 6.0 % of SOC). In contrast, MAOC content did not vary across plant habitats (53.5 ± 10.9 % of SOC), and principally originated from microbially-transformed OC and pre-existing plants. FeR-MAOC was essentially absent in R. mangle soils (2.9 ± 3.6 % of SOC) while representing a minor fraction of MAOC in three other plant habitats (7.8 ± 7.0 % of SOC). The δ13C of FeR-MAOC was more like the present-day surface plants, highlighting the in situ FeR-MAOC formation in their active oxidizing rhizospheres.
Reactive iron (FeR) plays an important role in the preservation of organic carbon (OC) in coastal sediments, yet changes in the OC bound to FeR (OC-FeR), during transport and deposition, remain ...poorly understood. The main goal of this work is to investigate the variation of the age and composition of OC-FeR from estuarine suspended particulate matter (SPM) to coastal sediments, to further understand the role of FeR in the preservation of terrestrial OC exported from large rivers into marginal seas. We examined OC and its carbon isotopic composition (Δ14Cbulk, δ13Cbulk), specific surface area (SSA), grain size composition, lignin phenols, FeR, Mössbauer spectroscopy, and isotopic signatures of OC-FeR (Δ14COC-FeR, δ13COC-FeR) in SPM and surface sediments of the Changjiang Estuary. Particulate OC (POC) and FeR concentrations in SPM are significantly higher than in surface sediments, with no significant differences between surface- and bottom-water SPM. This indicates that loss of OC and FeR largely occurs at the sediment–water interface due in part, to rapid Fe cycling. The percentage of OC-FeR (fOC-FeR) in SPM (6.6 ± 1.9%) is similar to that in mobile-mud sediment (8.8 ± 1.8%). There are no significant differences in OC-FeR content (p > 0.05) from SPM to mobile-mud sediments, but non-OC-FeR largely decreases, suggesting that terrestrial OC-FeR has greater stability compared to terrestrial non-OC-FeR. Both δ13COC-FeR and Δ14COC-FeR are lower than bulk OC, indicating that FeR is mainly associated with pre-aged soil OC of terrestrial plant origin, especially in estuarine SPM and mobile-mud sediments. Taken together, binding with FeR is a potential long-term protection mechanism for terrestrial OC. Both Δ14Cbulk and Δ14COC-FeR decrease with an increase in the ratio of hematite to (super)paramagnetic Fe3+, indicating that high-crystallinity iron oxide is largely associated with pre-aged terrestrial OC, and there is a potential joint maturation mechanism between FeR and its associated OC. Based on literature comparisons of soils, estuarine SPM, and marine sediments, OC-FeR associations are controlled mainly by sedimentary regimes, FeR compositions, and OC sources. This work supports the notion that FeR plays an important role in the stabilization and transport of river-derived terrestrial OC.
The derivation of atomic polarizabilities for polarizable force field development has been a long-standing problem. Atomic polarizabilities were often refined manually starting from tabulated values, ...rendering an automated assignment of parameters difficult and hampering reproducibility and transferability of the obtained values. To overcome this, we trained both a linear increment scheme and a multilayer perceptron neural network on a large number of high-quality quantum mechanical atomic polarizabilities and partial atomic charges, where only the type of each atom and its connectivity were used as input. The predicted atomic polarizabilities and charges had average errors of 0.023 Å3 and 0.019 e using the neural net and 0.063 Å3 and 0.069 e using the simple increment scheme. As the algorithm relies only on the connectivities of the atoms within a molecule, thus omitting dependencies on the three-dimensional conformation, the approach naturally assigns like charges and polarizabilities to symmetrical groups. Accordingly, a convenient utility is presented for generating the partial atomic charges and atomic polarizabilities for organic molecules as needed in polarizable force field development.
The nuclear Overhauser effect (NOE) is a powerful tool in molecular structure elucidation, combining the subtle chemical shift of NMR and three-dimensional information independent of chemical ...connectivity. Its usage for intermolecular studies, however, is fundamentally limited by an unspecific long-ranged interaction behavior. This joint experimental and computational work shows that proper selection of interacting isotopes can overcome these limitations: Isotopes with strongly differing gyromagnetic ratios give rise to short-ranged intermolecular NOEs. In this light, existing NOE experiments need to be re-evaluated and future ones can be designed accordingly. Thus, a new chapter on intermolecular structure elucidation is opened.
In times of rising antibiotic resistances, there is a high need for fast, sensitive and specific methods to determine antibiotic susceptibilities of bacterial pathogens. Here, we present an ...integrated microfluidic device in which bacteria from diluted suspensions are captured in well-defined regions using on-chip dielectrophoresis and further analyzed in a label-free and non-destructive manner using Raman spectroscopy. Minimal sample preparation and automated sample processing ensure safe handling of infectious material with minimal hands-on time for the operator. Clinical applicability of the presented device is demonstrated by antibiotic susceptibility testing of Escherichia coli towards the commonly prescribed second generation fluoroquinolone ciprofloxacin. Ciprofloxacin resistant E. coli were differentiated from sensitive E. coli with high accuracy within roughly three hours total analysis time paving the way for future point-of-care devices. Spectral changes leading to the discrimination between sensitive and resistant bacteria are in excellent agreement with expected metabolic changes in the bacteria due to the mode of action of the drug. The robustness of the method was confirmed with experiments involving different chip devices with different designs, both electrode as well as microfluidics design, and material. Furthermore, general applicability was demonstrated with different operators over an extended time period of half a year.
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