The mechanisms through which environmental and dietary factors modulate DNA repair are still unclear but may include dysregulation of gene expression due to altered epigenetic markings. In a mouse ...model, we investigated the effect of maternal folate depletion during pregnancy and lactation, and high‐fat feeding from weaning, on base excision repair (BER) and DNA methylation and expression of selected BER‐related genes in the brain of adult offspring. While folate depletion did not affect BER activity of the mothers, BER increased in the offspring at weaning (P=0.052). In the long term, as observed in 6‐mo‐old offspring, the double insult, i.e., maternal low‐folate supply and high‐fat feeding from weaning, decreased BER activity significantly in the cortex, cerebellum, hippocampus, and subcortical regions (P <0.017). This fall in BER activity was associated with small changes in methylation or expression of BER‐related genes. Maternal folate depletion led to slightly increased oxidative DNA damage levels in subcortical regions of adult offspring, which may increase sensitivity to oxidative stress and predispose to neurological disorders. In summary, our data suggest that low‐folate supply during early life may leave an epigenetic mark that can predispose the offspring to further dietary insults, causing adverse effects during adult life.—Langie, S. A. S., Achterfeldt, S., Gorniak, J. P., Halley‐Hogg, K. J. A., Oxley, D., van Schooten, F. J., Godschalk, R. W. L., McKay, J. A., Mathers, J. C., Maternal folate depletion and high‐fat feeding from weaning affects DNA methylation and DNA repair in brain of adult offspring. FASEBJ. 27, 3323‐3334 (2013). www.fasebj.org
Molecular profiling has led to identification of subtypes of diffuse large B-cell lymphomas (DLBCLs) differing in terms of oncogenic signaling and metabolic programs. The OxPhos-DLBCL subtype is ...characterized by enhanced mitochondrial oxidative phosphorylation. As increased oxidative metabolism leads to overproduction of potentially toxic reactive oxygen species (ROS), we sought to identify mechanisms responsible for adaptation of OxPhos cells to these conditions. Herein, we describe a mechanism involving the FOXO1-TXN-p300 redox-dependent circuit protecting OxPhos-DLBCL cells from ROS toxicity. We identify a BCL6-dependent transcriptional mechanism leading to relative TXN overexpression in OxPhos cells. We found that OxPhos cells lacking TXN were uniformly more sensitive to ROS and doxorubicin than control cells. Consistent with this, the overall survival of patients with high TXN mRNA expression, treated with doxorubicin-containing regimens, is significantly shorter than of those with low TXN mRNA expression. TXN overexpression curtails p300-mediated FOXO1 acetylation and its nuclear translocation in response to oxidative stress, thus attenuating FOXO1 transcriptional activity toward genes involved in apoptosis and cell cycle inhibition. We also demonstrate that FOXO1 knockdown in cells with silenced TXN expression markedly reduces ROS-induced apoptosis, indicating that FOXO1 is the major sensor and effector of oxidative stress in OxPhos-DLBCLs. These data highlight dynamic, context-dependent modulation of FOXO1 tumor-suppressor functions via acetylation and reveal potentially targetable vulnerabilities in these DLBCLs.
We consider time domain (TD) modelling of diffraction of a signal, caused by 2D conducting convex objects for soft polarization case. Two models of the amplitude term of the time domain convex ...obstacle diffraction coefficient are proposed and compared. One model is derived using an analytical-numerical method and the other is obtained in a purely analytical way. Both methods use uniform geometrical theory of diffraction (UTD) formulated in the frequency domain (FD). The models are used to examine an ultrawideband (UWB) pulse distortion. The accuracy and calculation complexity of both models are compared. The slope term of the convex obstacle diffraction coefficient is also considered, for the case when slope diffraction is not negligible. The UWB pulse distortion caused by overall convex obstacle diffraction is also analysed.
We present a visually-grounded language understanding model based on a study of how people verbally describe objects in scenes. The emphasis of the model is on the combination of individual word ...meanings to produce meanings for complex referring expressions. The model has been implemented, and it is able to understand a broad range of spatial referring expressions. We describe our implementation of word level visually-grounded semantics and their embedding in a compositional parsing framework. The implemented system selects the correct referents in response to natural language expressions for a large percentage of test cases. In an analysis of the system's successes and failures we reveal how visual context influences the semantics of utterances and propose future extensions to the model that take such context into account.
Base excision repair (BER) may become less effective with ageing resulting in accumulation of DNA lesions, genome instability and altered gene expression that contribute to age-related degenerative ...diseases. The brain is particularly vulnerable to the accumulation of DNA lesions; hence, proper functioning of DNA repair mechanisms is important for neuronal survival. Although the mechanism of age-related decline in DNA repair capacity is unknown, growing evidence suggests that epigenetic events (e.g., DNA methylation) contribute to the ageing process and may be functionally important through the regulation of the expression of DNA repair genes. We hypothesize that epigenetic mechanisms are involved in mediating the age-related decline in BER in the brain. Brains from male mice were isolated at 3-32 months of age. Pyrosequencing analyses revealed significantly increased
methylation with ageing, which correlated inversely with
expression. The reduced
expression correlated with enhanced expression of methyl-CpG binding protein 2 and ten-eleven translocation enzyme 2. A significant inverse correlation between
methylation at CpG-site2 and expression was also observed. BER activity was significantly reduced and associated with increased 8-oxo-7,8-dihydro-2'-deoxyguanosine levels. These data indicate that
and
expression can be epigenetically regulated, which may mediate the effects of ageing on DNA repair in the brain.
DNA repair mechanisms are important for genome stability and to prevent accumulation of DNA damage, which contributes to cellular ageing and cancer development. Study of these physiological processes ...requires robust and practical assays to quantify DNA repair capacity. The in vitro comet-based assay is a simple, yet reliable, assay for measurement of DNA repair and has been modified recently to quantify DNA incision activity in mouse brain and liver. In this study, we applied this assay to assess DNA incision activity in other mouse tissues, i.e. lung and colon, and found that high, non-specific nuclease activity was a problem when measuring DNA incision activity, especially in the colon. We tested the utility of multiple optimisation steps including addition of aphidicolin, ATP and polyAT and used multiple wash steps, which resulted in modest improvements in performance of the assay. Washing the tissues before protein extraction and decreasing the protein concentration in the assay were the most effective steps in reducing non-specific nuclease activity. Using the comet-based assay with these further modifications, we found that base excision repair incision activity changed with age differently in each tissue. This study shows that non-specific nuclease activity in the comet-based assay for DNA repair is more pronounced in some tissues than others so care should be taken to optimise the protocol when applying the assay to a new tissue. Our data suggest the importance of using control cells (noRo cells incubated with extract) in the assay to assess for non-specific nuclease activity. In conclusion, the comet-based DNA repair assay can be easily adapted to study a range of mammalian tissues.
The bacterial BcsA-B cellulose synthase synthesizes cellulose II when immobilized on nickel surfaces. To explore how lignin interacts with cellulose, lignin was polymerized either during or after ...cellulose formation from surface immobilized BcsA-B, leading to significant alterations in cellulose and lignin morphology. To facilitate lignin detection, polymerized coniferyl alcohol monolignols were detected by lignin autofluorescence. This compound was previously demonstrated as a suitable lignin monolignol exhibiting autofluorescence that enables lignin detection even at low concentrations. Cellulose and lignin coated nickel surfaces were studied under confocal microscopy, as well as by atomic force microscopy and X-ray diffractometry (XRD). As a consequence of simultaneous lignin and cellulose deposition on the surface, cellulose microfibril morphology was altered. XRD data indicated that cellulose crystal size was significantly decreased by polymerized lignin incorporation, suggesting that simultaneous lignin polymerization prevents the proper assembly of cellulose microfibrils. In contrast, polymerizing lignin after cellulose synthesis yielded a cellulose that was very similar in character to control (lignin-free) samples in terms of crystal morphology.
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