Direct evidence of electronic ferroelectricity in YbFe2O4 using neutron diffraction and nonlinear spectroscopy

We report the first observation of room temperature spontaneous electric polarization in an electronic ferroelectric material, a YbFe2O4 single crystal. The observation was based on second harmonic generation (SHG), a nonlinear optical process. Tensor analysis of the SHG signal revealed that this material has a polar charge superstructure with Cm symmetry. This result settles the long-term discussion on the uncertainty about electronic ferroelectric properties, including the charge order structure. We present a complete picture of the polar charge ordering of this material via consistent results from two different characterization methods. The SHG signal shows the same temperature dependence as the superlattice signal observed in neutron diffraction experiments. These results prove ferroelectric coupling to electron ordering in YbFe2O4, which results in electronic ferroelectricity which is enabled by the real space ordering of iron cations with different valences. The existence of electronic ferroelectricity holds promise for future electronics technologies where devices run a thousand times faster than frequency of the present CPU (a few gigahertz) embedded in smartphones, etc

Binomial Mitotic Segregation of MYCN-Carrying Double Minutes in Neuroblastoma Illustrates the Role of Randomness in Oncogene Amplification

BACKGROUND: Amplification of the oncogene MYCN in double minutes (DMs) is a common finding in neuroblastoma (NB). Because DMs lack centromeric sequences it has been unclear how NB cells retain and amplify extrachromosomal MYCN copies during tumour development. PRINCIPAL FINDINGS: We show that MYCN-carrying DMs in NB cells translocate from the nuclear interior to the periphery of the condensing chromatin at transition from interphase to prophase and are preferentially located adjacent to the telomere repeat sequences of the chromosomes throughout cell division. However, DM segregation was not affected by disruption of the telosome nucleoprotein complex and DMs readily migrated from human to murine chromatin in human/mouse cell hybrids, indicating that they do not bind to specific positional elements in human chromosomes. Scoring DM copy-numbers in ana/telophase cells revealed that DM segregation could be closely approximated by a binomial random distribution. Colony-forming assay demonstrated a strong growth-advantage for NB cells with high DM (MYCN) copy-numbers, compared to NB cells with lower copy-numbers. In fact, the overall distribution of DMs in growing NB cell populations could be readily reproduced by a mathematical model assuming binomial segregation at cell division combined with a proliferative advantage for cells with high DM copy-numbers. CONCLUSION: Binomial segregation at cell division explains the high degree of MYCN copy-number variability in NB. Our findings also provide a proof-of-principle for oncogene amplification through creation of genetic diversity by random events followed by Darwinian selection

MLN64 Transport to the Late Endosome Is Regulated by Binding to 14-3-3 via a Non-canonical Binding Site

MLN64 is an integral membrane protein localized to the late endosome and plasma membrane that is thought to function as a mediator of cholesterol transport from endosomal membranes to the plasma membrane and/or mitochondria. The protein consists of two distinct domains: an N-terminal membrane-spanning domain that shares homology with the MENTHO protein and a C-terminal steroidogenic acute regulatory protein (StAR)-related lipid transfer (START) domain that binds cholesterol. To further characterize the MLN64 protein, full-length and truncated proteins were overexpressed in cells and the effects on MLN64 trafficking and endosomal morphology were observed. To gain insight into MLN64 function, affinity chromatography and mass spectrometric techniques were used to identify potential MLN64 interacting partners. Of the 15 candidate proteins identified, 14-3-3 was chosen for further characterization. We show that MLN64 interacts with 14-3-3 in vitro as well as in vivo and that the strength of the interaction is dependent on the 14-3-3 isoform. Furthermore, blocking the interaction through the use of a 14-3-3 antagonist or MLN64 mutagenesis delays the trafficking of MLN64 to the late endosome and also results in the dispersal of endocytic vesicles to the cell periphery. Taken together, these studies have determined that MLN64 is a novel 14-3-3 binding protein and indicate that 14-3-3 plays a role in the endosomal trafficking of MLN64. Furthermore, these studies suggest that 14-3-3 may be the link by which MLN64 exerts its effects on the actin-mediated endosome dynamics

De novo fatty-acid synthesis and related pathways as molecular targets for cancer therapy

Enhanced lipid biosynthesis is a characteristic feature of cancer. Deregulated lipogenesis plays an important role in tumour cell survival. These observations suggest that enzymes in the lipid synthesis pathway would be rational therapeutic targets for cancer. To this end, we review the enzymes in de novo fatty-acid synthesis and related pathways

Decreases in the Serum VLDL-TG/Non-VLDL-TG Ratio from Early Stages of Chronic Hepatitis C: Alterations in TG-Rich Lipoprotein Levels

BACKGROUND: The liver secretes very-low-density lipoproteins (VLDLs) and plays a key role in lipid metabolism. Plasma total triglyceride (TG) level variations have been studied in patients with hepatitis C virus (HCV)-related chronic hepatitis (CH-C). However, the results of these studies are variable. A homogenous assay protocol was recently proposed to directly measure the TG content in VLDL (VLDL-TG) and VLDL remnants. METHODOLOGY/PRINCIPAL FINDINGS: Using the assay protocol, we determined serum VLDL-TG levels in 69 fasting patients with biopsy-proven HCV-related chronic liver disease and 50 healthy subjects. Patients were classified into stages F0-F4 using the 5-point Desmet scale. Serum total TG levels in patients with non-cirrhotic (F1-F3) CH-C did not demonstrate significant differences compared with healthy subjects, but serum VLDL-TG levels did demonstrate significant differences. Mean serum VLDL-TG levels tended to decrease with disease progression from F1 to F4 (cirrhosis). Compared with healthy subjects, serum non-VLDL-TG levels significantly increased in patients with stages F2 and F3 CH-C; however, we observed no significant difference in patients with liver cirrhosis. Furthermore, the serum VLDL-TG/non-VLDL-TG ratio, when taken, demonstrated a significant decrease in patients with CH-C from the mildest stage F1 onward. CONCLUSIONS/SIGNIFICANCE: The decrease in serum VLDL-TG levels was attenuated by increase in non-VLDL-TG levels in patients with non-cirrhotic CH-C, resulting in comparable total TG levels. Results of previous studies though variable, were confirmed to have a logical basis. The decrease in the serum VLDL-TG/non-VLDL-TG ratio as early as stage F1 demonstrated TG metabolic alterations in early stages of CH-C for the first time. The involvement of TG metabolism in CH-C pathogenesis has been established in experimental animals, while conventional TG measurements are generally considered as poor indicators of CH-C progression in clinical practice. The serum VLDL-TG/non-VLDL-TG ratio, which focuses on TG metabolic alterations, may be an early indicator of CH-C

Epithelial cell senescence impairs repair process and exacerbates inflammation after airway injury

<p>Abstract</p> <p>Background</p> <p>Genotoxic stress, such as by exposure to bromodeoxyuridine (BrdU) and cigarette smoke, induces premature cell senescence. Recent evidence indicates that cellular senescence of various types of cells is accelerated in COPD patients. However, whether the senescence of airway epithelial cells contributes to the development of airway diseases is unknown. The present study was designed to test the hypothesis that premature senescence of airway epithelial cells (Clara cells) impairs repair processes and exacerbates inflammation after airway injury.</p> <p>Methods</p> <p>C57/BL6J mice were injected with the Clara-cell-specific toxicant naphthalene (NA) on days 0, 7, and 14, and each NA injection was followed by a daily dose of BrdU on each of the following 3 days, during which regenerating cells were allowed to incorporate BrdU into their DNA and to senesce. The p38 MAPK inhibitor SB202190 was injected 30 minutes before each BrdU dose. Mice were sacrificed at different times until day 28 and lungs of mice were obtained to investigate whether Clara cell senescence impairs airway epithelial regeneration and exacerbates airway inflammation. NCI-H441 cells were induced to senesce by exposure to BrdU or the telomerase inhibitor MST-312. Human lung tissue samples were obtained from COPD patients, asymptomatic smokers, and nonsmokers to investigate whether Clara cell senescence is accelerated in the airways of COPD patients, and if so, whether it is accompanied by p38 MAPK activation.</p> <p>Results</p> <p>BrdU did not alter the intensity of the airway epithelial injury or inflammation after a single NA exposure. However, after repeated NA exposure, BrdU induced epithelial cell (Clara cell) senescence, as demonstrated by a DNA damage response, p21 overexpression, increased senescence-associated β-galactosidase activity, and growth arrest, which resulted in impaired epithelial regeneration. The epithelial senescence was accompanied by p38 MAPK-dependent airway inflammation. Senescent NCI-H441 cells impaired epithelial wound repair and secreted increased amounts of pro-inflammatory cytokines in a p38 MAPK-dependent manner. Clara cell senescence in COPD patients was accelerated and accompanied by p38 MAPK activation.</p> <p>Conclusions</p> <p>Senescence of airway epithelial cells impairs repair processes and exacerbates p38 MAPK-dependent inflammation after airway injury, and it may contribute to the pathogenesis of COPD.</p

Identifying and Validating Tankyrase Binders and Substrates: A Candidate Approach.

The poly(ADP-ribose)polymerase (PARP) enzyme tankyrase (TNKS/ARTD5, TNKS2/ARTD6) uses its ankyrin repeat clusters (ARCs) to recognize degenerate peptide motifs in a wide range of proteins, thereby recruiting such proteins and their complexes for scaffolding and/or poly(ADP-ribosyl)ation. Here, we provide guidance for predicting putative tankyrase-binding motifs, based on the previously delineated peptide sequence rules and existing structural information. We present a general method for the expression and purification of tankyrase ARCs from Escherichia coli and outline a fluorescence polarization assay to quantitatively assess direct ARC-TBM peptide interactions. We provide a basic protocol for evaluating binding and poly(ADP-ribosyl)ation of full-length candidate interacting proteins by full-length tankyrase in mammalian cells

Diversity, Phylogeny and Expression Patterns of Pou and Six Homeodomain Transcription Factors in Hydrozoan Jellyfish Craspedacusta sowerbyi

Formation of all metazoan bodies is controlled by a group of selector genes including homeobox genes, highly conserved across the entire animal kingdom. The homeobox genes from Pou and Six classes are key members of the regulation cascades determining development of sensory organs, nervous system, gonads and muscles. Besides using common bilaterian models, more attention has recently been targeted at the identification and characterization of these genes within the basal metazoan phyla. Cnidaria as a diploblastic sister group to bilateria with simple and yet specialized organs are suitable models for studies on the sensory organ origin and the associated role of homeobox genes. In this work, Pou and Six homeobox genes, together with a broad range of other sensory-specific transcription factors, were identified in the transcriptome of hydrozoan jellyfish Craspedacusta sowerbyi. Phylogenetic analyses of Pou and Six proteins revealed cnidarian-specific sequence motifs and contributed to the classification of individual factors. The majority of the Craspedacusta sowerbyi Pou and Six homeobox genes are predominantly expressed in statocysts, manubrium and nerve ring, the tissues with sensory and nervous activities. The described diversity and expression patterns of Pou and Six factors in hydrozoan jellyfish highlight their evolutionarily conserved functions. This study extends the knowledge of the cnidarian genome complexity and shows that the transcriptome of hydrozoan jellyfish is generally rich in homeodomain transcription factors employed in the regulation of sensory and nervous functions

Eye Development under the control of SRp55/B52-Mediated Alternative Splicing of eyeless

The genetic programs specifying eye development are highly conserved during evolution and involve the vertebrate Pax-6 gene and its Drosophila melanogaster homolog eyeless (ey). Here we report that the SR protein B52/SRp55 controls a novel developmentally regulated splicing event of eyeless that is crucial for eye growth and specification in Drosophila. B52/SRp55 generates two isoforms of eyeless differing by an alternative exon encoding a 60-amino-acid insert at the beginning of the paired domain. The long isoform has impaired ability to trigger formation of ectopic eyes and to bind efficiently Eyeless target DNA sequences in vitro. When over-produced in the eye imaginal disc, this isoform induces a small eye phenotype, whereas the isoform lacking the alternative exon triggers eye over-growth and strong disorganization. Our results suggest that B52/SRp55 splicing activity is used during normal eye development to control eye organogenesis and size through regulation of eyeless alternative splicing