The histone H3/H4 chaperone CHAF1B prevents the mislocalization of CENP-A for chromosomal stability.

Restricting the localization of the evolutionarily conserved centromeric histone H3 variant CENP-A to centromeres prevents chromosomal instability (CIN). The mislocalization of CENP-A to non-centromeric regions contributes to CIN in yeasts, flies and human cells. Even though overexpression and mislocalization of CENP-A have been reported in cancers, the mechanisms responsible for its mislocalization remain poorly understood. Here, we used an imaging-based high-throughput RNAi screen to identify factors that prevent mislocalization of overexpressed YFP-tagged CENP-A (YFP-CENP-A) in HeLa cells. Among the top five candidates in the screen - the depletion of which showed increased nuclear YFP-CENP-A fluorescence - were the histone chaperones CHAF1B (or p60) and CHAF1A (or p150). Follow-up validation and characterization experiments showed that CHAF1B-depleted cells exhibited CENP-A mislocalization, CIN phenotypes and increased enrichment of CENP-A in chromatin fractions. The depletion of DAXX, a histone H3.3 chaperone, suppressed CENP-A mislocalization and CIN in CHAF1B-depleted cells. We propose that in CHAF1B-depleted cells, DAXX promotes mislocalization of the overexpressed CENP-A to non-centromeric regions, resulting in CIN. In summary, we identified regulators of CENP-A localization and defined a role for CHAF1B in preventing DAXX-dependent CENP-A mislocalization and CIN.

SuperMAP: Deep ultrafast MR relaxometry with joint spatiotemporal undersampling.

PURPOSE: To develop an ultrafast and robust MR parameter mapping network using deep learning. THEORY AND METHODS: We design a deep learning framework called SuperMAP that directly converts a series of undersampled (both in k-space and parameter-space) parameter-weighted images into several quantitative maps, bypassing the conventional exponential fitting procedure. We also present a novel technique to simultaneously reconstruct T1rho and T2 relaxation maps within a single scan. Full data were acquired and retrospectively undersampled for training and testing using traditional and state-of-the-art techniques for comparison. Prospective data were also collected to evaluate the trained network. The performance of all methods is evaluated using the parameter qualification errors and other metrics in the segmented regions of interest. RESULTS: SuperMAP achieved accurate T1rho and T2 mapping with high acceleration factors (R = 24 and R = 32). It exploited both spatial and temporal information and yielded low error (normalized mean square error of 2.7% at R = 24 and 2.8% at R = 32) and high resemblance (structural similarity of 97% at R = 24 and 96% at R = 32) to the gold standard. The network trained with retrospectively undersampled data also works well for the prospective data (with a slightly lower acceleration factor). SuperMAP is also superior to conventional methods. CONCLUSION: Our results demonstrate the feasibility of generating superfast MR parameter maps through very few undersampled parameter-weighted images. SuperMAP can simultaneously generate T1rho and T2 relaxation maps in a short scan time.

Effects of Heat Treatment on Interfacial Behavior and Bonding Strength of Surface Activated Bonding Ti-Al Laminate.

The surface activated bonding (SAB) method generally has the advantage of high bonding strength, low contact resistance, and high microstructural stability at room temperature. In this study, Ti-Al laminates were produced by surface activated bonding with aluminum and titanium foils. Heat treatment was conducted at the temperature range from 200 to 550 °C in vacuum. The bonding strength Ti-Al laminates was measured by a peel test, and the interfacial characteristics were investigated microstructural observation. The results showed that the bonding strength was the highest with heat treatment at 400 °C, microstructure observation revealed that the bonding strength of the Ti-Al laminate was influenced by the interfacial characteristics.

Influences of HLH-2 stability on anchor cell fate specification during Caenorhabditis elegans gonadogenesis.

The Caenorhabditis elegans E protein ortholog HLH-2 is required for the specification and function of the anchor cell, a unique, terminally differentiated somatic gonad cell that organizes uterine and vulval development. Initially, 4 cells-2 α cells and their sisters, the ß cells-have the potential to be the sole anchor cell. The ß cells rapidly lose anchor cell potential and invariably become ventral uterine precursor cells, while the 2 α cells interact via LIN-12/Notch to resolve which will be the anchor cell and which will become another ventral uterine precursor cell. HLH-2 protein stability is dynamically regulated in cells with anchor cell potential; initially present in all 4 cells, HLH-2 is degraded in presumptive ventral uterine precursor cells while remaining stable in the anchor cell. Here, we demonstrate that stability of HLH-2 protein is regulated by the activity of lin-12/Notch in both α and ß cells. Our analysis provides evidence that activation of LIN-12 promotes degradation of HLH-2 as part of a negative feedback loop during the anchor cell/ventral uterine precursor cell decision by the α cells, and that absence of lin-12 activity in ß cells increases HLH-2 stability and may account for their propensity to adopt the anchor cell fate in a lin-12 null background. We also performed an RNA interference screen of 232 ubiquitin-related genes and identified 7 genes that contribute to HLH-2 degradation in ventral uterine precursor cells; however, stabilizing HLH-2 by depleting ubiquitin ligases in a lin-12(+) background does not result in supernumerary anchor cells, suggesting that LIN-12 activation does not oppose hlh-2 activity solely by causing HLH-2 protein degradation. Finally, we provide evidence for lin-12-independent transcriptional regulation of hlh-2 in ß cells that correlates with known differences in POP-1/TCF levels and anchor cell potential between α and ß cells. Together, our results indicate that hlh-2 activity is regulated at multiple levels to restrict the anchor cell fate to a single cell.

IFATS collection: Selenium induces improvement of stem cell behaviors in human adipose-tissue stromal cells via SAPK/JNK and stemness acting signals.

In the present study, the potential of selenium to enhance stem cell behavior through improvement of human adipose tissue-derived stromal cells (ATSCs) and the associated molecular mechanism was evaluated. Selenium-induced improvement in stem cell behavior of human ATSCs caused expression of several genes, indicating downregulated mature cell marker proteins coupled with increased cell growth and telomerase activities after the overexpression of Rex1, Nanog, OCT4, SOX2, KLF4, and c-Myc. Also, selenium-treated ATSCs significantly downregulated p53 and p21 tumor suppressor gene products. Selenium induced active growth and growth enhanced by the activation of signal proteins in ATSCs via the inhibition of reactive oxygen species-mediated phospho-stress-activated protein kinase/c-Jun N-terminal protein kinase activation. The selenium-induced activation of extracellular regulated kinases 1/2 and Akt in ATSCs resulted in a subsequent induction of the expression of stemness transcription factors, particularly Rex1, Nanog, and Oct4, along with definitive demethylation on regulatory regions of Rex-1, Nanog, and Oct4. The results of our small interfering RNA knockdown experiment showed that Rex1 plays a major role in the proliferation of selenium-induced ATSCs. Selenium-treated ATSCs also exhibited more profound differentiation into mesodermal and neural lineages. We performed a direct comparison of gene expression profiles in control ATSCs and selenium-treated ATSCs and delineated specific members of important growth factor, signaling, cell adhesion, and transcription factor families. The observations of improved life span and multipotency of selenium-treated ATSCs clearly indicate that selenium-treated ATSCs represent an extraordinarily useful candidate cell source for tissue regeneration. Disclosure of potential conflicts of interest is found at the end of this article.

Krüppel-like factor 4 mediates cellular migration and invasion by altering RhoA activity.

Kru¨ppel like factor 4 (KLF4) is a transcription factor that regulates genes related to differentiation and proliferation. KLF4 also plays a role in metastasis via epithelial to mesenchymal transition. Here, we investigate the function of Klf4 in migration and invasion using mouse embryonic fibroblasts and the RKO human colon cancer cell line. Compared to wild-type, cells lacking Klf4 exhibited increased migration-associated phenotypes. In addition, overexpression of Klf4 in Klf4-/- MEFs attenuated the presence of stress fibers to wild-type levels. An invasion assay suggested that lack of Klf4 resulted in increased invasive capacity. Finally, analysis of RhoA showed elevated RhoA activity in both RKO and MEF cells. Taken together, our results strongly support the novel role of KLF4 in a post-translational regulatory mechanism where KLF4 indirectly modulates the actin cytoskeleton morphology via activity of RhoA in order to inhibit cellular migration and invasion.

Inhibitory effects of phenolic compounds from needles of Pinus densiflora on nitric oxide and PGE2 production.

The needles of Pinus densiflora Siebold et Zuccarini, a representative Pinus species that grows in Korea, have been used in oriental traditional medicine as remedies for rheumatitis, hemorrhage, cancer, etc. Phytochemical examination of the needles of Pinus densiflora Siebold et Zuccarini led to the isolation of four lignans, one flavan-3-ol, two flavonols and one organic acid. They were identified as icariside E(4) (1), cupressoside A (2), schizandriside (3), (+)-isolariciresinol (4), (+)-catechin (5), quercetin 3-O-ß-D-glucopyranoside (6), 5,7,8,4'-tetrahydroxy-3-methoxy-6-methylflavone 8-O-ß-D-glucopyranoside (7) and (-)-shikimic acid (8). In order to evaluate the anti-inflammatory effects of these compounds, their inhibitory activities against nitric oxide and prostaglandin E(2) production in IFN-γ- and lipopolysaccharide-stimulated RAW 264.7 cells were examined.